Globulisation!

[Terry McGee]

We’re often warned about “the dangers of Globalisation”. I’m writing on a much scarier concern, the danger of Globulisation.

I was contacted by the overseas owner of a flute that was behaving badly. It’s a modern flute, but not one of mine. It’s a simple style flute, conical, with no tuning slide or metal head lining. The owner complained that after just a few minutes of playing, it went really quiet, virtually silent. The only thing I could think of was severe moisture buildup, but I’d have to add, I don’t think I’ve ever come across a case that severe.

I asked the owner to get it into its sullen state, then look up the head with the embouchure hole under a bright light. Could he see moisture in the bore, and if so, was it in the form of distributed wetness, or globules?

Massive amounts of globules came the reply. And unable to be shaken or blown out. The body bore remained dry. He added that his other flutes dribbled from the end after playing. Not this one.

I then asked him for an appraisal of whether the flute bore was smooth or rough, and asked him to both look and also to run a finger around inside. (I remember my old German woodworker Kurt Kloska saying: “your best eyes are on the ends of your fingers”.)

Very rough, was his appraisal. OK, send it to me was my response. There’s a limit to what one can achieve by remote diagnostics!

It shows up, and sure enough, is really rough in the head. And I felt didn't play well even when dry. Considerably less rough in the body, presumably because less of the condensation could get down there. The flute isn’t made of one of our favoured flute timbers, but something more in the "nice furniture hardwood" range. When I removed the cap and cork, the bore up in that area was smooth, as off the reamer. So the roughness was the effect of accumulated water, not poor initial workmanship.

I asked the owner about what oil was recommended for bore care – he advised Almond Oil. And ventured that he thought the flute had been soaked in that by the maker.

So my conclusions are that the almond oil:
- had not proved at all effective at protecting the bore from roughening,
- that it was causing the moisture to bead into globules,
- and that the roughened bore now provided a secure footing for these globules to hang out and disrupt the vacillating air column. And wreak further damage to the underlying wood!

I’ve since sanded and polished the bore of head and body back to a reasonable semblance of smooth. It took a lot of sanding, and I was reluctant to do more, for fear of altering the bore dimensions! I’d characterise the new surface as smooth but with pockmarks where the moisture had made greater inroads. It was encouraging to play it afterwards, as the performance of the smoothed flute seemed considerably better than when it arrived.

I then soaked it in a drying oil for about a day, drained and wiped it dry, then put it out in the sun to cure, rotating it from time to time to spread the curing around the flute. The sun helped this process by making its way across the sky. Nice to have friends in high places...

That’s when I noticed something I’ve never noticed before – weeping of a clear liquid along the sides of both the head and body sections. Interestingly, the weeping came only from the “quarter-sawn” surfaces (the fine grain) and not from the “flat-sawn” or “plank-sawn” surfaces, the Cathedral Spires. Interestingly there was no sign of this weeping inside the flute, just on the outside.

This I imagine is some of the remaining almond oil that had been soaked into the timber, and was now being expressed because of the heat from the sun. And weeping from the quarter-sawn sides as these offer more mobility than at right angles to the growth rings. And drawn to the sun-warmed outside of the flute, rather than the darker inside.

All I could do then was to wipe this off, which became an hourly ritual. With the benefit of hindsight, it probably would have been a good idea to try to get rid of all the almond oil before adding my drying oil, but I’m not sure how that would have best been done. And I hadn't entertained the thought it would still be liquid!

I gave the flute a little test this morning, and it seemed fine, with no immediate sign of globulisation. I’m leaving it in the sun for another day, to cure the new oil before progressing further. The weeping seems to have subsided, which is presumably an encouraging sign.

I would normally go through the oiling, draining, drying, curing routine twice on one of my new flutes, but there may be an argument to do more here. To be determined.

Also encouraging is that the exterior timber is now looking “enriched” with no sign of damage where the weeping occurred. It looks “warmer” in colour and "deeper".

So, why am I telling you all this? A few reasons….

I’m wondering if anyone has come across this situation before, a flute brought virtually to silence by moisture globules in the head. I think I remember someone mentioning the build up of moisture globules inside a metal lined head, which we traced to the inside of the slide having been unnecessarily oiled. And dealt with by mopping out with a detergent-soaked rag, followed up by rinsing and drying with fresh rags.

