I'm making a maile hauberk from mild steel and was wondering if there's any way to blacken it once I'm done to prevent rust. I've cold blued some blades before but I'd imagine that would not be easy to do with maille. Are there any good ways to blacken maille (preferably without too much heat)?

I've blackened mail by coating the maille in oil and cooking it. It's a really dirty process. You and your clothing get blackened when you wear it. Not recommended.

Yeah I've been reading about people cooking it and it not turning out well. I read where someone cooked it in an oven and it turned out ok so I might try that.

Though I don't know if it's a historically accurate method for the purpose of this thread, there is a natural way of dying animal traps that's been around a long time using one of various types of tree barks, leaves or berries. It involves letting the metal develop a light coat of surface rust after degreasing, and then boiling the metal with the bark, leaves, or berries until the metal develops a nice black rust resistant coating. My brother has used alder brush to good effect though a gentleman in this thread http://www.michigan-sportsman.com/forum/threa...ye.207561/ (see posts 4 & 7 for method) uses maple bark with good results. I don't know how well it would hold up to wearing off on clothing, but it does seem like it could be a historically plausible method.

Whatever method you try, you might want to consider doing "test strips" first: make a few inches of chain or a small patch of maille a few inches square from leftover rings and try anything out on it first. It should be readily apparent if the small sample is unworkably greasy or dirty without turning a whole maille shirt into a drycleaner's nightmare.