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H.R.Fisher

Roasting tonewood

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  I have been reading about roasting guitar wood in a convection oven to darken the wood.  Would this process work for spruce violin tops?  Also what about putting tonewood in the microwave?

What effect might  this have on tone and structural integrity ?     Thanks,   Henry

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I'm told wood bursts into flames in the microwave. Dunno if it's just maple. Haven't tried myself.

 

 

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1 hour ago, H.R.Fisher said:

  I have been reading about roasting guitar wood in a convection oven to darken the wood.  Would this process work for spruce violin tops?  Also what about putting tonewood in the microwave?

What effect might  this have on tone and structural integrity ?     Thanks,   Henry

Roasting tone wood is an idea that many have tried. The general opinion is that, while giving an attractive color to white wood, it weakens the wood and makes it more brittle. A lot of old violins with baked tops are known for being quite difficult to deal with when repairs are needed.

Wood dealers in a rush to make sales will put wood in kilns to get rid of the moisture and make it look older than it really is, but this often has an undesirable effect. For that reason, many wood dealers make a point of assuring customers that their wood is air dried, NOT kiln dried. 

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2 hours ago, tamiya said:

I'm told wood bursts into flames in the microwave. Dunno if it's just maple. Haven't tried myself.

I experimented briefly with microwaving wood, and it is not anything I'd ever want to do on real tonewood.  The interior of the wood heats up to some uncontrolled temperature while the outside remains cool.  I had wood that was internally charred.

In a regular oven, you can control the temperature better and get some color change if you go high enough, but I don't think the properties are improved much.  I haven't spent all that much time with conventional oven processing, just enough to know it's not as good as other processes.

1 hour ago, The Violin Beautiful said:

Wood dealers in a rush to make sales will put wood in kilns to get rid of the moisture and make it look older than it really is... 

No kiln drying schedules I have heard of get high enough in temperature to cause color change.  I usually associate extremely white wood with kiln drying.  Normally kiln drying it only to get the moisture content safely and quickly  down to a decent level.  But there are no kiln police to make sure everyone is following the rules (there aren't any), so there may be folks who cook for color at higher temperature, as well as folks who try to dry things out too quickly and damage the wood.

What I do (torrefying) is not kiln drying, although it is kinda related.

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Kiln drying and roasting (or torrefying or baking, cooking ...) are two different things even some of the equipment used may be the same.

Kilning is to dry fresh wood or get already dry wood to target humidity in conrtolled manner. Extreme kilning may damage wood but most wood cutters who know their business are doing it properly and result is great defect free wood. Often kilning is preferable to uncontrolled drying outside in a "shed" where fungus, insects or heavy checking may ruin the wood without you knowing it...

I've done some simple baking in oven after reading many articles about thermowood or "torrefied" wood and you can get wood that is darker in appearance without any ill effects if you are careful. If I remember correctly I first heated the tops for hour or so at 100C to dry the wood to 0%MC then wrapped it in strong aluminum foil and carefully sealed with aluminum tape (heat resistant) to avoid oxygen (the big boys use nitrogen atmosphere) that would allow the wood turn into charcoal. I baked for 4-6 hours at 190C and got spruce that was slightly darker throughout and some of the resin got out to surface. After seasoning back to equilibrium humidity the wood remained a bit lighter (weight) than unprocessed wood. My test samples showed that different pices of spruce from different trees may darken to different shade.

I made two identical instruments out of identical pieces of wood all from same logs (even fingerboards) and the sound was the same but the baked top seemed to be more stable to humidity changes. So even if that's the only benefit it may be worthwhile.

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The movement of the wood is greatly reduced by stewing and drying several times.

Then heat it correctly, there is no damage and it is very stable, it is a process, not an afternoon in the oven.

It won't cup when you carve it, It cuts cleaner, it doesn't care if it gets wet a bit, not prone to warping .

I always do this, but when I have used  normal aged non kiln wood, it was very moody and a real pain.

I won't do it again. I think that most wood has internal stresses that need to be relieved.

You can leave these fiddles in a hot car in the sun, and no cracks, play around a campfire on a cold frosty nite, then hold the fiddle over the fire to warm it up, scorch the varnish a bit,,

no cracks, we can be rough on fiddles I know what they can take, I have to know,, it's just a box with strings to me, It's got to be right.

So I stand in the "camp" of Stewing the wood to some degree, depends entirely on the wood, some wood needs a bunch of cooking, other, just wet and dry, and by dry I mean hot and steamy dry, then reduce the moisture

An o2 free atmosphere makes a difference.

A guitar top could permanently shrink a long ways,,. better now than on the Deck I always say..

 

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