From a luthier‘s Notes:
pegs made from torrefied sorb-tree wood
by Sebastian Stenzel 2021
As announced in ’Some thoughts on Pegs‘, I have started to make pegs from torrefied wood.
Every player using wooden pegs is familiar with the problem: the relative humidity (RH) drops, and as a result, one or several pegs jump loose and the string(s) unwind. Or, RH goes up, and the pegs sit so tight that you are afraid of breaking them trying to pry them loose. The reason for this is that wood adjusts its humidity to the surrounding air‘s RH, and swells when taking up water, but shrinks when giving water to the air. This swelling and shrinking is dramatically reduced by roasting the wood mildly without oxygen present, a process called torrefaction. It is actually remarkable that nobody has done this for pegs before, as this process of heat-treating wood is well understood for many decades. It is important to point out that torrefaction of peg wood must be done very carefully and only at the lower end of the temperature range. I got the best results with 200ºC, but in order to achieve a nice chocolate-brown colour, 220ºC are needed.
The pegs I turned from this wood are marvellous and show no decrease in stability and no reduced Young‘s modulus, but a weight reduction of up to 14%.
We have to wait for the test of time, but I am very optimistic that with such pegs, the above mentioned problem is sufficiently mitigated, if not eliminated.