Working with Problem Woods - Luthier Tips du Jour Mailbag
In this episode, Robbie O’Brien offers tips on working with woods that display minor defects.
Video Transcription
[on-screen text reads: Luthier Tips du Jour Mailbag]
Mailbag question: I have an exotic back and side set that I want to build a guitar with, it has some defects, should I use this set?
Robert O'Brien: Today's Tips du Jour Mailbag question comes to us from California. "Dear Robert, I have an exotic back and side set I want to use to build my guitar. However, it has some defects in the way of wormholes and knots. Should I use this set or do you recommend using another set? Thanks for all your videos, John, in California."
High quality exotic hardwoods are becoming scarce
John, let's face it. Obtaining high-quality exotic hardwoods for instrument building is becoming a problem. They're becoming scarce. So this is causing us as builders to have to hone our skills to be able to learn to work with wood that's less than optimum when it comes to quality.
Let me share a story with you. Years ago when I used to live in Brazil, I was sawing up some Brazilian rosewood logs in a shop. After a few minutes, I noticed there were some guys behind me, some old timers. So I turned all the equipment down thinking, "Hey, this is a great time to have a conversation." They wandered over to what I was doing and after a few minutes, one of them said, "You know, Robert, we used to throw away the wood that you're working with." In other words, the quality that I had was nothing compared to what they had 40, 50, 60 years ago. So this is the trend. This is where we're moving. The quality of wood that we're getting these days is nowhere near what we had years ago. But we still have to use it and work with it.
A good example of this is African blackwood. Now, African blackwood is a very dense member of the rosewood family that is harvested mainly in Mozambique. Many people consider this wood to be the most responsive wood that you can use for back and side set. Some even think that it surpasses Brazilian rosewood in total response. Take a look at these photos of some African blackwood lumber. LMI has done most of the hard work by sawing up these logs, riddled with inclusions, insect damage, cracks and knots, but the luthier still has some minor defects to work around if he or she wants to work with these sets of high quality wood. Now, there are some tricks you can use to work around these minor defects, and that's what I'm going to show you now.
How to work around minor defects
So here's a nice set of African blackwood that I got from LMI. But it has a few minor defects, some wormholes, a couple of knots, and some sapwood. Not a big deal though, and I'd really like to still go ahead and use this set.
Orient your template to remove defects
So here's a tip. When it comes time to lay out your side profile, place your template on there and orient it in such a way that you can go ahead and get rid of some of the defects, like some sapwood, maybe a knot, some run out, things like that.
Consider where your bindings are going to go
Something else to consider is where your bindings are going to go. If you have a lot of grain run out the side, perhaps you want to go ahead and get rid of that when you go ahead and narrow your sides down or cut them down to width. If you have sapwood or knots or things that could cause problems with the bindings and the routing of the binding channels, go ahead and try and eliminate that right from the start.
Place defect side on the inside of the guitar
Also, take a look at both sides of the piece of wood, perhaps the side that the defects on can go inside the guitar and the clean side, which this one has a clean side, can go on the outside of the guitar. Also, when thinning the sides, you can remove material from the side that has the defects. Perhaps the defects don't go all the way through and you can eliminate them all together.
Thin out defects when thicknessing
Now talking about thickness, African blackwood is a very dense wood, and to bend it, sometimes can cause some problem. So typically African blackwood, I take down below two millimeters thick or somewhere around 0.070", 0.070". Go ahead and drop it down as thin as possible, and that'll help you bend.
Fill in wormholes with CA glue and dust
Here's one of the pieces of the back, and I noticed that it has some worm holes or insect holes here that I would like to get rid of. Now, here's a quick way to do that. Just take a little CA glue and place right over the wormhole. Then come in with some sandpaper, create a little dust and that helps fill the void. And go ahead and add a little bit more CA glue. Repeat the operation as much as you need to go ahead and fill that void.
So the defect is a lot less noticeable now, and when you go in to do your finish work, your pore filler and that stuff will help hide those blemishes. If you find you have a little larger defect, you can come in and use like a two-part epoxy dyed black, and that also helps fill the void. I'll do this before bending the sides to help reinforce the wood, and if necessary, I'll do it after bending the sides as well.
After you've thicknessed your sides and you've taken care of any cosmetic or structural issues and it's time to bend, if you're bending on a hot pipe, you may want to reinforce any structural issues that you think could be some problem areas. For example, this is just a piece of hard maple, and you can use it to help bend places like around the waist or something on the hot pipe and reinforce the areas that perhaps will be a problem area.
Other tips for avoiding defects
When it comes time to join the back, use a very careful joining technique to minimize the waste. Also, when placing your template over it, if possible, orient your template in such a way that you can avoid problem areas or defects. Sometimes this is possible by just sliding the template forward or back or positioning it in a little different position when it comes time to draw out the outline. Also, when it comes time to choose what's going to be the inside or what's going to be the outside, take a good close look at the defects and perhaps any structural issues, and you can sometimes hide those on the inside of the instrument.
John, thank you very much for the question, and I hope you found the information useful. And remember, rather than discard a piece of wood that has some minor defects in it, now you know how to fix it and you can go ahead and use it to build your instrument.
[on-screen text reads: More Luthier Tips and online courses available at www.obrienguitars.com. Private and small group guitar building and finishing instruction available.]
