Some more factors:
Different woods have different expansion rates and brittleness. The higher the expansion rate, the more stress is generated from a given RH% change. The more brittle, the less drying stress it takes to crack the wood. wood-database.com has numbers for many species.
Redwood and western redcedar have extremely low expansion rates, but are brittle. So brace them dry to give low humidity tolerance, because they're not going to generate much stress in high humidity either way. Walnut, on the other hand, has fairly high expansion, but is tough so it can take a big drop in humidity. Brace it in more medium humidity so it doesn't swell up too much during those Florida summers
Ebony has extremely high expansion and is pretty brittle too, so it's just going to be trouble nomatter what you do.
Another thing is the hysteresis effect. Acclimating a piece of wood from 60% down to 40% RH will still be more swollen than if it had gone from 20% up to 40%. This is why sometimes if you have a braced plate sitting out and your humidity level drops for a couple days, the plate goes concave and stays that way even after the humidity returns to normal. You need to take it up to high humidity and then back down to the shop level to restore it. But to prevent it happening in the first place, use a standard procedure of drying wood out and acclimating up before bracing.
Different woods have different expansion rates and brittleness. The higher the expansion rate, the more stress is generated from a given RH% change. The more brittle, the less drying stress it takes to crack the wood. wood-database.com has numbers for many species.
Redwood and western redcedar have extremely low expansion rates, but are brittle. So brace them dry to give low humidity tolerance, because they're not going to generate much stress in high humidity either way. Walnut, on the other hand, has fairly high expansion, but is tough so it can take a big drop in humidity. Brace it in more medium humidity so it doesn't swell up too much during those Florida summers
Ebony has extremely high expansion and is pretty brittle too, so it's just going to be trouble nomatter what you do.Another thing is the hysteresis effect. Acclimating a piece of wood from 60% down to 40% RH will still be more swollen than if it had gone from 20% up to 40%. This is why sometimes if you have a braced plate sitting out and your humidity level drops for a couple days, the plate goes concave and stays that way even after the humidity returns to normal. You need to take it up to high humidity and then back down to the shop level to restore it. But to prevent it happening in the first place, use a standard procedure of drying wood out and acclimating up before bracing.
