Tutorials/Catalyses

A catalyst is a stationary object (usually a still life) which can interact with an active reaction and later return to its original state. Catalysts are very useful in many applications, including conduits and hasslers. Here is an example of a stable catalyst:

x=11, y = 10, rule = LifeHistory 2.C$2.C$.2C6.2A$4.2A.A2.A$3.A.A.3A$A2.A.A$4A.3A$4.A3.A$2.A.A2.2A$2.2A ! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

The green still life interacts with the white object, and recovers to its original state by generation 15. In this tutorial, you'll learn the main types of catalyses and their applications. But first, we need to cover some important definitions.

Important terms

• Stable catalyst: a catalyst which is a still life. Most catalyses are of this form. In this tutorial we will only focus on stable catalyses, as periodic catalyses are as of now quite underdeveloped.
• Periodic catalyst: a catalyst which is an oscillator. These are generally considered "less useful" than stable catalysts, because a periodic catalyst usually does not work in every possible phase.
• Transparent catalyst or transparent object: an object which is destroyed completely (all of its cells being off at the same time) then restored (in the same position and with the same orientation)
• Pseudo-transparent catalyst: a catalyst that loses all of its cells but not at the same time (i.e. for each generation, at least one of its cells is alive)
• Recovery time: the time it takes for a catalyst to return back to its original state after interacting. In the example above, the recovery time is 15.
• Replacement catalyst: When a common catalyst fails, another, less common, catalyst must be used.
• Rock: A catalyst which does not lose any of its cells, even temporarily, during the interaction process. The snake-type catalyses below are examples of rocks.

Let's explore the different types of catalysts now!

Types of common catalyses

Fishhook (eater 1)

Here are some examples of fishhook catalyses:

x=28, y = 7, rule = LifeHistory 2.A8.2A7.A.A$A.C8.AC9.C$.AC8.AC7.2AC$4.2A8.2A8.2A$4.A.A7.A.A7.A.A$6.A 9.A9.A$6.2A8.2A8.2A! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

The marked white cells should always be on in a fishhook-type catalyst. Sometimes, the fishhook may engage in a more unusual manner, but these are rarer:

x=21, y = 6, rule = B3/S23 o3b2o8b2o$2ob2o8b2o$3bo3b2o4bo3b2o$7bobo7bobo$9bo9bo$9b2o8b2o! [[ THEME 6 GRID THUMBNAIL THUMBSIZE 2 ]]

In the left example, the fishhook later catalyses a blinker. This catalysis is often useful.

Even rarer is when the tail of the fishhook is to be used as a rock (the red cells must not be born):

x=22, y = 7, rule = LifeHistory 6.2A12.2A$7.A13.A$4.3A11.3A$3.DA12.DA$4.D13.D$.3C11.3C$A3.2A8.A2.2A! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

Recognizing when to use a fishhook catalysis is really a matter of experience. For practice, try placing an eater 1 somewhere within this blue field to eat the middleweight spaceship (click on the thumbnail below to draw cells in LifeViewer using the pencil icon):

x=18, y = 9, rule = LifeHistory .5A$A4.A$5.A4.8B$A3.A5.8B$2.A7.8B$10.8B$10.8B$10.8B$10.8B! [[ GRID THUMBNAIL THUMBSIZE 2 WIDTH 800 HEIGHT 600 ]]

Block

Here are some examples of block catalyses:

x=18, y = 7, rule = LifeHistory .A14.A$A.A5.3A6.A$A.A5.3A3.A.A$.C7.C5.C2$.2A5.2A4.2A$.2A5.2A4.2A! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

Block catalyses typically occur when there is a one cell leading edge of a pattern, shown in white above.

They are usually much easier to recognize than fishhook-type catalyses, however they may sometimes fail:

x=12, y = 6, rule = B3/S23 10b2o$ob2o5b2o$bo7bo2$b2o6b2o$b2o6b2o! [[ THEME 6 GRID THUMBNAIL THUMBSIZE 2 ]]

Moving the block over by one cell often fixes this problem:

x=12, y = 6, rule = B3/S23 10b2o$ob2o5b2o$bo7bo2$2o6b2o$2o6b2o! [[ THEME 6 GRID THUMBNAIL THUMBSIZE 2 ]]

There are several more complicated block catalyses involving a two-cell leading edge. In that case, an eater 1 will also work.

x=246, y = 14, rule = B3/S23 184bo58b3o$14b2o37bo36bobo88b4o43b4o$13bo10b2o4bo5bo11bo3b2o29bo6b2o51b o35bo$12bo11bo7bo2b3o4b2o5b2o4bo20bo14bo40bo9b2o11b2o11bo4bobo2b2o11b o5bobo3b2o4bo6bo4bo21bo$2o2bo22b2obo6bo2bo2bo10bo4b2o3bo7b3o2bo5b4obo 6b4obo8bo3bo6b2o9bob4o2bo2b2ob4o2bo4b2o2bo8b2ob2o4b2ob4o2bo2bo2b2ob2o 6b2ob2o8b2ob2obo4b6o5b6o$b4o8b4o8b4o3bo4b4o8b4obo6b4o8b4o8b4o8b4o8b4o 8b4o5bo2b4o2bo2bo2b4o2bo5b4o8b4o5bo2b4obo4bob4o8b4o8b4o8b4o8b4o$105bo 32bo11bo35bo3bo$104bobo$b2o10b2o10b2o10b2o10b2o10b2o10b2o10b2o10b2o6b o3b2o10b2o10b2o10b2o10b2o10b2o10b2o10b2o10b2o10b2o10b2o10b2o$b2o11bo11b o7bo3bo7bo3bo10b2o10b2o11bo11bo10b2o11bo10b2o10b2o10b2o10b2o9bobo9bob o10b2o10b2o11bo10b2o$11b3o9b3o8b4o8b4o33b3o9b3o21b3o59bo11bo33b3o$11b o11bo59bo11bo23bo107bo$34b2o12b2o$34b2o12b2o! [[ THEME 6 GRID THUMBNAIL THUMBSIZE 2 ]]

As practice, try to eat this bun with a block placed in the blue region:

x=12, y = 6, rule = LifeHistory 6B$6B$6B2.3A$6B2.A2.A$6B3.2A$6B! [[ GRID THUMBNAIL THUMBSIZE 2 WIDTH 800 HEIGHT 600 ]]

Boat

Boat catalyses are rarer, but are still useful. Here are two examples:

x=22, y = 10, rule = LifeHistory 16.A$16.2A$15.2A2$.2A$2CB16.2DB2$.A18.A$A.A16.A.A$2A17.2A! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

They typically occur when there is a two cell leading edge, which is marked. Boat catalyses fail very often, so see the "Replacement catalysts" section below for potential replacement catalysts. As a general rule, boats are most likely to succeed when a cell adjacent to the leading edge (shown in blue) will turn on in the following generation.

There is a secondary boat catalysis that works on objects with a line of three or more cells, but it's important here that the red cell does not turn on:

x=22, y = 6, rule = LifeHistory 3.A3.A10.A$6.A$2.D3C11.D4C$.A14.A$A.A12.A.A$2A13.2A! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

The boat also has a tertiary catalysis:

x=8, y = 7, rule = B3/S23 b2o$obo$bo$4bo$2b2obo$2b2obo$3bo3bo! [[ THEME 6 GRID THUMBNAIL THUMBSIZE 2 ]]

Snake

Snake catalyses are examples of rocks, or catalysts which do not change even temporarily when interacting with an object. They must function this way due to the fact that the two cells in the center would die from overpopulation due to already having three live neighbors.

Three example snake catalysts are shown below. The white cells should always be on to trigger the important next generation, where the snake functions as a rock:

x=24, y = 9, rule = LifeHistory 15.A6.A$4.A8.2A8.A$2A.2A6.2A7.A.2A$.C9.C9.C2$2.2A8.2A8.2A$3.A9.A9.A$ 2.A9.A9.A$2.2A8.2A8.2A! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

Both the head and tail of a fishhook can function as a snake catalyst:

x=26, y = 8, rule = LifeHistory A9.A9.A$.A.3A5.A.3A5.A.3A$2.C9.C9.C2$3.2A8.2A8.2A$4.A9.A9.A$3.A10.A.A 4.3A$3.2A10.2A4.A! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

Conduit 1 is an example of a conduit using a snake catalyst. Try to catalyze the reaction below with a snake in the blue field (as a hint, the cell which should trigger the rock interaction is marked):

x=15, y = 7, rule = LifeHistory 7B$7B4.2A.A$7B5.3A$7B6.A$7BD$7B4.2A$7B4.2A! [[ GRID THUMBNAIL THUMBSIZE 2 WIDTH 800 HEIGHT 600 ]]

Tub

Non-rock tub catalyses can be tricky to find, but they are most likely to work when the frontend of the active reaction is two or three cells long, like one of the examples below:

x=45, y = 73, rule = LifeHistory 25.A$4.A5.A10.A3.A12.A4.A$3A5.A.A15.A7.A.2A3.3A$3A5.3A7.3A6.2A6.2A3.4A 2$2.A7.A7.A7.A7.A7.A$.A.A5.A.A5.A.A5.A.A5.A.A5.A.A$2.A7.A7.A7.A7.A7.A 4$21.A2$21.A2$18.A2.A2.A2$19.A.A.A2$21.A3$.A7.A15.2A10.A5.A$A.2A4.A.2A 7.2A5.2A8.2A2.A3.A$A.A5.A.A8.A7.A7.3A2.A2.A$2.C7.C7.C8.C7.C7.C$2.A7.A 7.A7.A7.A7.A$.A.A5.A.A5.A.A5.A.A5.A.A5.A.A$2.A7.A7.A7.A7.A7.A4$21.A2$ 21.A2$18.A2.A2.A2$19.A.A.A2$21.A3$.2A6.2A14.3A8.2A$A.2A4.A.2A7.2A4.A. A7.A2.A4.2A$2.A7.A7.3A6.2A6.A.A5.2A$2.2C6.2C6.2C6.2C6.2C6.2C$.2AC5.2A C5.2AC6.AC6.AC6.AC$.A.A5.A.A5.A.A5.A.A5.A.A5.A.A$2.A7.A7.A7.A7.A7.A4$ 21.A2$21.A2$18.A2.A2.A2$19.A.A.A2$21.A4$26.A$.3A5.3A13.A.A8.2A$3.A7.A 6.A.A4.A9.A2.A4.2A$28.A6.A2$.A2.A4.A2.A4.A2.A4.A2.A4.A2.A4.A2.A$.A.A5. A.A5.A.A5.A.A5.A.A5.A.A$2.A7.A7.A7.A7.A7.A! [[ GRID THUMBNAIL THUMBSIZE 2 WIDTH 500 HEIGHT 700 ]]

The reactions start differently but end up the same way through the same general mechanism:

• On generation 1, one cell (marked in white) is born next to the tub;
• On generation 2, two more cells are born next to the tub. This causes the three white cells to die;
• By generation 3, the cells in the center have died and what remains is a 5-cell parent of the tub. In all tub catalyses, the tub should turn into this 5-cell parent.

