Could be wrong, but I don’t think you can cook the zinc out of brass, at least not at 700-900F. I mean, where would it go?Supposedly, in a darkened room when you just see the faintest glow, that's the temperature. Certainly don't go by the color change of the brass.
The good news- it's better to under-heat than over heat it. You can cook the zinc out of it with too much heat. Then again, I watched a series of youtube videos where a guy completely overcooked his brass and couldn't tell a difference when he resized them.
I have an IR thermometer which goes up to 620F, so I just let it cook a second longer to get to 700. 308 takes about 2x the time in the flame as my 300BO for example.
Where would it go? The air? Where does wood go when you burn it...? According to this, zinc evaporates at 900F, which is just over the temperature that you want to anneal. Zinc undergoes sublimation (solid to gas), without a liquid phase.Could be wrong, but I don’t think you can cook the zinc out of brass, at least not at 700-900F. I mean, where would it go?
The brass gets soft, but I doubt that it’s a function of changing the alloy.
I do the darkened room thing with a drill and a socket. You've got to bring the temperature up quickly or the heat will travel too far down the brass. The neck and shoulder area is as far as you want to aneal. As soon as I see the faintest orange appear, I drop the case out of the socket.Supposedly, in a darkened room when you just see the faintest glow, that's the temperature. Certainly don't go by the color change of the brass.
Zinc can sublimate, it can also melt.Where would it go? The air? Where does wood go when you burn it...? According to this, zinc evaporates at 900F, which is just over the temperature that you want to anneal. Zinc undergoes sublimation (solid to gas), without a liquid phase.
I'm no metallurgist, but over-cooked brass has a different color- something is gone, and I heard it was zinc, but reading, it could be tin cooked out as well. The cases look more pink when they've been cooked.
You've got to bring the temperature up quickly or the heat will travel too far down the brass. The neck and shoulder area is as far as you want to anneal.