Board Thread:General Discussion/@comment-3967802-20131024044838

I've been assuming that the Crimson spreads the same way as the Corruption and the Hallow, but I haven't done any real testing on it. I can't seem to keep my Crimson and Hallow contained, and I don't know why.

Some questions (for Hard Mode):

1. Which blocks can be converted to the Crimson/the Hallow/the Corruption?

2. Which blocks cannot be converted?

3. Which blocks spread the Crimson/Hallow/Corruption?

4. Can the Crimson spread across walls?

5. How many empty blocks are necessary to contain the Crimson?

6. Is there a way to revert the Jungle after it has been corrupted?

Background:

After 1.2 was released, I created a new world for my existing character to play in. Before I defeated the Wall of Flesh, I spent quite a bit of time creating a bunch of firewalls to contain the Crimson and the Hallow. I made a firewall around each section of surface crimson. I made two H-shaped firewalls on either side of my house, and a firewall next to each of my oceans. I'd read that the Corruption couldn't spread to the Jungle or the Dungeon, so I left those alone. Each firewall was a 3-block wide hellevator, going from the surface to the Underworld. I left the walls as-is. I didn't bother replacing the blocks on the side because I thought the empty space would be enough.

Then I beat the Wall of Flesh and smashed 4-5 demon alters to give my world the new ore. When I found surface Hallow, I created new firewalls. Slowly, I noticed that my Underworld was being converted into Crimson Underground and Hallow Underground. I also found that the Hallow had spread (very slightly) across one of my firewalls. :-( I guessed that the crystals that grow in the Underground Hallow might count as a block, so I expanded all of my firewalls to 4 blocks.

Here's how I think some of this works in Hard Mode.

The Crimson, The Hallow, and The Corruption all work basically the same way. (So, for the rest of this, I'm just going to refer to the corruption).

1. The Corruption can spread through dirt, particularly if there's grass on it. The corruption also changes mud to dirt, sand to Ebonsand, stone to Ebonstone, and probably ash to Ebonstone. I think it can also use the stone stalagmites, hanging grass, stone moss, and crystals to spread.

2. The Corruption cannot spread through placed, normal wood (although it can spread through trees). It can't spread through clay either. I don't know if it can spread through any of the bricks. I don't think it can spread through Dungeon Bricks. I doubt it can spread through asphalt, and I have no idea about the honey combs. I also don't know if it can spread through water.

3. Ebonstone, Ebonsand, and dirt with Corrupt Seeds/Grass will spread the corruption. I don't think that Demonite spreads the corruption. I don't know if placed Ebonwood spreads the corruption.

4. I think that the corruption can spread through removable-walls (even those placed at world creation). I can't come up with any other reason why the corruption seems to spread through big continous blocks. Or why there are some crimson colored walls after I've sprayed the crimson with green solution using the Clentaminator.

5. I have no idea. I don't think it could spread across a column of 6 empty blocks with no walls, but I'm just guessing. Vile Spit doesn't spread the corruption anymore, so I don't think there's anything that would corrupt a totally segragated, pure set of blocks of stone, etc.

6. I think the only way to get your Jungle Biome back is to purify the Corruption, then replace all the dirt with mud, then plant Jungle Seeds and let it grow. Yuck. It seems like all the other biomes can be fixed using the Clentaminator, which is weird.

Any help or ideas would be greatly appreciated. 