The tub has a secondary catalysis where it acts as a rock. For it to work, there must be a line of four or more cells, and the cell marked in blue must turn on in the next generation.

x=65, y = 8, rule = LifeHistory .A14.A11.A12.A$A.A12.A.A9.A.A10.A.A17.A$.A14.A11.A12.A17.A.A$60.A$.B 4C10.B4C7.B4C8.B6C$2A14.2A9.2A4.2A5.2A5.2A9.A.B4C$15.A42.2A.A$16.A! [[ GRID THUMBNAIL THUMBSIZE 2 WIDTH 800 HEIGHT 600 ]]

Thirdly, the tub has a very specific use where it can eat a fully formed beacon. Parity is not a concern, as the reaction only begins when the beacon is in its dense phase.

x = 22, y = 22, rule = B3/S23 bo7bobo$obo4bo3bo$bo5bo$6bo4bo8b2o$7bo12b2o$7bo3bo$3bo5bobo$b2ob2o2$o 5bo2$2obob2o9$3b2o$3b2o! #C [[ THUMBSIZE 2 THEME 6 GRID GRIDMAJOR 0 SUPPRESS THUMBLAUNCH ]] #C [[ GPS 8 THUMBSIZE 2 ]]

A tub eating a beacon in a p30 oscillator. (click above to open LifeViewer)

Ship

Observe the following reaction:

x=7, y = 9, rule = B3/S23 bo$o$2o$2b3o3$4b2o$4bobo$5b2o! [[ THEME 6 GRID THUMBNAIL THUMBSIZE 2 ]]

The ship is turned into a relative of the I-heptomino (specifically a great-uncle) then is turned back into a ship by a perfectly-timed temporary induction. The ship rarely recovers by its own, but it's worth trying because it has replacement catalysts that recover much more often.

Replacement catalyses

So, you've tried to catalyze a reaction, but the common catalyst fails! Luckily for you, this is not a complete disaster, since many replacement catalysts exist exactly to assist you when your fishhook or block doesn't just work out.

Fishhook replacements

The most common way for a fishhook to fail is something like this:

x=8, y = 8, rule = B3/S23 o$o2bo$b3o2$4b2o$4bobo$6bo$6b2o! [[ THEME 6 GRID THUMBNAIL THUMBSIZE 2 ]]

Luckily, this is also the easiest to fix. Simply flip the eater 1 around and it works!

x=32, y = 9, rule = B3/S23 o15bo$o2bo20bo$b3o14bo5bo2bo$25b3o$4b2o4bobobobobobo$4bobo21b2o$6bo11b o9bo$6b2o21b3o$16bo14bo! [[ THEME 6 GRID THUMBNAIL THUMBSIZE 2 ]]

This was a bit cheating, however. Sometimes, we need a genuinely new catalyst. Here are two almost-catalyses where the fishhook almost recovers, but an extra spark destroys it or an extra cell gets attached to its recovering phase:

x=20, y = 8, rule = B3/S23 12bo$o10bobo$b2o10b2o$2o12bo$4b2o7bo2b2o$4bobo9bobo$6bo11bo$6b2o10b2o! [[ THEME 6 GRID THUMBNAIL THUMBSIZE 2 ]]

The most common replacement catalyst for a fishhook is the handy eater 2. An eater 2 recovers differently from an eater 1, making it more versatile (and its symmetry means that it can eat from two directions). It can handle both of our problems:

x=23, y = 11, rule = B3/S23 12bo$o10bobo$b2o10b2o$2o12bo$4b2obo5bo2b2obo$4b2ob3o6b2ob3o$10bo11bo$ 4b2ob3o6b2ob3o$5bobo9bobo$5bobo9bobo$6bo11bo! [[ THEME 6 GRID THUMBNAIL THUMBSIZE 2 ]]

There are many, many more cases in which neither an eater 1 nor an eater 2 works. This guide, by Entity Valkyrie and MathAndCode, addresses many of these:

x=3135, y = 81, rule = EV2QuadColor 25.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61. 3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F. 3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F. 3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61. 3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F. 3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F. 3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F$ 25.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F61.F3.F3. F.F61.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F61.F3. F3.F.F61.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F61. F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F 61.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F61.F3.F3. F.F61.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F61.F3. 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(Note: Patterns for replacement guide shown here and below are in a custom multistate rule designed for annotating purposes. Please go to the link and copy/paste the rule tree definition in Golly first, before copying the pattern from LifeViewer and pasting in Golly.)

Block replacements

Sometimes, a block that fails only needs to be supported with another catalyst, not replaced entirely. Take this partial PT9B, for example:

x=9, y = 9, rule = LifeHistory 2.2A$2.2A2$5.3D2$7.2A$.3A3.2A$.A.A$.A.A! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

The catalyst almost works, but then an extra blinker, shown in red, destroys it. If only we could get rid of that blinker...

Luckily, we can use what we just learned in this tutorial. Adding an extra fishhook suppresses the blinker and allows the catalyst to work:

x=12, y = 10, rule = B3/S23 11bo$2b2o5b3o$2b2o4bo$8b2o3$7b2o$b3o3b2o$bobo$bobo! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

This trick works in a variety of circumstances where a block fails because unwanted cells are born to one side. Also, the fishhook can often be replaced by a block. This sometimes works even if a fishhook doesn't work.

x=185, y = 44, rule = B3/S23 98bo$99bo16b2o11b4o$3bo43bo19bo13b2o15b2o18bo7b2o21bo$2b2o14b2o27bo18b o14b3o10b3ob2o14b2o3bo7bo17b2obo14bo12bo2b2o$2b2o12bob2o12bo16bobo13b o14bob2o12bobo13bo14bo18b3o13b3o11b2o$3o13b3o13b3o14bobo13bobo12b3o13b 3o14bobo12b3o15b2o13bobo13bobo$bo15bo15bo16bo15bo14bo15bo16bo14bo15bo 16bo15bo2$b2o14b2o14b2o14b2o14b2o14b2o14b2o14b2o14b2o14b2o14b2o14b2o$ b2o14b2o14b2o14b2o14b2o14b2o14b2o14b2o14b2o14b2o14b2o14b2o8$98bo$99bo 16b2o11b4o$3bo43bo19bo13b2o15b2o18bo7b2o21bo$2b2o14b2o27bo18bo14b3o10b 3ob2o14b2o3bo7bo17b2obo14bo12bo2b2o$2b2o12bob2o12bo16bobo13bo14bob2o12b obo13bo14bo18b3o13b3o11b2o$3o13b3o13b3o14bobo13bobo12b3o13b3o14bobo12b 3o15b2o13bobo13bobo$bo15bo15bo16bo15bo14bo15bo16bo14bo15bo16bo15bo2$b 2o14b2o14b2o14b2o14b2o14b2o14b2o14b2o14b2o14b2o14b2o14b2o$b2o2b2o10b2o 2b2o10b2o2b2o10b2o2b2o10b2o2b2o10b2o2b2o10b2o2b2o10b2o2b2o10b2o2b2o10b 2o2b2o10b2o2b2o10b2o2b2o$5bobo13bobo13bobo13bobo13bobo13bobo13bobo13b obo13bobo13bobo13bobo13bobo$7bo15bo15bo15bo15bo15bo15bo15bo15bo15bo15b o15bo$7b2o14b2o14b2o14b2o14b2o14b2o14b2o14b2o14b2o14b2o14b2o14b2o5$98b o$99bo16b2o11b4o$3bo43bo19bo13b2o15b2o18bo7b2o21bo$2b2o14b2o27bo18bo14b 3o10b3ob2o14b2o3bo7bo17b2obo14bo12bo2b2o$2b2o12bob2o12bo16bobo13bo14b ob2o12bobo13bo14bo18b3o13b3o11b2o$3o13b3o13b3o14bobo13bobo12b3o13b3o14b obo12b3o15b2o13bobo13bobo$bo15bo15bo16bo15bo14bo15bo16bo14bo15bo16bo15b o$5b2o14b2o14b2o14b2o14b2o14b2o14b2o14b2o14b2o14b2o14b2o14b2o$b2o2b2o 10b2o2b2o10b2o2b2o10b2o2b2o10b2o2b2o10b2o2b2o10b2o2b2o10b2o2b2o10b2o2b 2o10b2o2b2o10b2o2b2o10b2o2b2o$b2o14b2o14b2o14b2o14b2o14b2o14b2o14b2o14b 2o14b2o14b2o14b2o! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

Also, if the fishhook recovers too quickly but otherwise works, then like other examples where a fishhook recovers too quickly but otherwise works, it can sometimes be replaced with an eater 2.

x=33, y = 17, rule = B3/S23 2b3o16b3o2$o18bo$obo16bobo$o18bo5$3b2o17b2o$3b2o2b2o13b2o2b2obo$7bobo 16b2ob3o$9bo22bo$9b2o15b2ob3o$27bobo$27bobo$28bo! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

