I was just talking with Geoffrey Ellis about his experiments with vacuum resin infusion. I don’t know if other flute makers have tried this technique before, but it sounds really interesting.
Quick summary of the vacuum resin infusion process: a piece of wood is placed in a vacuum chamber. The vacuum pulls all (well most) of the air and moisture out of the wood. Resin is then pumped into the chamber so that it surrounds the wood, and the vacuum is then released, allowing atmospheric pressure to force the resin into the wood. The resin-filled wood is then placed in an oven to cure the resin. The result is a dense flute-making material that is part wood and part resin, infused together. The ratio between wood and resin depends on the type of wood you start with. When done properly the resulting material is relatively impervious to water. Think of a wooden flute with the durability and maintenance-freedom of a delrin flute.
This technique is not just interesting as a way of improving the stability and durability of traditional flute woods (and I guess the jury is still out on how well it would work with very dense, oily woods), but it also opens up some interesting new opportunities to use materials previously considered inappropriate for flute making, such as low density, highly figured, woods and burls. With these woods, especially, it is not just a way of coating the exterior of the wood. It really forces the resin deep into the wood. For example, in one experiment Geoffrey did, a billet of curly redwood (a light, highly figured soft wood) started out weighing 1 pound and ended up weighing 3.5 pounds after vacuum resin infusion! Similarly, some burl wood more than doubled its weight.
In these cases I suppose it is debatable whether the flutes are “wooden” flutes or “resin” flutes. I guess they are both. They certainly “look” like wooden flutes. I’d be really curious about their feel and playing characteristics. As for looks, here is a picture of a vacuum resin infused Pratten flute made from the Curly Redwood I mentioned earlier.
Geoffrey’s blog has more details about the vacuum resin infusion technique, and pictures of his vacuum chamber and curing oven set-up.
Wow…that’s pretty. I’ll be interested to see how these flutes handle the rigors of flute-hood over the course of the years. A good wood flute, delrin or ebonite flute will essentially go on forever with occasional maintenance and repair, but I know dymondwood (or however you spell it) hasn’t fared as well.
Thanks for starting this topic, Jon–I’m very excited about this new process.
The question of how these flutes handle the long-term “flute rigors” is one that interests me. A lot will depend upon the wood itself, of course. While resin infusion does harden the wood, it contributes far more to density than it does to hardness.
A blackwood flute is really, really hard. You can bang them around pretty good without leaving a mark. A piece of resin-infused curly redwood is heavy and gorgeous, but if you bang it against something hard you can scratch and dent it more easily. So how the flute wears over time will depend also upon the player and how carefully they handle their flutes. In the case of figured softwoods, you get an eye-catching a beautiful flute, but the price is that you don’t spear your amp with it during the finale of your set.
I’m curious about the cast bore process as well (not in trying it, but simply in seeing it done). It actually looks like quite a lot of bother as well I wonder how the wood will fare on the outside of the lining. Will it be like a metal lined head where the wood might shrink over time? Does the cast material compress at all if the wood shrinks?
In theory, the resin infused wood will not move again during it’s life. I have not been able to test this theory because I’m just making my first resin flutes, but I think the theory is sound. The wood is sucked dry of air and moisture then saturated with a lot of resin. Complete saturation is impossible, but so far the woods take on quite a lot of the stuff. When it hardens, the wood is petrified, which of course is the whole point. I wanted to make flutes that you didn’t have to oil and didn’t have to worry about shrinkage. They should be fine in cold climates as well as hot, dry climates.
I’m planning on doing some stress tests. I’m making some resin-infused wooden tubes with one threaded joint. Once they are “finished” I’m going to be putting them through some harsh experiences, such as freezing them solid and popping them in a 200 degree oven. Maybe repeat the process a few times to see how robust the resin makes them.
I’d be curious about how these flutes behave with sweat. One of the drawbacks of resin flutes is that they start to feel “greasy” under the hands after a while. Wood doesn’t so much, I suppose because it has places for the moisture to hide. Which would these flutes be more like?
Reviol’s flutes combine the two of course - an impermeable resin inner, and a permeable wooden outer.
Well the wood is finished both inside and out, so the player isn’t actually touching the resin infused wood itself. Inside, the flute has a finish of marine epoxy and outside it has multiple coats of a CA glue finish topped with wax. So handling the wood should not be unlike handling a lacquer finish.
This is something I am looking into as well. One advantage of this is that it would allow a wider selection of locally available woods to be used for flute making. Blackwood, Boxwood and Mopane might not be available in the future eventually.
I know that acrylic impregnation doesn’t work with hard and dense woods such as blackwood. Its more suited to softer woods like pear and maple. It more or less doubles the weight of the wood, putting it into the density range of blackwood, and eliminates the porosity of the wood. It should work great for flutes and other woodwinds.
