Author: Clarimellonet
Date: 2019-03-11 08:16
I both perform extensively on and build boxwood classical period clarinets. Here's what I've learned over the years though building with boxwood:
(by the way, I'm referring exclusively to Buxus sempervirens and Buxus macowanii, not the "castello" boxwoods which aren't true boxwood species and therefore have different working characteristics)
Seasoning is important. The 17th and 18th century woodworking treatises I've read have suggested everything from natural drying over a period of several decades to burying logs of boxwood in manure (the idea being that osmosis will suck the moisture out of the boxwood into the manure and that after a certain amount of time, the wood will be moisture free. Some of the other methods cited mention specific ways to stack wood to allow the most airflow to allow the moisture to leave the wood at a controlled rate. What is almost never mentioned favorably is the kiln drying method that is commonly used now which "shocks" the wood into drying through the introduction of heat, the idea being that any wood which doesn't crack or warp during this process will be stable and safe to work with. The problem is that this can result in relatively brittle and dull sounding wood (which can still crack). I've always favored a long game approach to seasoning my wood. I was very fortunate in the beginning of my instrument making career to come across boxwood that had been sitting for 45 years. Today I use wood that's been aging since the 1960s and is a joy to work with. The main takeaway is that accelerated drying results in slightly less stable wood than aged and appropriately seasoned timbers.
My teacher once told me "if a piece of wood is going to crack, it's going to crack. If it's going to warp, it's going to warp." Unfortunately, that's very much true, especially with boxwood. One of the reasons clarinet makers began to move away from boxwood is because of the highly changeable nature of the wood which was frustrated by the addition of more keys and posts mounted into the wood. It swells faster and more readily than grenadilla, it needs to be re-reamed more frequently, and it is more prone to cracking and endgrain checking. However, the sound in my opinion is unmatched and I love playing on my boxwood instruments more than my grenadilla ones.
So how do we stabilize boxwood? In short, we can't - we can only make it less unstable. Oil is the key. I've been using linseed oil for years especially inside the bore of new instruments I've just made. After I do the final turning and drill the tone holes, I submerge the entire instrument (with no keys, no register tube, no metal whatsoever) in linseed oil for up to a week or so to absorb as much as possible and then I let it dry. The linseed oil polymerizes over time and forms a protective layer of what is essentially a plasticized oil which seals off the pores of the wood, especially in the endgrain where most moisture is absorbed. I polish the bore to remove the excess oil, use 0000 steel wool to remove the excess on the outside and buff the finish, and do it again. I do this at least 10 times, the end result being a piece of boxwood relatively impervious to water absorption. However, hours of playing and swabbing will eventually wear through this coating, and when I reream the bore the original dimension every couple of years, I'll repeat the process.
For those looking for a quicker fix, some period instrument makers will artificially seal the bore with marine epoxy in a series of very thin coats. Git-Rot is the standard. It mixes easily, absorbs quickly and cures in about 3 days. Mix up a small batch, coat the bore, endgrain, and sockets and let it absorb. Polish away the excess with 0000 steel wool and repeat. Most of the makers that I know who use this stuff on boxwood say 3 coats is a good starting point.
Again, none of these will prevent cracks, splits, or warps, but they will make the wood more impervious to water, which is a major cause of these issues. Boxwood can be a great wood to work with, but incredibly temperamental. Keep oiling and aging the wood, and you'll have a good short at getting some workable pieces. Good luck!
~Thomas
Thomas Carroll
Historical Clarinets and Chalumeaux
http://carrollclarinet.com
lotzofgrenser@gmail.com
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