Another example where a block catalyst can be fixed by supporting the block with another catalyst comes from the following example, where the block is turned into a first cousin of the century then crashes into a boat.

x=5, y = 8, rule = B3/S23 b2o$b2o3$3o$obo$3bo$4bo! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

In this case, the block can be supported by another block. In fact, two positions work.

x=24, y = 8, rule = B3/S23 5b2o13b2o$2o3b2o13b2o$2o13b2o$15b2o$4b3o12b3o$4bobo12bobo$7bo14bo$8bo14bo! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

This trick only works if there is something for the century cousin to crash into (and even then, not always), but luckily, there is an actual replacement catalyst for when the block is turned into a century cousin with nothing to hit. (It also works in the above example if one does not need to get rid of the boat.)

x=19, y = 10, rule = B3/S23 o11bo$b3o9b3o$2bo11bo2$2b2o10b2o2bo$2b2o9bob4o$11b3o$10bo3b3o$11b3o2bo$13bo!5b2o13b2o$2o3b2o13b2o$2o13b2o$15b2o$4b3o12b3o$4bobo12bobo$7bo14bo$8bo14bo! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

There is another replacement catalyst for when the block is turned into a tail.

x=22, y = 14, rule = B3/S23 3bo15bo$3bo15bo$3bo15bo$3bo15bo$3o13b3o$bo15bo2$b2o14b2o$b2o12bo2bo$15b 2obobo$18b2obo$15b3o3bo$15bo2b3o$18bo! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

It should be noted that when a block fails in one of the most recent two ways, it can often be replaced with a hook with tail (although the hook with tail is not a replacement catalyst for the block in the strictest sense).

x=17, y = 25, rule = B3/S23 15bo$15bo$15bo$o14bo$b3o8b3o$2bo10bo2$2b2o9b2o$2b2o9b2o6$15bo$15bo$15b o$o14bo$b3o8b3o$2bo10bo2$bobo8bobo$b2obo7b2obo$4bo10bo$4b2o9b2o! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

If a block is turned into a crotchet in a certain way, it can be replaced with a boat—or a fishhook bridge fishhook.

x=32, y = 9, rule = B3/S23 bo10bo10bo$4obo5b4obo5b4obo$4bo10bo10bo2$4b2o9b2o9b2o$4b2o9bobo8bobo$ 16bo7bobob3o$24b2o5bo$30b2o! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

There is another replacement catalyst for another way in which the block is sometimes turned into a crotchet.

x=20, y = 13, rule = B3/S23 obo11bobo$b2o12b2o$3bobo11bobo$3bobo11bobo$4bo13bo2$3b2o12b2o$3b2o12b 2o$14bo$14b5o$18bo$16bo$16b2o! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

Sometimes, the block becomes a crotchet when it is sparked by a domino when it is a pre-block.

x=10, y = 34, rule = LifeHistory 2C2.6A$2C.A$.D2.5A28$2C2.6A$2C.A$.D2.5A$9.A! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

Two fishhooks can be used in that case.

x=12, y = 39, rule = LifeHistory 2A$.A$.A.A$2.2A2.6A$5.A$2.2A2.5A$.A.A$.A$2A22$2A$.A$.A.A$2.2A2.6A$5.A $2.2A2.5A$.A.A7.A$.A$2A! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

In addition, there is a fourth way in which a block is sometimes turned into a crotchet. In this case, it can be replaced with a claw with tail supported by a fishhook.

x=21, y = 10, rule = B3/S23 3bo13bo$3bo13bo$obo11bobo$bo13bo2$b2o12b2o$b2o8b2o2bo2bo$10bobo3b2obo $10bo8bo$9b2o8b2o! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

This also works if it's turned into a tail.

x=21, y = 10, rule = B3/S23 2bo13bo$3bo13bo$obo11bobo$bo13bo2$b2o12b2o$b2o8b2o2bo2bo$10bobo3b2obo $10bo8bo$9b2o8b2o! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

For one particular type of block catalysis (specifically where the block is turned into a grin but not through the six-cell grin parent in pentoad 2), the block can be replaced with a long hook with tail. For example, if a block is used with the eater 5 (which will be explained next) in this case, the chaos hits and destroys it (then destroys the tub with tail).

x=9, y = 10, rule = B3/S23 4bo$3bo3b2o$4bo2b2o$5b2o$2o$2o3bo$4bobo$5bobo$7bo$7b2o! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

Replacing the block with a long hook with tail avoids this.

x=10, y = 11, rule = B3/S23 5bo$4bo3b2o$5bo2b2o$6b2o2$b2o3bo$bo3bobo$2bo3bobo$3bo4bo$3o5b2o$o! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

A relatively common problem encountered is when a block tries to catalyse in a certain way but becomes nothing but a heavyweight spark:

x=4, y = 8, rule = B3/S23 b2o$b3o$2bo$2o$o2$2o$2o! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

In that case, this catalyst can be used instead, but it only works if there are no additional cells attached to the heavyweight spark:

x=15, y = 15, rule = B3/S23 7b2o$7b3o$8bo$6b2o$6bo2$6b2o2b2o$6b2o3bo$2o9bob2o$o2bo6b2o2bo$2b2o2bo 5b2o$3bobobo2b2o$3bo2bobo2bo$4bobob2o$5bo! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

Occasionally, a block will become a U-turner when it eats something but fails to recover.

4bobo$2obo2bo$2o2bo$6bo$6bobo! #C [[ THUMBSIZE 2 THEME 6 GRID GRIDMAJOR 0 SUPPRESS THUMBLAUNCH ]] #C [[ GPS 4 THUMBSIZE 2 STOP 4 ]]

(click above to open LifeViewer)

In that case, the block can be restored with another block and a boat:

6b2o$5bobo$6bo3$2o6bobo$2o2b2obo2bo$4b2o2bo$10bo$10bobo! #C [[ THUMBSIZE 2 THEME 6 GRID GRIDMAJOR 0 SUPPRESS THUMBLAUNCH ]] #C [[ GPS 10 THUMBSIZE 2 ]]

(click above to open LifeViewer)

Here is a block replacement guide by Entity Valkyrie and MathAndCode:

x=1333, y = 81, rule = EV2QuadColor 26.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61. 3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F. 3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F.3F61.3F.3F. 3F$26.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F61.F3. F3.F.F61.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F61. F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F61.F3.F3.F.F 61.F3.F3.F.F61.F3.F3.F.F$26.F3.2F2.F.F61.F3.2F2.F.F61.F3.2F2.F.F61.F3. 2F2.F.F61.F3.2F2.F.F61.F3.2F2.F.F61.F3.2F2.F.F61.F3.2F2.F.F61.F3.2F2. F.F61.F3.2F2.F.F61.F3.2F2.F.F61.F3.2F2.F.F61.F3.2F2.F.F61.F3.2F2.F.F61. F3.2F2.F.F61.F3.2F2.F.F61.F3.2F2.F.F61.F3.2F2.F.F61.F3.2F2.F.F$26.F.F .F3.F.F61.F.F.F3.F.F61.F.F.F3.F.F61.F.F.F3.F.F61.F.F.F3.F.F61.F.F.F3. F.F61.F.F.F3.F.F61.F.F.F3.F.F61.F.F.F3.F.F61.F.F.F3.F.F61.F.F.F3.F.F61. F.F.F3.F.F61.F.F.F3.F.F61.F.F.F3.F.F61.F.F.F3.F.F61.F.F.F3.F.F61.F.F. F3.F.F61.F.F.F3.F.F61.F.F.F3.F.F$26.3F.3F.F.F61.3F.3F.F.F61.3F.3F.F.F 61.3F.3F.F.F61.3F.3F.F.F61.3F.3F.F.F61.3F.3F.F.F61.3F.3F.F.F61.3F.3F. F.F61.3F.3F.F.F61.3F.3F.F.F61.3F.3F.F.F61.3F.3F.F.F61.3F.3F.F.F61.3F. 3F.F.F61.3F.3F.F.F61.3F.3F.F.F61.3F.3F.F.F61.3F.3F.F.F2$30.F.F69.F.F69. F.F69.F.F69.3F69.3F69.F.F69.F.F69.3F69.3F69.3F69.F.F69.3F69.3F69.3F69. 3F69.3F69.3F69.3F$30.F.F69.F.F69.F.F69.F.F71.F71.F69.F.F69.F.F71.F69. F.F69.F71.F.F71.F69.F73.F69.F71.F71.F73.F$30.3F69.3F69.3F69.3F71.F69. 3F69.3F69.3F69.3F69.3F69.3F69.3F69.3F69.3F69.3F69.3F69.3F69.3F69.3F$32. F71.F71.F71.F71.F69.F73.F71.F69.F71.F.F69.F.F71.F69.F71.F.F69.F73.F71. F71.F71.F$32.F71.F71.F71.F71.F69.3F71.F71.F69.3F35.2D32.3F69.3F71.F69. 3F69.3F69.3F69.3F69.3F69.3F69.3F$142.D503.D$143.3D497.D.D217.2D$644.D 220.D$19.H71.H71.H71.H71.H71.H71.H71.H71.H71.H71.H71.H51.D19.H71.H71. H71.H71.H71.H71.H$19.2H47.D22.2H70.2H70.2H70.2H70.2H70.2H70.2H70.2H70. 2H70.2H70.2H49.2D19.2H70.2H50.D19.2H7.A40.D.D19.2H70.2H46.D23.2H51.2D 17.2H$2D13.7H46.D3.2D13.7H50.2D13.7H65.7H49.2D14.7H8.2A55.7H7.3A41.D13. 7H49.2D14.7H65.7H9.A38.3D14.7H9.A40.2D13.7H9.A40.2D13.7H6.3A38.D2.D14. 7H9.A55.7H8.2A37.D3.D13.7H4.2A3.A39.D15.7H65.7H46.D18.7H47.D2.3D12.7H 9.A$.2D.2E9.8H8.2E37.D2.2D.2E9.8H8.2E36.2D2.2D.2E9.8H8.2E39.2D2.2E9.8H 6.A.2E39.2D2.2E9.8H9.E40.D2.2E9.8H8.FE40.2D.2E9.8H7.A2E40.D2.2E9.8H7. A2E40.D2.2E9.8H8.FE37.D2.D2.2E9.8H8.FE41.D.2E9.8H8.FE37.2D.2D.2E9.8H8. 2E38.D.D2.2E9.8H3.A4.FE39.D3.2E9.8H8.FE36.D3.2D.2E9.8H8.FE40.D2.2E9.8H 8.2E38.D.D2.2E9.8H8.2E35.2D.D.D2.2E9.8H8.2E37.D2.2D.2E9.8H8.FE$.D2.2E 9.7H9.FE37.D2.D2.2E9.7H9.FE38.3D2.2E9.7H6.A2.FE38.D2.D.2E9.7H5.A3.FE41. D.2E9.7H9.FE40.2D.2E9.7H9.FE40.D2.2E9.7H9.FE41.D.2E9.7H9.FE41.D.2E9.7H 9.FE41.D.2E9.7H8.AFE39.2D2.2E9.7H9.FE40.D2.2E9.7H9.FE41.D.2E9.7H5.A3. 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[[ THUMBNAIL THUMBSIZE 2 WIDTH 1200 HEIGHT 400 ]]

