Roasted Mahogany Test

[aguyinaustintx]

I am contemplating a build that uses a roasted mahogany body. My thinking is that roasting mahogany will darken the color and reduce its weight, so I decided to try it in a conventional kitchen oven.

The first test was conducted by breaking off part of a scrap mahogany headplate veneer board, approx. 1/8" thick. The piece was placed in the oven before it was turned on. The temperature was slowly brought up to 360 degrees F over the course of 1 1/2 hours. It was roasted at 360 for one hour. The kitchen had a bit of a fireplace smell, or as if something unfamiliar was being baked. The oven was then turned off, and the piece was taken out after it reached room temperature. The piece was glued back on to the unroasted board. The board was crudely finished in a few layers of shellac to approximate the finished color. The piece appears to the left in the photograph below.

The next test was run on a piece of mahogany approximately 1" thick. The baking schedule was similar to the previous test, except that the 360 degree phase lasted for 1 1/2 hours instead of 1. The toasted piece was cut into two, and one piece was finished in shellac. The results appear below. An unroasted piece is included, with one half of it finished in shellac. Prior to roasting, the piece measured at 8.6% moisture using a pin-style moisture meter. After roasting, the moisture level was too low to register on the meter.

I like the resulting look. My next step will be to roast a mahogany electric guitar blank.

 

[AirCap]

I could be wrong, but roasting (or Torrification) of the wood is done at lower temps....

Also, unless the body is a single piece of mahogany the glue joint could fail from the heat and then you'd have a multi-piece body. I did that once back in the 80's trying to dry out a stained mahogany body. NO BUENO.

 

[Cagey]

I was under the impression it's an oxygen-free process as well. Not sure why - maybe prevent combustion?

 

[mayfly]

I was under the impression it's an oxygen-free process as well. Not sure why - maybe prevent combustion?

Yep that'd be why.  BTW - welcome back Cagey!

 

[Cagey]

Thanks! Good to be back! Exercise off the being bedridden thing, and I should be good as new. It's amazing how fast your body gets used to doing nothing.

 

[aguyinaustintx]

Thanks for the comments, everybody. Great to hear that you're doing better, Cagey.

The roasting would be done to a single-piece wood blank before it's made into a guitar body, so glue joints would not be a concern.

Various internet sources quote a combustion temperature of 300 Celsius (572 Fahrenheit) for wood. Wikipedia states that torrefaction is typically done between 200 and 320 Celsius, albeit in an oxygen-free environment. My test was at 182 Celsius (360 Fahrenheit), and there was no charring or anything to suggest that combustion was imminent. After all, food is baked at this temperature without igniting.

I like to put conventional thinking to the test, and plan to roast a mahogany guitar blank arriving soon. Stay tuned!

 

[Cagey]

I understand your POV, but I wonder if you're aware you can buy roasted Mahogany blanks pretty reasonably here? Might save you some grief.

 

[aguyinaustintx]

I understand your POV, but I wonder if you're aware you can buy roasted Mahogany blanks pretty reasonably here? Might save you some grief.

Thanks. I called them last week to ask about those pieces. Someone took a message, and no one called me back.

 

[BroccoliRob]

Lol, I could be totally wrong, but I doubt the Big W wants to work with something you put in your kitchen oven for a while, I don't think that accomplishes the same thing, my Edgar Allen Bro.

 

[musicispeace]

I was under the impression it's an oxygen-free process as well. Not sure why - maybe prevent combustion?

I have heard that too. Someone told me two or three years ago that they have to reintroduce a little moisture back into roasted maple after roasting to make it like 6%. The science of all this really interests me.

 

[ByteFrenzy]

It wouldn't necessarily have to be combustion, rusting is also oxidation for example. Heating the wood to this level of temperatures is going to release all sorts of fumes, some of which could combust, while others will combine with oxygen at a more leisurely pace. But all of them will introduce random effects into the end product which is not what you want. You let the thing sweat away from oxygen to get a consistent output product.

 

[aguyinaustintx]

Musicispeace, I too am interested in the science involved here. It would be nice to hear from someone with a background in wood science, or with first-hand experience. I do understand that torrefaction per se requires an oxygen-free gas. With oxygen in the mix, the results may be different. Perhaps noxious chemicals will be produced, but my suspicion is that this is species-dependent. Hopefully coffee beans, cinnamon bark, flour, nuts, and other organics people have been roasting don't product anything too noxious. Still, roasting wood at home falls in the category of "try at your own risk", and I am not recommending that anyone do this. However, I went ahead and roasted a billet of mahogany in my home oven, and it came out looking really nice. The aroma was pleasant, somewhat similar to roasted almonds. The roasted mahogany will be used in my next build, to begin in early 2020.

 

[Cagey]

My understanding is the "oxygen-free" environment is to prevent combustion/oxidization, not reduce the risk of creating of noxious/toxic gases.

 

[aguyinaustintx]

The mahogany was roasted at about 175 C, which according to various sources, is below the oxidation point for wood. Sources:

Stages of Wood Burning Combustion
http://www.flameandcomfort.com/archives/blog/311

Pyrolysis
https://en.wikipedia.org/wiki/Pyrolysis

Maillard reaction
https://en.wikipedia.org/wiki/Maillard_reaction

Torrefaction
https://en.wikipedia.org/wiki/Torrefaction

 

[Rick]

Mahogany toast ... mmmh good.

 

[aguyinaustintx]

Here's the roasted mahogany, sandwiched between a walnut top and bottom, finished with Tru-oil and topped off with spray semi-gloss poly. Home baked, looks mmmh good to me!

 

[DangerousR6]

Thanks for the comments, everybody. Great to hear that you're doing better, Cagey.

The roasting would be done to a single-piece wood blank before it's made into a guitar body, so glue joints would not be a concern.

Various internet sources quote a combustion temperature of 300 Celsius (572 Fahrenheit) for wood. Wikipedia states that torrefaction is typically done between 200 and 320 Celsius, albeit in an oxygen-free environment. My test was at 182 Celsius (360 Fahrenheit), and there was no charring or anything to suggest that combustion was imminent. After all, food is baked at this temperature without igniting.

I like to put conventional thinking to the test, and plan to roast a mahogany guitar blank arriving soon. Stay tuned!

The oxygen free environment or vacuum is much like the process used in heat treating steel as well, the lack of oxygen helps prevent oxidation obviously and also to promote stability. Parts can be machined to size and heat treated in a vacuum so that there's no shrinkage. I would think wood is possibly similar... :dontknow:

 

[rgand]

The mahogany has a nice color to it. Roasting woods sure does make some fine looking pieces. Looks good.

 

[Rick]

Looks so good.

 

[66 Degrees North]

aguyinaustintx, I literally joined this forum to ask you if you noticed any shrinkage to the mahogany billet after baking, if so how much and, how torrification might have affected gluing (for better or for worse)?