It would also seem to be a bold statement of the degree to which a flute’s performance can be brought down by raised grain. More than we might have expected, but then this was really roughened grain!

Perhaps to question the efficacy of almond oil in protecting flute bores? It used to be the oil of choice back in the boxwood flute days, but maybe time has moved on?

And perhaps to remind us that our favoured flute woods got to be our favourites for a number of reasons, their density, fineness and moisture resistance being some of them. And that if you want to make flutes out of less ideal timbers, a non-drying oil may not be the best bulking agent. Something that soaks in and cures or hardens would seem a better choice.

But largely in case anyone else comes across this at-first mystifying experience. This might give you some thoughts on how to proceed! Or not to proceed, depending on what we find!

I’ll add more if I learn more from what happens next. And from when it returns to its owner and goes back into service. The real test.

In the meantime, very happy to be told where I could have done better!

[JTU]

My goodness Terry, weeping, cracking, rings dropping of, humidity, what oil is best if any (by the way I use macadamia oil on my wooden whistles to good effect) I’d say my decision to go with a Delrin flute looks better everyday. Does Delrin have a life expectancy? In the year 2224 will my Delrin flute still be being traded on the used flute market?
Cheers
JT

[Terry McGee]

We have certainly had a bit of a run of timber and oil issues lately! And I am expecting more as the planet warms and wooden flutes dry out more. Flutes made in England used to crack when taken to the US, Australia and India. Then of course they invented central heating, and the flutes started to crack in more locations. Then they invented climate change. What have they got against wooden flutes?

I can't think of any reason why your Delrin flute shouldn't still be in demand in 2224. Of course, if the Life-extensionist movement gets anywhere, you might still need it yourself!

It's more than ironic that long-life plastics are mostly used for the most trivial and short-lived tasks, think drinking straws, and its taken us a long time to get around to using them for long-life products. And given all we are hearing about micro and nano plastics being found in the food chain and now in our bodies, I'd go so far as suggesting that flutes are the only things we should be allowed to make from plastics!

[paddler]

Vacuum resin infusion using a product such as "Cactus Juice" from TurnTex completely solves this problem for a lot (not all) of woods that would otherwise make a sub-standard flute for the reasons outlined above.

To do vacuum resin infusion, you start by seasoning the wood as normal, then thoroughly dry it using a cook-weigh-cook-weigh cycle until there is no more moisture loss. Then you put it in a vacuum chamber, immersed in Cactus Juice, draw a vacuum, and watch every last bubble leave the wood (over a period of a few days). Then you release the vacuum and allow atmospheric pressure to force the Cactus Juice into the wood, again over a few days. Then you remove your billets and cook them at around 200F for a few hours to cure the resin. At that point you have billets with no ability to absorb any moisture, so no need to oil in the future, and you have a material that works and polishes to a fine finish, even if the original wood would have been quite rough. The resulting flute still looks, feels, plays and sounds like a wooden flute, but is maintenance free like like a Derlin one.

This definitely works, and I've made lots of flutes this way that have been universally well received. It also allows for some new experiments in aesthetics. But it doesn't work for all woods, and it is very expensive and labor intensive.

For woods to be amenable to this technique they need to be not oily, and they need to absorb a lot of resin. An oily rosewood won't work, but a low density fruit wood, or maple or walnut, or even a really low density wood like willow will work great. It works great on woods that are fine grained and normally (without resin infusion) would experience a lot of movement due to humidity changes, precisely because they absorb a lot. Interestingly, the resulting material machines very well, even when the original would not, and it is easy to get a smooth surface.

But expensewise, when I add up the cost of my time for all the preparation, the equipment, and the resin itself (which is obviously a consumable item), it is clear that making a flute from a premium flute wood such as African Blackwood is much less expensive, even compared to utilizing fruit wood that I harvested, milled and seasoned myself. Nevertheless, I do like the end result, and I like the fact that I can utilize domestic hardwoods in a relatively eco-friendly way.

[Terry McGee]

Very interesting, Paddler, and makes perfect sense. Ironic that to become a useful lattice for the Cactus Juice, the timber had to be really open grained.

So the flute I'm working with probably lies halfway between the premium woods such as Blackwood, and the more open timber such as you mention work well with Cactus Juice impregnation. It was obviously capable of absorbing some almond oil (the stuff that wept out in the sun). In hindsight, it would probably have been good if I had put it in the sun before re-oiling it, hopefully to extrude at least some of the oil that I could then perhaps have removed with a solvent or with detergent.