Boat replacements

Here is an example of a boat in need:

x=3, y = 8, rule = LifeHistory .A$2.A$3A2$D$.A$A.A$.2A! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

In this example, the white cell at generation 4 gets turned on when it shouldn't. We have a fix for this, as usual. Replace the boat with a tub with tail and block (this catalyst is called an eater 5 or tub-with-tail eater):

x=9, y = 10, rule = B3/S23 5bo$6bo$4b3o2$2o$2o3bo$4bobo$5bobo$7bo$7b2o! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

Boats can also fail much more spectacularly:

x=8, y = 4, rule = B3/S23 6bo$3o2bobo$obo3b2o$obo! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

In this case, the boat can be replaced by this (often called the "gourmet catalyst" due to its use in gourmet):

x=10, y = 10, rule = B3/S23 8b2o$7bobo$7bo$6b2o2$6b2o$3o2bobo$obo3bo$obo4b3o$9bo! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

Note that this doesn't always work, since it requires a spark to recover properly.

These replacement catalysts also work for failed tertiary boat catalyses. Here are two examples:

x=34, y = 29, rule = B3/S23 6b2o18b2o$5bobo17bobo$6bo19bo$29bo$7b4o16b2obo$8b2o17b2obo$10bo16bo4b o$9bo17bo4bo$8bo24bo10$7b2o10b2o6b2o$7bo11bo7bo$5bobo12b3ob2obo$4bobo 15bobobo$2o3bo19bo$2o26bo$6b4o16b2obo$7b2o17b2obo$9bo16bo4bo$8bo17bo4b o$7bo24bo! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

For the secondary boat catalysis, there will sometimes be a blinker next to the boat when it recovers that then destroys the boat.

x=31, y = 6, rule = B3/S23 3bo11bo10bo$3bo11bobo9bo2bo$3bo2bo8bo11bobo$bo3b2o6bo11bo4bo$obo3bo5b obo9bobo3bo$2o10b2o10b2o4bo! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

When this happens, the boat can be replaced with a beehive with tail.

x=34, y = 8, rule = B3/S23 6bo11bo10bo$6bo11bobo9bo2bo$6bo2bo8bo11bobo$3b2o3b2o5b2o10b2o4bo$2bo2b o3bo4bo2bo8bo2bo3bo$bob2o8bob2o8bob2o4bo$bo11bo11bo$2o10b2o10b2o! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

This also works if the part of the blinker that is farther away from the boat is modified.

x=20, y = 10, rule = B3/S23 7bo11bo$5b2o10b2o$3bo11bo$3bo11bo$3bobo9bobo$bo10b2o$obo8bo2bo$2o8bob 2o$10bo$9b2o! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

A beehive with tail can almost always be replaced with an (inducted) bun or a thirteen loop.

x=41, y = 36, rule = B3/S23 24bo$22b2o15bo$5bo14bo13bo4bo$6bo2bo10bo13bobobobo$6bobo11bobo11bo3bo $3b2o4bo7b2o12b2o$2bo2bo3bo6bo2bo10bo2bo$bob2o4bo5bob2o10bob2o$bo13bo 13bo$2o12b2o12b2o4$24bo$22b2o15bo$5bo14bo13bo4bo$6bo2bo10bo13bobobobo $6bobo11bobo11bo3bo$3b2o4bo7b2o12b2o$2bo2bo3bo6bo2bo10bo2bo$2b3o4bo6b 3o11b3o2$2b3o11b3o11b3o$2bo2bo10bo2bo10bo2bo$3b2o12b2o12b2o2$24bo$22b 2o15bo$5bo14bo13bo4bo$6bo2bo10bo13bobobobo$2o4bobo5b2o4bobo5b2o4bo3bo $o2b2o4bo4bo2b2o9bo2b2o$b2o2bo3bo5b2o2bo9b2o2bo$4bo4bo8bo13bo$b3o11b3o 11b3o$bo13bo13bo! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

This is sometimes useful to know for welding purposes, such as placing a Snark close to a succeeding syringe with a xs15_3lkia4z32.

x=44, y = 40, rule = B3/S23 12b2o$12bobo$14bo4b2o$10b4ob2o2bo2bo$10bo2bobobobob2o$13bobobobo$14b2o bobo$18bo2$4b2o$5bo7b2o$5bobo5b2o$6b2o4$34bo$32b3o$31bo$16b2o13b2o$16b o$17b3o$20bo$17b2o2bo$16bo2b2o$16b2o16b2o$bo32b2o$b2o$obo5$37b2obo$37b 2ob3o$43bo$37b2ob3o$38bobo$26b2o10bobo$26b2o11bo! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

Occasionally, a boat will have an extra cell at generation 2 that turns it into a Wing predecessor:

x=9, y = 5, rule = B3/S23 o$bo3bo$2b3o2bo$6bobo$7b2o! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

When this happens, the boat can be replaced with a 21-cell catalyst consisting of an Eater bridge eater and a beehive.

x=16, y = 8, rule = B3/S23 8b2o$8bobob2obo$10bobob2o$o9bobo$bo3bo5b2o$2b3o2b2o$6bo2bo$7b2o! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

Snake replacements

Sometimes, the snake needs to be replaced them with a similar catalyst which does the same thing but might have better clearance. For example, if a snake is required to be in close proximity to a fishhook, the fishhook's interaction might destroy the snake (and subsequently the fishhook). In this case from the conduit L112, replacing the snake with a higher-clearance second fishhook (or aircraft carrier) can prevent the interaction:

x=51, y = 9, rule = B3/S23 7bo26bo14bo$2o4bo20b2o4bo8b2o4bo$bo4b3o8bo10bo4b3o7bo4b3o$o18bo5b3o13b o$2o23bo15b2o$3b2o6bobobobobobo8b2o13b2o$4bo26bo14bo$b3o15bo8b3o12b3o$ bo15bo10bo14bo! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

A problem that sometimes occurs with snake catalyses is that a certain cell above the snake (marked in red) will be born when the snake is supposed to be done interacting. When this happens, try replacing the snake with a hook with tail.

x=18, y = 19, rule = LifeHistory 2A.2A8.3A$2.C.D9.C.D2$3.2A10.2A$4.A11.A$3.A11.A$3.2A10.2A6$2A.2A8.3A$ 2.C.D9.C.D2$.A.A9.A.A$.2A.A8.2A.A$4.A11.A$4.2A10.2A! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

Tub replacements

Sometimes, a single dot at the end of the tub parent is replaced with a line of three cells, causing the tub to turn into a block instead of recovering:

x=24, y = 12, rule = LifeHistory 22.2A$21.2A$20.2A$A5.A2$.2A.2A$3.A$6.D15.D$6.D15.D$4.A15.A$3.A.A13.A. A$4.A15.A! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

When this occurs, the tub should be replaced with this catalyst with a regenerative loop motif:

x=30, y = 18, rule = B3/S23 23b2o$22b2o$21b2o$bo5bo2$2b2ob2o$4bo3$5bo15bo$4bobo13bobo$3bobo13bobo$ b3o2b3o3b2o3b3o2b3o3b2o$o3b2o3bo2b2o2bo3b2o3bo2b2o$b3o2b2obo7b3o2b2obo $3bobo2bo10bobo2bo$4bobo13bobo$5bo15bo! [[ GRID THUMBNAIL THEME 6 THUMBSIZE 2 ]]

If this line of three cells is connected to something at the other end, a boat supported by a fishhook works:

x=21, y = 20, rule = LifeHistory 3.A$3.A10.A$3AD9.2D$3A.D8.2AC$4.D10.D$2.A10.A$.A.A8.A.A$2.A10.A3$3.A$ 3.A10.A$3AD9.2D$3A.D8.2AC$4.D10.D$2.A10.A$.A.A2.2A4.A.A2.2A$.2A3.A.A3. 2A3.A.A$8.A10.A$8.2A9.2A! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

If the line is instead four or more cells long, a certain 15-cell catalyst works:

x=18, y = 23, rule = LifeHistory 16.A$16.AD$5.2A9.AD$3.A2.AD9.D$3.3A.D7.2AC$7.D9.D$5.A9.A$4.A.A7.A.A$5. A9.A3$16.A$16.AD$5.2A9.AD$3.A2.AD9.D$3.3A.D7.2AC$7.D9.D$5.A9.A$4.A.A7. A.A$3.A.A7.A.A$.3A.A.A3.3A.A.A$A5.2A2.A5.2A$2A8.2A! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

