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I picked up a bunch of Koa and Walnut that has good figure in it but.....
The wood got wet and hot and warped like crazy before I got it....

Any great ideas on getting these flat again?

I was thinking about a steam box with weight sitting on the wood

Earlex makes a steam generator that might help make it work...
Anyone tried to fix wood like this before?

spritz the concave side with water, go slow (as in multiple sessions) and they should come back relatively flat. water raises the grain of the wood so it will want to pull up, or bend back by putting the water on the concave side Water --> ) as a little diagram for you. Sticker the wood between sessions to get some weight on them.

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in agreement but with different wording:

look at it this way, the concave side has a smaller radius (by whatever the thickness of the wood is) than the convex side...spritzing water on the concave side will cause it to swell up and gain 'radius'...this will eventually lead to the radius of both sides = infinity = flat

I deal with plenty of warped koa here in Hawaii. Most of it will straighten, but depending on the cut, it may not stay straight. Best way for me to straighten koa is to wet it on both sides and dead stack it on cement heavily weighted. It will usually straighten overnight. Sometimes it might need a 2nd wetting and stacking. Then you can sticker it as you would any normal wood. If it does not stay straight after that, it's probably not very good wood to use.

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Ok ... I will give both methods a try and see what happens

Ya all don't think adding heat would be helpful? ( steam box ) or is that a waste of time & money ?

Forget the steam. Do as Pegasus suggests but leave it under weight for as long as it takes for the wood to reach the RH of your room. If you flatten it between two boards it can take days for it to thoroughly dry out.

Do not apply heat to wood with wax. Your wood seems wax free, so OK. If the other methods do not work for you, you may want to try what I did. I had a similar set of BRW that had wax on the ends. The wood was so stiff and hard that it would not straighten under weight, even wetted. Then, I soaked the wood in a sink for about a week. The first few days, the wood did not change, but eventually it got dead flat, returning to the condition it was at when sawed. Then I stickered it and it dried flat.

Do you have access to a hot plate press like a photo shop, t-shirt business, or sign shop might have? If you do, you can sprintz ( sometimes veneer softner if it is extreme ) and place between the plates with silicon blankets ( no elements.... just a blankets top and bottom ) start at about 180 degrees and work your way up to about 350 degrees in say a two hour period of time ( you may have to re-sprintz etc. we do check material periodically. ). We usually only do one complete set at a time. After about 2 hours of plate heat allow to cool naturally still in the press and the material should now be flat. As others have mentioned sometimes nothing works. We have used the above method with extreme curls and burls with great success.

Blessings,

Kevin

Try to stabilize it per the suggestions these guys have offered. As Bob has advised, if it does not eventually stay flat for quite some time (I would say many months), don't use it. My very first guitar has a back that looked perfect for a very long time. Then it went wonky on me. I keep it just as a reminder. Highly figured woods can be a total joy when they work out, but a real bummer when they go wrong. The back of mine was crotch grain walnut with a checkered figure. If I ever get around to replacing it, I can cut it up for head plates and such, but it'll never be a guitar back again.

Thanks Guys.. I just wet up a slightly warped back and places it on some concrete with bricks on top...
We shall see if there is any improvement .... The Koa is from a cut that was from a crotch in the tree so I am sure I will let it set stickered for some time if it does flatten out good. Do ya all think thinning in a drum sander is a good idea before straightening? these boards are at approx .220

Thanks for everyones help....

Dennis