Rumor has it...

[UnderControl16]

that heat treating the belly of a bow to a nice golden color will both increase it's compression strength and weight. True or not? Your experience on heat treatment?

[Diamondback59]

the belly  yes back i aint tried

[UnderControl16]

sorry! typo meant belly.

[Stiks-n-Strings]

Don't heat any tropical wood. Found out from experience that Jatoba will fail big time.

[ChristopherO]

That's not a rumor but a fact, on many domestic woods.  Marc St Louis, a wood bow guru, heats his until they are burnt black, then sets them aside for a week or so to rehidrate before tillering.
I've had good success and overdone it and caused chrysals (frets) on bows.  It is one of those techniques that have been used for centuries by the Indians, as I've read.  As for upping the draw weight, yes, it does that as well.

[Silent Bear]

its true

[UnderControl16]

wait how can it be done wrong or over done because i got frets on my bow...

[UnderControl16]

ttt

[shamus]

wait how can it be done wrong or over done because i got frets on my bow...  

Frets are from improperly tillering or a improper design... or both.  You have to remove wood on both sides of the frets to relieve the pressure and correct it... if it can be corrected.

 
Regardng heat treating: heat treating of bows was done back in the 1930s, and bowyers now are doing it again. There hasn't been any scientific analysis/experimentation done to offer an informed conclusion one way or the other. It has a long history. Many have reported positive results, but the evidence is anecdotal.

One day someone might give heat treatment of wood a hard scientific look.. and THAT would be interesting.  

[ChristopherO]

"wait how can it be done wrong or over done because i got frets on my bow..."

By drying out the wood too much and not allowing it time to rehydrate before bending the limbs.  I'm a good hand at doing that.
I am leaning toward it is best to not have it totally tillered but floor bending before toasting the belly very dark.  Then shave off most of the burnt belly wood during tillering.  If it needs another round of heat treating then so be it but at least the original tempering should not overdry the belly allowing frets to form as easily.  
As I don't have knowledge of your experience level don't take this as a put down but poor tillering can, also, cause frets as excess compression on spots of the limb causes the wood cells to give way.  I've had it happen on non heat treated bows, as well.

[John Cooper]

It's real!     One of my buddies in the area toasted the belly of a hickory selfbow.  It's amazing how short and thin he was able to make that bow! He used a jig like the following (pardon my poor MSpaint skills!) to help him not get too close and scorch the belly:
 

As far as frets on the belly go, they're a really good teacher.  If you have frets in only one spot, it's a hinge.  If it's all along the belly, your tiller is great, but the design needs to be longer or wider for the poundage.  

~John

[Thwackaddict]

Correct me if I'm wrong but i do believe 4-6inches will work for that distance.

[John Cooper]

okay...so I found an article in the Bowyer's Bible volume 4 talking about heat treating and it's benefits.  The proper distance from nozzle to bow is about 4" and the time to spend in one spot is about 5 minutes.  You'll notice a pleasant aroma, but not any blackness.  Move down 2" and repeat.  It's best to use a reflex caul that's slimmer than your bow so the heat doesn't bounce back and hit the back of your bow making it brittle.  This'll be a different reflexing jig than I showed you before.

John

[Loren Holland]

I made a Cratemyrtle self bow, I heat treated as experiment, having never done it before, and figured it was just a sapling from a trash pile that I wasted if I screwed it up.  I put one tip on my kitchen island and the other tip on the counter, pulled it into reflex by hand and held the gun with the other hand. I need to get some jigs built. Long story short, it took some reflex and toasted the belly till black. I noticed an immediate jump in weight. (I didn't know about letting it rehydrate, fortunately nothing bad happened.) I tillered off the black part, and for a relatively light weight, whitewood, the bow turned out to be a pleasant surprise.

[UnderControl16]

Wow i don't visit the site for a couple of days and i come back and there is some amazingly helpful tips on how to heat treat bows. Thanks guys can't wait to try it out and see how things turn out. I will be sure to post pictures before the month is over. Trying to build my best two bows (one for me, one for the girlfriend (two different weights hence)) and two dozen "perfect" arrows for them...