Sometimes, a tub will have an additional cell on the other side.

x=5, y = 8, rule = LifeHistory A$.A.A$.A.A$.3A$.D$3.A$2.A.A$3.A! [[ GRID THUMBNAIL THUMBSIZE 2 T 3 PAUSE 0.5 ]]

If this happens—even if there are more additional cells—a hexagonal key catalyst can work. There are three variants.

x=111, y = 68, rule = B3/S23 27bo$26bo21bo$25bo18b3ob2o$3bo20bob2o20bo31b2o$4bobo17bo2bo15bo3bo15b o16bo2b2o4bo14bobo$4bobo17bobo17bo2bo16bo2bo16bo19bobo$4b3o17b3o17b3o 17b3o19b3o15b3o2$6bo19bo19bo19bo19bo19bo$5bobo17bobo17bobo17bobo17bob o17bobo$6bo19bo19bo19bo19bo19bo8$27bo$26bo21bo$25bo18b3ob2o$3bo20bob2o 20bo31b2o$4bobo17bo2bo15bo3bo15bo16bo2b2o4bo14bobo$4bobo17bobo17bo2bo 16bo2bo16bo19bobo$4b3o17b3o17b3o17b3o19b3o15b3o2$6bo19bo19bo19bo19bo19b o$3bobobo2bo12bobobo2bo12bobobo2bo12bobobo2bo12bobobo2bo12bobobo2bo$b 3obob4o10b3obob4o10b3obob4o10b3obob4o10b3obob4o10b3obob4o$o5bo13bo5bo 13bo5bo13bo5bo13bo5bo13bo5bo$2o6bo11b2o6bo11b2o6bo11b2o6bo11b2o6bo11b 2o6bo$7b2o18b2o18b2o18b2o18b2o18b2o5$27bo$26bo21bo$25bo18b3ob2o$3bo20b ob2o20bo31b2o$4bobo17bo2bo15bo3bo15bo16bo2b2o4bo14bobo$4bobo17bobo17b o2bo16bo2bo16bo19bobo$4b3o17b3o17b3o17b3o19b3o15b3o2$6bo19bo19bo19bo19b o19bo$2b2obobo2bo11b2obobo2bo11b2obobo2bo11b2obobo2bo11b2obobo2bo11b2o bobo2bo$2b2obob4o11b2obob4o11b2obob4o11b2obob4o11b2obob4o11b2obob4o$5b 2o18b2o18b2o18b2o18b2o18b2o$2b3o3bo13b3o3bo13b3o3bo13b3o3bo13b3o3bo13b 3o3bo$2bo2bob2o13bo2bob2o13bo2bob2o13bo2bob2o13bo2bob2o13bo2bob2o$3b2o 18b2o18b2o18b2o18b2o18b2o4$27bo$26bo21bo$25bo18b3ob2o$3bo20bob2o20bo31b 2o$4bobo17bo2bo15bo3bo15bo16bo2b2o4bo14bobo$4bobo17bobo17bo2bo16bo2bo 16bo19bobo$4b3o17b3o17b3o17b3o19b3o15b3o2$6bo19bo19bo19bo19bo19bo$2b2o bobo2bo11b2obobo2bo11b2obobo2bo11b2obobo2bo11b2obobo2bo11b2obobo2bo$b obobob4o10bobobob4o10bobobob4o10bobobob4o10bobobob4o10bobobob4o$2bo3b o15bo3bo15bo3bo15bo3bo15bo3bo15bo3bo$8bo19bo19bo19bo19bo19bo$7b2o18b2o 18b2o18b2o18b2o18b2o! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

Ship replacements

The ship family is fairly unique as a catalyst family. For most catalyst families, one places the namesake catalyst expecting it to work, and the replacement catalysts are reserves. However, a ship will almost always fail when attempting a ship-type catalysis, and it is much more often the case that one of the replacement catalysts works. However, it is usually worth initially placing lone ships (as opposed to initially placing a replacement catalyst) for three reasons:

1. It takes less time to draw a ship than to draw any of the replacement catalysts;
2. It is easier to see which replacement catalyst, if any, will work by observing a lone ship than by observing any single replacement catalyst;
3. A lone ship will occasionally work. (If a lone ship works, none of the replacement catalysts will work.)

Often, the ship is turned into a loaf, such as in the BLx19R converter. Adding a fishhook turns it back into a ship:

x=72, y = 30, rule = LifeHistory 14.A$16.2A$16.4A9.A.A22.A11.A$.A11.A4.A7.A4.A7.A15.A10.A$2.A.A9.3A10. 3A10.2A11.A.A12.A$3.A12.A12.A12.A12.A12.A$64.A.A$4.2A11.2A11.2A11.2A11. 2A8.A2.2A$4.A.A10.A.A10.A.A10.A.A10.A.A10.A.A$4.D2A10.D2A10.D2A10.D2A 10.D2A10.D2A6$14.A$16.2A$16.4A9.A.A22.A11.A$.A11.A4.A7.A4.A7.A15.A10. A$2.A.A9.3A10.3A10.2A11.A.A12.A$3.A12.A12.A12.A12.A12.A$64.A.A$4.2A11. 2A11.2A11.2A11.2A8.A2.2A$4.A.A10.A.A10.A.A10.A.A10.A.A10.A.A$5.2A11.2A 11.2A11.2A11.2A11.2A2$2.2A11.2A11.2A11.2A11.2A11.2A$3.A12.A12.A12.A12. A12.A$3A10.3A10.3A10.3A10.3A10.3A$A12.A12.A12.A12.A12.A! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

Adding a snake, eater 1 and block will work if clearance is an issue. The snake can be replaced with an eater 1 if it needs to be spartan.

7b2o6bo$8bo4b3o$7bo4bo$7b2o3b2o2$7b2o$6bobo2b2o$3bo2b2o3b2o$4bo$3bo$b2o$o! #C [[ THUMBSIZE 2 THEME 6 GRID GRIDMAJOR 0 SUPPRESS THUMBLAUNCH ]] #C [[ THUMBSIZE 2 GPS 10 ]]

(click above to open LifeViewer)

If the loaf parent has an extra cell in a certain position (so that it becomes a great-uncle of the I-heptomino), there's another replacement catalyst that works (which was discovered fairly recently to use in the R49 conduit, so it is often called the "R49 catalyst"):

x=14, y = 29, rule = LifeHistory 3.A$4.2A2$4.A.A$5.A2$5.D2A$6.A.A$6.D2A7$3.A$4.2A2$4.A.A$5.A2$6.2A$3.A .A2.A$.3A.A.2A$A4.A$.3A.A4.2A$3.2A5.A$11.3A$13.A! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

It can work even if the chaos doesn't leave the ship/I-relative.

x=74, y = 28, rule = LifeHistory 4.A59.A$4.A2.A18.A39.2A$4.A.A17.A.A17.A.A16.2A$5.A19.A19.A19.A2$5.D2A 17.D2A17.D2A17.D2A$6.A.A17.A.A17.A.A17.A.A$6.D2A17.D2A17.D2A17.D2A8$4. A59.A$4.A2.A18.A39.2A$4.A.A17.A.A17.A.A16.2A$5.A19.A19.A19.A2$6.2A18. 2A18.2A18.2A$3.A.A2.A14.A.A2.A14.A.A2.A14.A.A2.A$.3A.A.2A12.3A.A.2A12. 3A.A.2A12.3A.A.2A$A4.A14.A4.A14.A4.A14.A4.A$.3A.A4.2A9.3A.A4.2A9.3A.A 4.2A9.3A.A4.2A$3.2A5.A12.2A5.A12.2A5.A12.2A5.A$11.3A17.3A17.3A17.3A$13. A19.A19.A19.A! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

When considering replacing the ship with an R49 catalyst, it is very important that the marked cell has three live neighbors on generation two.

x=5, y = 7, rule = LifeHistory 2.A$A.A$.A$3.D$2.2A$2.A.A$3.2A! [[ GRID THUMBNAIL THUMBSIZE 2 T 2 PAUSE 0.5 ]]

If the marked cell only has two live neighbors on generation two, don't bother placing an R49 catalyst; it won't work.

x=54, y = 27, rule = LifeHistory 4.A42.A$4.A.A16.2A19.A.A$5.A19.A19.A$7.D19.D19.D$6.2A18.2A18.2A$6.A.A 17.A.A17.A.A$7.2A18.2A18.2A9$4.A42.A$4.A.A16.2A19.A.A$5.A19.A19.A2$6. 2A18.2A18.2A$3.A.A2.A14.A.A2.A14.A.A2.A$.3A.A.2A12.3A.A.2A12.3A.A.2A$ A4.A14.A4.A14.A4.A$.3A.A4.2A9.3A.A4.2A9.3A.A4.2A$3.2A5.A12.2A5.A12.2A 5.A$11.3A17.3A17.3A$13.A19.A19.A! [[ GRID THUMBNAIL THUMBSIZE 2 T 2 PAUSE 0.5 ]]

In situations where that cell only has two live neighbors, an Sparking eater sometimes works.

x=49, y = 29, rule = LifeHistory 2.3A18.2A$21.2A16.2A4.2A$.A42.A$.A.A16.2A19.A.A$2.A19.A19.A$4.D19.D19. D$3.2A18.2A18.2A$3.A.A17.A.A17.A.A$4.2A18.2A18.2A7$2.3A18.2A$21.2A16. 2A4.2A$.A42.A$.A.A16.2A19.A.A$2.A19.A19.A2$3.2A2.2A14.2A2.2A14.2A2.2A $A3.A2.2A11.A3.A2.2A11.A3.A2.2A$4A16.4A16.4A2$2A20.2A16.2A$2A20.2A16. A$38.A.A$38.2A! [[ GRID THUMBNAIL THUMBSIZE 2 T 2 PAUSE 0.5 ]]

However, it is sensitive to the chaos not clearing.