Am hoping to try this sometime this fall. I’ve been so busy making flutes this year that I haven’t had much chance to experiment and innovate! Fortunately the woods I have work well for me and my flute clients.
Yes, part of my own motivation had to do with the rarity of many flute timbers. I think resin infusion would do little for a dense, oily wood. Maple drinks up resin, and I suspect most similar woods will respond well. The trick is getting all of the moisture and air out of the wood first. Unless it is pretty well dessicated it won’t maximize resin absorption. This means that a nice, strong vacuum has to be sustained for a long time (several days or more, depending upon how dry the wood is to begin with). Then the resin has to be introduced without releasing the vacuum. This is the tricky part (and why I had to get a special chamber). If you release the vacuum to introduce the resin, the wood can absorb a certain amount of air (and atmospheric humidity). Then you have to extract that air again while the wood sits in the resin, which can take quite a while.
However, the ability to have domestic woods such as maple, walnut, cherry, etc. that are the density of blackwood opens a lot of possibilities. By the time you add the resin you aren’t necessarily saving money on the wood (a flute billet that drinks $20+ worth of resin is suddenly quite expensive) and you are definitely adding more labor, but in the future some of the tropical timbers might simply be unavailable.
I’d be very interested in the results of this as well- my wooden flute still expands and contracts daily despite it being 3 years old and well-maintained with regular oiling and proper humidification. It’s a real pain, and with plans for a nice 8-key in the works, I really don’t want to worry about suddenly being left without an instrument.
I’ve never seen any resin-infused woods (of the size needed for flute making) available commercially. I’ve seen very small pieces that can be purchased, but these are for things like pen blanks, knife handles, etc.. There are services that will do resin infusion for you, but I gather that it’s pretty expensive. My own conclusion was the the DIY approach was the only approach.
Yes, most emphatically the wood has to be seasoned in the sense that it must be completely dry. The drier the better. In fact, you can’t get it dry enough just by air drying the wood, you need the vacuum chamber to completely reduce any trace moisture content.
After the resin is infused, it must be heat cured but after that no seasoning required (except salt and pepper, of course
I’m going to be making some more Prattens’ from things like curly maple, osage orange and plum wood to see how they handle the resin process.
I’ve made an Osage Orange Pratten before, but I went to great lengths to stabilize it (this is before I had the ability to do resin infusion). It makes a great flute and it is very beautiful looking.
I’ve got a great video that I shot on my phone of Kevin Crawford playing this flute
It is a striking wood but definitely a candidate for stabilization.
Hmmm..I’m trying to post an image but can’t seem to figure it out. Can anyone assist?
Aside from the aesthetic value, what does this process gain over user a completely resin flute, such as the delrins made by many of our favorite flutemakers? Seems to me that, once you isolate the wood from the inner walls of the tube, you basically have a resin flute. I can surely appreciate the beauty afforded by exotic (or non-exotic) woods, but does this process do anything for the sound?
Aside from allowing a pretty smooth bore cut on woods that would otherwise not cut smoothly, I don’t think it is bringing anything sonically superior to the table.
It’s an aesthetic thing. The wood doesn’t really become very “plasticky” as a result of this process–it certainly retains a woody quality. I’ve made flutes from delrin and this feels very different. Delrin has many advantages, not least of which is superior strength and impact resistance that a resin flute won’t really match. But in terms of being maintenance free I think these are in the same league, or at least very near.
However, the idea behind the process (from my perspective) is that you get to have flutes made from beautiful timbers that would otherwise not be possible (or at least not advisable). As Casey observed, there are attractions to this as some flute timbers become scarce and the ability to use lighter, domestic woods starts to be a feasible option.
But in the end it is mostly about looks. I appreciate blackwood, mopane, boxwood and such as much as the next person, but they don’t provide much visual variety. I’m in the camp that says sound first, appearance second. If this process allows for a flute that can stand in line with any of the more traditional timbers and be eye candy at the same time, then I’m all for it!
Off topic, but what a lovely flute. Two original heads. Looks like the serial # is around 14xx, fairly early before the floating pad key construction by Monzani. Yet the holes for RH notes are larger than the Monzani I have which is serial 24xx. How does it play?
Lewis
I was trying to insert this in my earlier post but couldn’t figure it out. Hoping this works. We were speaking of Osage Orange, and this is an example. I’m stabilizing some of this wood right now. This is a great flute wood, but I wouldn’t trust it very far in without some type of stabilization. This one benefited from a generous amount of epoxy and CA glue.
I wonder how the wood will fare on the outside of the lining. Will it be like a metal lined head where the wood might shrink over time? Does the cast material compress at all if the wood shrinks?