So as long as I dig around my base, the crimson/hallow wont get me?

[H. P. Hatecraft]

So like if I cut a section of land and quarantine it will it stay clean?

[76561198141982149]

corruption/crimson and hallow won't spread from one block to another if the distance between the blocks is 3 tiles or more. So, if you dig a 3 blocks thick vertical shaft all the way from the surface to the underworld, each side of the shaft will be isolated from the other. If you just want to isolate a small area then surround it with a 3 blocks wide tunnel, then fill it with uncorruptible blocks, like bricks(because i believe vines can spread the biomes too)
That said, when you destroy an altar, a patch of crimson or hallow will spawn in a random location of the map.

[Ferfelende Shako]

What also should be noted: If you have corruption in your world watch out for the corruptors, if their spit manages to hit your land, it WILL turn into corruption, you can easily clean this little patch of corruption with purification powder or other means. If you made your land of uncorruptable blocks you have nothing to worry about in the first place

[H. P. Hatecraft]

I just had to fight back a random crimson infestation in my caverns below my base. Just got done cutting 3 tile wide shafts around it all.

[Ferfelende Shako]

You should be fine then, your world does not contain corruption and before hardmode sunflowers placed on surface grass will stop corruption/crimson from spreading past them, when hardmode is enabled however... I would suggest using a little thing called the Clentaminator.

[H. P. Hatecraft]

Also, does crimson take over snow biomes or the dungeon? My desert is between a snow biome and dungeon is it safe?

[ShadeDaystar]

Originally posted by Stout Shako:

watch out for the corruptors, if their spit manages to hit your land, it WILL turn into corruption

As of patch 1.2, corruptors no longer spread corruption.

Snow blocks and dungeon blocks are uncorruptable. However, Ice blocks ARE corruptable. Most of the blocks in the game don't spread biomes, in one way or another. I believe it's so people will have as many options as possible, with as few limitations as possible. This could also be why Clowns no longer destroy bricks (though goblins do still break down doors).

Having a break around your town can limit corruption spread, but smashing alters has a chance of turning a random stone block into ebonstone, crimstone, or pearlstone; which could spread corruption if it happens to take place inside your quarentine. Just keep an eye out for stuff like that.

[Ferfelende Shako]

Hmmm, well there is a lot to tell about this subject, I'll try to keep it as compact as possible.

Crimson/Corruption BEFORE hardmode will only spread across dirt blocks with grass on them, so your crimson grass will overtake regular grass, unless its prevented by stuff like sunflowers or wood blocks even.

After hardmode Crimson/Corruption (and the Hallow for that matter) becomes a lot more aggressive. They become able to overtake: Dirt blocks with grass, stone, sand and ice blocks. They will also do this at a much faster rate.

Bricks of any kind are unable to be corrupted, so stone bricks and the dungeon will never be corrupted. Wood too.

The jungle, last time I checked, can slowly be overtaken by the Corruption/Crimson during hardmode, which is quite a shame.

If you want the biomes to stop spreading there are different ways. Pre-hardmode you can use sunflowers or uncorruptable blocks like I mentioned. You can also dig a 4 block wide hole since the biomes cant spread over gaps that big. The most efficient way, but also quite expensive, is simply using the Clentaminator to change the biomes in an instant.

Hope this answers most of your questions!

[ShadeDaystar]

Originally posted by Vegito:

Also, does crimson take over snow biomes or the dungeon? My desert is between a snow biome and dungeon is it safe?

Don't forget that corruption spread isn't just horizontal. The spread could travel along the Cavern, or even Underworld, layer for the entire length of your map before traveling back up to the surface wherever it finds room.

Biome containment can be a hassle, but is usually worth it once you find something that works for you.

[ChaosFungus]

Originally posted by Vegito:

Also, does crimson take over snow biomes or the dungeon? My desert is between a snow biome and dungeon is it safe?

The Underground Ice Biome will still receive the same spreading effect, but the surface snow biome will not be as prone to Corruption/Crimson or Hallow, snow cannot be converted to Corruption, Crimson, or Hallow like Ice can.

[jiink]

my stats: 30something% corruption; 20something% hallow. ive done the celmlentator or whatever its spelled several times but it keeps spreading right back. :(

[ChaosFungus]

I simply used the Clentaminator with Blue Solution and apply the Hallow to my base, it will not interfere with liveability like the Corruption/Crimson will. While it will be more dangerous during Blood Moons if you aren't prepared enough, you do not need to worry about NPCs having to leave their homes.

[ShinkuTear]

Originally posted by But you said there would be cake:

my stats: 30something% corruption; 20something% hallow. ive done the celmlentator or whatever its spelled several times but it keeps spreading right back. :(

I reccomend wiping out annoying chunks of Corruption by replacing it with Hallow. The enemies are, IMO, generally less annoying to deal with, and Hallow looks much nicer then Corruption. NPCs also don't complain about Hallow.

[ChaosFungus]

Right now, my world is 53% Hallow and 24% Crimson, so I am happy that I can keep all my NPCs.

[jiink]

Originally posted by ChaosFungus:

I simply used the Clentaminator with Blue Solution and apply the Hallow to my base, it will not interfere with liveability like the Corruption/Crimson will. While it will be more dangerous during Blood Moons if you aren't prepared enough, you do not need to worry about NPCs having to leave their homes.

my base is pure which is great though.

Originally posted by ChaosFungus:

Right now, my world is 53% Hallow and 24% Crimson, so I am happy that I can keep all my NPCs.

hallowed is also critical for keeping your jungle safe from crim/crup. Im glad i learned that.

[Unicarn]

It has to be 4 blocks wide.