x=49, y = 27, rule = B3/S23 bo42bo$bobo16b2o19bobo$2bo19bo19bo2$3b2o18b2o18b2o$3bobo17bobo17bobo$ 4b2o18b2o18b2o9$bo42bo$bobo16b2o19bobo$2bo19bo19bo2$3b2o2b2o14b2o2b2o 14b2o2b2o$o3bo2b2o11bo3bo2b2o11bo3bo2b2o$4o16b4o16b4o2$2o20b2o16b2o$2o 20b2o16bo$38bobo$38b2o! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

If the R49 catalyst functions properly, but the active reaction interferes (either at the same time or at a different time) with the side opposite the fishhook, a different catalyst consisting of a transparent loaf and a large block replacement catalyst may work instead. Note that the red cell must not be born in generation three for the secondary replacement catalyst to work.

x=19, y = 30, rule = LifeHistory 5.2A$4.A$4.A.A$4.A.A$4.DA2$6.2A$3.A.A2.A$.3A.A.2A$A4.A$.3A.A4.2A$3.2A 5.A$11.3A$13.A3$5.2A$4.A9.2A$4.A.A6.A.A$4.A.A6.A$4.DA6.2A.A$11.A3.3A$ 6.2A3.2A.A3.A$5.A2.A6.A.A$5.A.A3.5A.2A$6.A4.A4.A$12.3A.A$14.A.2A$14.A $13.2A! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

A fishhook bridge fishhook works when the ship turns into a certain blockade predecessor.

x=68, y = 31, rule = LifeHistory .A38.A22.A$.A20.A17.A2.A19.A$2.A19.A16.A.A2.A16.A$.A17.2A.A18.A2.A16. A$.A19.A19.A19.A2$.DAC17.DAC17.DAC17.DAC$.DC.C16.DC.C16.DC.C16.DC.C$2. D2C17.D2C17.D2C17.D2C12$.A38.A22.A$.A20.A17.A2.A19.A$2.A19.A16.A.A2.A 16.A$.A17.2A.A18.A2.A16.A$.A19.A19.A19.A2$2.2A18.2A18.2A18.2A$2.A.A17. A.A17.A.A17.A.A$A.A.3A13.A.A.3A13.A.A.3A13.A.A.3A$2A5.A12.2A5.A12.2A5. A12.2A5.A$6.2A18.2A18.2A18.2A! [[ GRID THUMBNAIL THUMBSIZE 2 T 4 PAUSE 1 ]]

Lone ships, ship-fishhook pairs, and R49 catalysts are more likely to work when the cell that "activates" them survives into the next generation, while a fishhook bridge fishhook catalyst is more likely to work if by the next generation, the cell that "activated" it has died, and it has a two-cell edge to "slam" into. Common examples of the latter are a grin (like in 30P6.1) and a certain edgeshootable beehive predecessor.

x=18, y = 11, rule = LifeHistory 11.A$.A9.A$2.A9.A$2.A8.A$.C9.C2$2.2A8.2A$2.A.A7.A.A$A.A.3A3.A.A.3A$2A 5.A2.2A5.A$6.2A8.2A! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

While this is a trend, this is not a hard-and-fast rule. Here are demonstrations of this (mostly from earlier in this section):

x=65, y = 13, rule = LifeHistory 8.A19.A14.A15.A$A5.2A6.A14.A15.2A12.A$.A.2A10.2A10.A.A12.2A12.2A.A$.A 3.C11.C11.C14.C13.C2$6.2A10.2A10.2A13.2A12.2A$6.A.A9.A.A9.A.A9.A.A2.A 11.A.A$7.2A10.2A10.2A7.3A.A.2A9.A.A.3A$39.A4.A12.2A5.A$16.2A10.2A10.3A .A4.2A12.2A$17.A11.A12.2A5.A$14.3A9.3A21.3A$14.A11.A25.A! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

For this reason, as well as the fact that a ship takes less time to draw than a fishhook bridge fishhook (and you can still tell whether or not a fishhook bridge fishhook will work by observing a ship), It is best to place a lone ship instead of a fishhook bridge fishhook even in situations that look like a fishhook bridge fishhook is the most likely ship-type catalyst to work.

Occassionally, instead of simply becoming the aforementioned blockade predecessor, the ship will become that blockade predecessor with three additional cells, and if one uses a fishhook bridge fishhook, it will mostly recover but with three extra cells in the same position. When this happens, a beehive works.

x=149, y = 44, rule = LifeHistory 104.A$62.A41.2A$2A2.A13.A44.2A34.A21.2A4.A14.2A.A$.A2.A14.2A18.A.A.A15. A17.A5.A16.A2.A16.A3.3A16.3A$2.A2.A15.2A15.2A.2A17.2A.A15.2A2.A15.A2. A20.A18.A$2.A2D17.A2D13.A3.A2D17.A2D14.A2.A2D13.A3.A2D17.A2D17.A2D$4. D19.D19.D19.D19.D19.D19.D19.D$2.DAC17.DAC17.DAC17.DAC17.DAC17.DAC17.D AC17.DAC$2.DC.C16.DC.C16.DC.C16.DC.C16.DC.C16.DC.C16.DC.C16.DC.C$3.D2C 17.D2C17.D2C17.D2C17.D2C17.D2C17.D2C17.D2C8$104.A$62.A41.2A$2A2.A13.A 44.2A34.A21.2A4.A14.2A.A$.A2.A14.2A18.A.A.A15.A17.A5.A16.A2.A16.A3.3A 16.3A$2.A2.A15.2A15.2A.2A17.2A.A15.2A2.A15.A2.A20.A18.A$2.A2D17.A2D13. A3.A2D17.A2D14.A2.A2D13.A3.A2D17.A2D17.A2D$4.D19.D19.D19.D19.D19.D19. D19.D$3.2A18.2A18.2A18.2A18.2A18.2A18.2A18.2A$3.A.A17.A.A17.A.A17.A.A 17.A.A17.A.A17.A.A17.A.A$.A.A.3A13.A.A.3A13.A.A.3A13.A.A.3A13.A.A.3A13. A.A.3A13.A.A.3A13.A.A.3A$.2A5.A12.2A5.A12.2A5.A12.2A5.A12.2A5.A12.2A5. A12.2A5.A12.2A5.A$7.2A18.2A18.2A18.2A18.2A18.2A18.2A18.2A6$104.A$62.A 41.2A$2A2.A13.A44.2A34.A21.2A4.A14.2A.A$.A2.A14.2A18.A.A.A15.A17.A5.A 16.A2.A16.A3.3A16.3A$2.A2.A15.2A15.2A.2A17.2A.A15.2A2.A15.A2.A20.A18. A$2.A19.A15.A3.A19.A16.A2.A15.A3.A19.A19.A2$3.2A18.2A18.2A18.2A18.2A18. 2A18.2A18.2A$2.A2.A16.A2.A16.A2.A16.A2.A16.A2.A16.A2.A16.A2.A16.A2.A$ 3.2A18.2A18.2A18.2A18.2A18.2A18.2A18.2A! [[ GRID THUMBNAIL THUMBSIZE 2 T 4 PAUSE 1 ]]

Sometimes the ship will be converted to a butterfly. If that happens, a period-multiplying half-bakery/ship-tie catalyst can restore it. This reaction works when there is a line of three or more diagonal cells that all formed in the same generation. This catalyst was found via semi-natural soup search. Note that this is unique in the fact that there is no non-period multiplying version known.

x=71, y = 55, rule = LifeHistory 39.A17.A$11.3A23.A2.A14.A2.A$10.3ABA22.A3.A13.A3.A$9.A3B2A21.A4.A12.A 4.A$9.AB3AD21.A4.C12.A4.C$10.3AD26.C17.C$11.AD24.2AC2.2A11.2AC2.2A$ 41.A.A15.A.A3.A$41.2A4.2A10.2A3.A.A$46.A.A14.A2.A$46.2A14.A.2A$44.2A 15.A.A$43.A.A14.A2.A$43.2A16.2A12$12.A23.3A19.3A$11.3A21.A3.A17.A3.A$ 10.5A19.A5.A15.A5.A$9.2A3.2A17.A3.A3.A13.A3.A3.A$8.3A3.3A16.A2.A.A2.A 13.A2.A.A2.A$9.2A3.2AD16.A3.A3.C13.A3.A3.C$10.5AD18.A5.C15.A5.C$11.3A D20.A3.C2.2A13.A3.C2.2A$12.A23.3A2.A.A14.3A2.A.A3.A$41.2A4.2A14.2A3.A .A$34.2A10.A.A7.2A9.A2.A$35.A10.2A9.A8.A.2A$32.3A9.2A8.3A8.A.A$32.A 10.A.A8.A9.A2.A$43.2A20.2A10$22.A$D3.D7.3A6.A.A$.D.D8.A.AD4.A3.C$2.D 9.2AC6.A.C$.D.D9.D8.C$D3.D! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

Bonus catalyses

Here are some extra catalyses which might come in useful. This section is optional as the catalysts used are fairly rare.

Eater 3

You might notice that when you hit a loaf with a glider in a certain way, the loaf flips around:

x=15, y = 14, rule = B3/S23 2bo$obo$b2o$5b2o$4bo2bo$4bobo$5bo5$12b3o$12bo$13bo! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

This is quite inconvenient for us because we can't use the loaf again (unless we flip it back around with another glider as shown in the viewer, which is unlikely), but a stable catalyst does exist to turn the loaf back around. Here is the eater 3:

x=16, y = 15, rule = b3s23 2bo$obo$b2o$5b2o$4bo2bo2b2o$4bobo4bo2bo$5bo5bobobo$8b2obo2bo$8bo2bo$5b o4bo$5b5o2$7bo$6bobo$7bo! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

The eater 3 will work with objects that have either the three yellow cells or six green cells turned on. The catalysis involving the yellow cells very rarely fails if the chaos clears quickly.

x=15, y = 15, rule = LifeHistory 10.C.C$11.CE$12.2EC$9.2A2.C$4.2A2.A2.A2.C$.A2.A4.A.A$A.A.A5.A$.A2.A.2A $4.A2.A$5.A4.A$6.5A2$8.A$7.A.A$8.A! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

However, it is sensetive to the chaos not clearing. Most of the time, when eater 3 fails, it transforms to a related still life.

x=17, y = 17, rule = LifeHistory $12.A$12.A.A$12.2A$12.4A$9.2A$4.2A2.A2.A$.A2.A4.A.A$A.A.A5.A$.A2.A.2A $4.A2.A$5.A4.A$6.5A2$8.A$7.A.A$8.A! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

The eater 3 has some other applications besides eating gliders, for example the rectifier. Typically the eater 3 is used when a fishhook fails on a corner (in at least one orientation), and there aren't any replacement catalysts that work.

x=35, y = 14, rule = B3/S23 2bo19bo$3o17b3o$4b2o18b2o$4bobo16bo2bo2b2o$6bo16bobo4bo2bo$6b2o16bo5b obobo$27b2obo2bo$27bo2bo$24bo4bo$24b5o2$26bo$25bobo$26bo! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

There is also a drifty variant of the eater 3 that catalyzes in the same way, but recovers differently (shown as the example catalyst at the top of this page). While it has a lower population and bounding box, it has a much lower side clearance:

x=11, y = 10, rule = b3s23 o$b2o$2o7b2o$4b2obo2bo$3bobob3o$3bobo$b3ob5o$o3bo4bo$2o2bobo$5b2o! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

The drifty variant of the Eater 3 also comes with a variant that produces a thumb spark, in case a spark is needed and sparking eater fails.

x=22, y = 18, rule = B3/S23 bo$2bo$3o3$6bo$7bo$5b3o3$16b2o$11b2obo2bo2bo$10bobob2obobobo$7bo2bobo 4bo2bo$7b4ob4obo$11bo4bo$9bobo2bo$9b2o3b2o! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

Also, there is an alternative way to restore the loaf's orientation that is sometimes useful for welding purposes.

x=22, y = 19, rule = B3/S23 20b2o$20b2o4$15b2obo$15b2ob3o$3o7b2o9bo$bo7bo2bo2b2ob3o$b3o5bobo4bobo $10bo5bo$13b2obo$11bo2bob2o$7b2o2b3o$7bo$8b6o$13bo$10bobo$10b2o! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

Eater 3 Replacements

Sometimes, the chaos does not clear up during the reaction. In that case, Moose antlers might work. However, it relies on a domino spark to restore it, so it is not guarenteed to work, and in fact will rarely work.

x=34, y = 15, rule = B3/S23 25bo$24bobo$25bo2$23b5o$4bo18bo4bo$3bobo4b2o14bo2bo$4bo4bobo14b2obo2b o$9bo13bo5bobobo$7b3o12bobo4bo2bo$b2o3bo10b2o3bo2bo2b2o$2bo4b3o8bo4b2o $5o4bo6b5o$o3b2o3bobo4bo3b2o$10b2o! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

Loaf

Besides its usage in the eater 3, the loaf has a pseudo-transparent catalysis that can eat a certain beehive predecessor (taken from a variant of RF28B, for example) or two block predecessors that are similar to each other.

x=32, y = 7, rule = B3/S23 o23bo$24bo$b3o8bob2o9b3o$5bo7bo3bo11bo$4bobo9bobo9bobo$4bo2bo8bo2bo8b o2bo$5b2o10b2o10b2o! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

This type of loaf catalysis is used in Kazyan's method of restoring a block that has been turned into a beehive while generating a Herschel.

x=15, y = 18, rule = B3/S23 obo$b2o$bo8$8b2o$7bo2bo$8b2o2$12bo$11bobo$11bo2bo$12b2o! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

Hook with tail

The hook with tail can serve as a rock:

x=54, y = 13, rule = B3/S23 43b2o2$26bo18bo$26bo16bo2bo4b2o$27bo2bo12bo2bo4bobo$27b3o14b3o5bo$b2o b2o4b3o4b5o12bob3o$3bo7bo8bo14bo2$2bobo5bobo6bobo5bobo5bobo6bobo$bob2o 4bob2o5bob2o4bob2o4bob2o5bob2o$bo7bo8bo7bo7bo8bo$2o6b2o7b2o6b2o6b2o7b 2o! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

It does not care about orientation.

x=37, y = 13, rule = B3/S23 26b2o2$9bo18bo$9bo16bo2bo4b2o$10bo2bo12bo2bo4bobo$10b3o14b3o5bo$5o12b ob3o$3bo14bo2$2bobo5bobo5bobo6bobo$2b2obo4b2obo4b2obo5b2obo$5bo7bo7bo 8bo$5b2o6b2o6b2o7b2o! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

Hook with tail replacements

Sometimes, hook with tail will fail in a certain way:

x=35, y = 18, rule = B3/S23 4$7bo$7b3o$10bo$9bo7b3o$9b2o6bobo$17bobo! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 STOP 17 ]]

In that case, it can be replaced with this catalyst:

x=33, y = 24, rule = B3/S23 6$18b2o$18bo$15b2obo$13bo2bob2o$13b2obo$16bo$16b2o$24b3o$16b2o6bobo$16bo7bobo$14bobo$14b2o! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

And catalysis of longer hook with tail.

x=10, y = 52, rule = LifeHistory 3.C$2.3C$3.C$2.E.E$.A.2E$.A$2A4$4.2C$4.2C$2.E.C$.A.E.E$.A2.2E$2A5$4.C $4.3C$2.E.3C$.A.E.C$.A2.E.E$2A3.2E6$5.C$5.2C$3.E.4C$2.A.E.3C$2.A2.E.C $.2A3.E.E$7.2E7$5.C$5.2C$3.E.3C$2.A.E.4C$2.A2.E.3C$.2A3.E.C$7.E.E$8.2E ! [[ GRID THUMBNAIL THUMBSIZE 2 ]]

Eater 4

The eater 4 primarily catalyses symmetrical objects. Its most common use is to catalyze a honey farm:

x=44, y = 15, rule = B3/S23 b2o$o2bo5b2o20b2o6b2o$3o7bo19bo2bo6bo$10bob2o16b3o7bob2o$9b2o2bo11bo13b 2o2bo$6bo4b2o12bo10bo4b2o$6b5o14bo10b5o$4b2o4bo23b2o4bo$5bo2b2o25bo2b 2o$5bobo27bobo$o2bobobo22bo2bobobo$4ob2o23b4ob2o$4bo29bo$2bobo27bobo$ 2b2o28b2o! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

This can also come in handy sometimes; for example the recently-discovered L122 conduit.

In order for the eater 4 to recover, it needs to stay diagonally symmetric. If there is a line of two on each side, it will receive dot sparks on both sides, stay symmetric, and recover properly.

x=74, y = 14, rule = B3/S23 3bo5b2o21bo6b2o28b2o$3bo6bo20bo8bo22bo6bo$2bobo5bob2o16bo2b2o5bob2o17b o2bo5bob2o$2o2bo4b2o2bo18bobo4b2o2bo17bo2bo4b2o2bo$2b2o2bo4b2o19b2o2b o4b2o20bo2bo4b2o$6b5o25b5o21bo3b5o$4b2o4bo23b2o4bo23b2o4bo$5bo2b2o25b o2b2o25bo2b2o$5bobo27bobo27bobo$o2bobobo22bo2bobobo22bo2bobobo$4ob2o23b 4ob2o23b4ob2o$4bo29bo29bo$2bobo27bobo27bobo$2b2o28b2o28b2o! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

If there is a line of three or more on each side, it will receive a dot spark on neither side, stay symmetric, and recover properly.

x=134, y = 14, rule = B3/S23 9b2o20b3o5b2o23bo4b2o22b2o4b2o28b2o$4bo5bo19bo3bo5bo23bo5bo23bo5bo23b o5bo$4bo5bob2o16bo3bo5bob2o20bo5bob2o20bo5bob2o20bo5bob2o$4bo4b2o2bo16b o3bo4b2o2bo20bo4b2o2bo20bo4b2o2bo20bo4b2o2bo$b3o2bo4b2o18b3o2bo4b2o17b 4o2bo4b2o18b3o2bo4b2o19b2o2bo4b2o$6b5o25b5o25b5o25b5o20bo4b5o$4b2o4bo 23b2o4bo23b2o4bo23b2o4bo23b2o4bo$5bo2b2o25bo2b2o25bo2b2o25bo2b2o25bo2b 2o$5bobo27bobo27bobo27bobo27bobo$o2bobobo22bo2bobobo22bo2bobobo22bo2b obobo22bo2bobobo$4ob2o23b4ob2o23b4ob2o23b4ob2o23b4ob2o$4bo29bo29bo29b o29bo$2bobo27bobo27bobo27bobo27bobo$2b2o28b2o28b2o28b2o28b2o! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

However, if there is a line of two on one side and a line of three or more on the other side, it will receive a dot spark on one side but not the other, so it will lose its symmetry and fail.

x=74, y = 15, rule = B3/S23 63bo$9b2o28b2o23bo4b2o$4bo5bo22bo6bo23bo5bo$4bo5bob2o19b2o5bob2o17bo2b o5bob2o$2o2bo4b2o2bo20bo4b2o2bo17bo2bo4b2o2bo$2b2o2bo4b2o18b3o2bo4b2o 19b2o2bo4b2o$6b5o25b5o25b5o$4b2o4bo23b2o4bo23b2o4bo$5bo2b2o25bo2b2o25b o2b2o$5bobo27bobo27bobo$o2bobobo22bo2bobobo22bo2bobobo$4ob2o23b4ob2o23b 4ob2o$4bo29bo29bo$2bobo27bobo27bobo$2b2o28b2o28b2o! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

Even if the interaction lasts unusually long, as long as the eater 4 maintains its symmetry, it still has a chance of recovering.

x=14, y = 14, rule = B3/S23 9b2o$2bo7bo$b2o7bob2o$3bo5b2o2bo$6bo4b2o$6b5o$4b2o4bo$5bo2b2o$5bobo$o 2bobobo$4ob2o$4bo$2bobo$2b2o! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

Eater 4 replacements

Sometimes, the Eater 4 needs to be replaced with a similar catalyst which does the same thing but might have better side clearance. There is a variant specially for that:

x=15, y = 15, rule = B3/S23 2bo$bobo$obobo$o3bo$b3ob2o$3bobobo$5bobo$5bo2b2o$4b2o4bo$6b5o$6bo4b2o $9b2o2bo$10bobobo$10bo2bo$11b2o! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

Alternatively, if the Eater 4 is used to eat a half of a traffic light, a transparent ship can be used to substitute, at the cost of a higher recovery time.

x=7, y = 6, rule = B3/S23 b2o$obo$2o2$5bo$4b3o! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

This may seem pretty niche, but it is actually a fairly common application, for example in p32 blinker hassler 2.

Beehive push catalyst

Observe the following reaction:

x=3, y = 10, rule = B3/S23 bo$obo$obo$bo4$3o$obo$obo! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

The beehive doesn't get destroyed by the pi-heptomino, but shifted or "pushed" one cell. This "push" can be reversed with the beehive push catalyst:

x=17, y = 18, rule = B3/S23 6b2ob2o$7bobo$2b2obo5bob2o$bobob2o3b2obobo$o6bobo6bo$7o3b7o2$2b3o7b3o $bo2bo3bo3bo2bo$b2o4bobo4b2o$7bobo$8bo4$7b3o$7bobo$7bobo! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

Note that the marked cell has to be alive in generation 6 but not generation 5 or the catalyst will fail.

x=17, y = 19, rule = LifeHistory 6.2A.2A$7.A.A$2.2A.A5.A.2A$.A.A.2A3.2A.A.A$A6.A.A6.A$7A3.7A2$2.3A7.3A $.A2.A3.A3.A2.A$.2A4.A.A4.2A$7.ADA$8.A2$7.3A$6.A2.A$6.A3.A$5.2A.A.A$5. 2A.2A$6.3A! [[ GRID THUMBNAIL THUMBSIZE 2 GPS 4 STOP 5 ]]

Beehive push catalyst replacements

Sometimes the beehive will be destroyed. If it is converted into a traffic light when the leading edge is one cell off-center, this variant will work.

x=21, y = 26, rule = B3/S23 8b2ob2o$9bobo$4b2obo5bob2o$3bobob2o3b2obobo$2bo6bobo6bo$3b6o3b6o$3o15b 3o$o3b3o7b3o3bo$b3o2bo3bo3bo2b3o$4bo4bobo4bo$3bo5bobo5bo$3bobo4bo4bob o$4bobo7bobo$5bo9bo$10bo$9bobo$9bobo$10bo6$8bo$7b3o$9bo! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

Sometimes a beehive will become a honey farm predecessor.

x=17, y = 19, rule = B3/S23 6b2ob2o$7bobo$2b2obo5bob2o$bobob2o3b2obobo$o6bobo6bo$7o3b7o2$2b3o7b3o $bo2bo3bo3bo2bo$b2o4bobo4b2o$7bobo$8bo2$7b3o$6bo3bo2$5bo$5bo$5b2o! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

In that case, this catalyst can be used:

x=11, y = 15, rule = B3/S23 2b2o$2b2o2$4o$o3bo$3bobob2obo$3bobobob2o$4bo2$3b3o$2bo3bo2$bo$bo$b2o! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

Alternatively, if clearance permits, Snark64 can be used to release an additional glider.

x=27, y = 24, rule = B3/S23 5bo$5b3o$8bo$7b2o15b2o$23bobo$3b2o14b2o2bo$2bo2bo13bobob2o$2bob2o14b2o bo2bo$b2o22b2o$o3b2o$b3o2bo$4b2obo15b2o$3bo2bo5bo10b2o$3b2o6bobo$11bo bo$12bo$22b2o$11b3o9bo$10bo3bo5b3o$20bo$11b3o7b2o$22bo$21bo$21b2o! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

If the beehive is pushed twice but is otherwise undamaged, this replacement catalyst works.

x=17, y = 17, rule = B3/S23 4bo3bo3bo$3bobobobobobo$2bo2bobobobo2bo$2b3o2bobo2b3o$7bobo$2b5o3b5o$ bo13bo$2b3o7b3o$4bo7bo$2b2o4bo4b2o$2bo4bobo4bo$obo4bobo4bobo$2o6bo6b2o 2$7b3o$6b4o$6bo3bo! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

The double beehive push catalyst can also work as a 2c/3 wire injector. This application has been used to create injectors with the lowest repeat times, the fastest theoretically having a repeat time of 29.

x=20, y = 21, rule = B3/S23 2ob2o$bobobob2o$o2bobobo$3o2bobo$5bobob2o3bo$5o2bobobobobo$o6bobobobo 2bo$b6o2bobo2b3o$9bobo$3b6o3b5o$3bo13bo$4b3o7b3o$6bo7bo$4b2o4bo4b2o$4b o4bobo4bo$b2obo4bobo4bob2o$bobo6bo6bobo2$9b3o$9b4o$8bo3bo! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

Tub-with-tail eater (eater 5)

The tub-with-tail eater can catalyse from multiple directions, as well as having a high clearance. A single protruding cell of the tub (or boat or loaf, depending on the variant) is temporarily turned off, and then is restored by interaction with surrounding catalyst cells. With the variants using a boat, the boat temporarily turns into a wing.

x=12, y = 14, rule = B3/S23 o$b2o$2o2$6bo$6bobo$6b2o2$10b2o$6bo3b2o$5bobo$4bobo$4bo$3b2o! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ]]

Tub-with-tail eater replacements

Sometimes, the tub-with-tail eater needs to be replaced with a similar catalyst which does the same thing but might have better clearance relative to the active region. There are variants specially for that:

This catalyst is one cell further from the active region, using the long hook with tail instead of a block.

x=13, y = 15, rule = B3/S23 o$b2o$2o2$6bo$6bobo$6b2o3$6bo3b2o$5bobo3bo$4bobo3bo$4bo4bo$3b2o5b3o$ 12bo! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ZOOM 12 ]]

The 7 × 9 eater is one cell further from the active region and 2 cells narrower.

x=12, y = 18, rule = B3/S23 o$b2o$2o2$6bo$6bobo$6b2o3$6bo3b2o$5bobo3bo$5b2o3bo$9bo$5b5obo$5bo4b2o$ 6b3o$8bob2o$9bobo! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ZOOM 12 ]]

This catalyst is equivalent to a tub with tail eater in situations where severe lack of clearance doesn't allow any of the smaller forms.

x=13, y = 18, rule = B3/S23 4bo2bo$4b4o$2b2o4b2o$2bo2b2o3bo$4b2ob3o$7bo$4b3o$4bo$9b2o$9bobo$3b3o5b o$3bobo5b2o$b2o2bo$bo3$b2o$o2bo! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ZOOM 12 ]]

The sidesnagger can be used if it is required to be spartan, or if the active region interferes with both the block and long hook with tail. Notice the significantly longer recovery time, and also the slightly reduced clearance: a glider that's traveling in the same direction as the SW-traveling input glider in the example below, has to be at least three half diagonals northwest of the input lane. Other eater 5 variants need only two half diagonals of clearance.

x=16, y = 20, rule = B3/S23 obo$b2o$bo4$9bo$9bobo$9b2o3$9bo$8bobo$7bo2bo3b2o$8b2o4b2o$4bo$3bobo$3b 2o$9b2o$9b2o! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 ZOOM 12 ]]

Bi-boat

Sometimes, an active reaction will have this frontend:

x=5, y = 3, rule = B3/S23 3b2o$2ob2o$2bo! [[ GRID THEME 6 THUMBNAIL THUMBSIZE 2 VIEWONLY ]]

When that happens, a bi-boat might be able to catalyze the reaction if it is placed two generations earlier.

x=49, y = 22, rule = LifeHistory 2.A14.A12.3A$2.A12.A.A11.A14.2A$2.A.A9.A3.A9.A5.A9.A.A$2.A.CD10.A.CD10. 2ACD10.A.CD$.DCACD9.DCACD9.DCACD9.DCACD$3.D13.D13.D13.D8$2.A14.A12.3A $2.A12.A.A11.A14.2A$2.A.A9.A3.A9.A5.A9.A.A$2.A.A11.A.A11.3A11.A.A$2.3A 11.3A11.3A11.3A2$.A3.A9.A3.A9.A3.A9.A3.A$A.A.A.A7.A.A.A.A7.A.A.A.A7.A .A.A.A$.2A.2A9.2A.2A9.2A.2A9.2A.2A! [[ GRID THUMBNAIL THUMBSIZE 2 GPS 10 T 2 PAUSE 0.8 T 7 PAUSE 5 GPS 1 ]]

Finding new catalysts

Mike Playle's Bellman is a search program specifically designed to search for new catalysts, given a reaction to be perturbed. It discovered the Snark, as well as many other highly notable patterns. This part of the tutorial hasn't been written yet, so consult the discussion thread and original documentation.

Another catalyst finding program is CatForce, which is a brute force placement program of certain given catalysts in a given area, and can also find transparent catalysts if they're restored quickly enough. It has also discovered quite a few interesting things, like B60, 58P37, and the p84 honey farm hassler.

External links

• The Hunting of the New Herschel Conduits (discussion thread) at the ConwayLife.com forums
• The Hunting of the Elementary Conduits (discussion thread) at the ConwayLife.com forums
• Catalyst Discussion Thread (discussion thread) at the ConwayLife.com forums
• Thread for your unusual catalyses (discussion thread) at the ConwayLife.com forums
• Eater Welding Guide (discussion thread) at the ConwayLife.com forums