Since my initial account, I've given the flute a few days more curing time in the sun, and the weeping seemed to stop. And playing the flute convinces me it's now playing considerably better than when it got here, which is encouraging. I can't be sure how much of that is down to polishing the bore, as I also cleaned up the embouchure cut and finger hole undercutting, which I felt were deficient. Probably fair to say that gave half the improvement, and getting rid of the bore roughness gave the other half.

It now plays like a flute, and I'm not seeing any signs of globulisation. Fingers crossed we're heading in the right direction!

I've since re-oiled it, and am about to drain that, dry it off manually, and then put it back in the sun to cure again. It will be interesting to see if the weeping comes back!

[Terry McGee]

Oooh, interesting. You'll remember the weeping, which I reported as coming from the quarter-sawn planes of the flute tubes. I rationalised that as being the more readily mobile planes for liquids to pass through.

This morning the flute is back in the sun, and weeping is again noticeable, but now its moved to one of the "cathedral spires" planes, specifically the one facing the sun. The other side and the quartersawn faces are dry.

I've wiped that off, and rotated the pieces so the other cathedral spire face is now facing the sun. I won't be surprised if it weeps next!

Going to be a hot day today, so I'll probably give the poor flute a rest midday. The owner wouldn't be pleased to hear I'd solved the presenting issue but cracked the flute!

Again, no sign of weeping on the inside of the flute.

[paddler]

I wonder if there is still moisture inside the wood. Your description seems to imply that the surface in the sun is heating up, causing moisture to try to evaporate, which pushes the oil out of the surface. I've seen this kind of thing before with insufficiently well seasoned wood, although most notably on the end grain.

[Terry McGee]

I don't think it's moisture. It looks pretty clear (as much as you can tell - it's only weeping) and it feels a bit sticky, even after wiping off and leaving the flute out of the sun for a day or so more. So, I'm guessing it's remnant almond oil.

I can't think of any way to test the theory. I did wonder about wiping the flute with a cloth dampened in methylated spirits (denatured alcohol) to see if I could remove the "slightly sticky" feeling.

I should probably just leave well enough alone, let it cure a bit more, reassemble it and see how it goes in service!

[paddler]

I've seen and heard reports of makers who saturate their newly made flutes in none drying oils, and even some who have tried using vacuum infusion to force oil into the wood. I even thought about trying that myself at once stage, but then decided that it would probably be a bad idea because with shrinkage or changes in temperature the uncured oil would just get squeezed out of the wood and cause a mess on the surface. I wonder if something like that has happened to this flute? If so, probably the best solution would be to try to heat the flute to force as much of the oil out as possible, and then clean it off the surface before it becomes too gummy.

At least with the vacuum resin infusion approach I described earlier the cooking/curing process ensures that any resin inside the wood becomes solid permanently. But of course, if you get the cook cycle too short or too cool, you can end up ruining your billets because they are now saturated with a nasty liquid chemical that will now no longer cure. You've got to get it right the first time ... which requires a detailed understanding of the temperature gradients inside your oven or curing chamber.

[Terry McGee]

I've seen and heard reports of makers who saturate their newly made flutes in none drying oils, and even some who have tried using vacuum infusion to force oil into the wood. I even thought about trying that myself at once stage, but then decided that it would probably be a bad idea because with shrinkage or changes in temperature the uncured oil would just get squeezed out of the wood and cause a mess on the surface. I wonder if something like that has happened to this flute? If so, probably the best solution would be to try to heat the flute to force as much of the oil out as possible, and then clean it off the surface before it becomes too gummy.

I don't think I'd like to heat it any more than sitting in the sun was doing, but I agree that it probably was the old oil being squeezed out.

And after the second "oil, drain, dry, cure, air" procedure it definitely felt sticky, so gathering all my courage, I first wiped it off with a rag soaked in alcohol, then with a rag soaked in detergent solution, and then one soaked in clean water to rinse off. Then dried it off and let it air.

Coming back to it next day the stickiness was gone, so that's encouraging.

The flute is now playing much better, and the moisture seems to distribute evenly rather than form globules. So I think we are getting there.

[Terry McGee]

Some time has elapsed (almost a month - it seems much more!) since our last words on this topic. I thought I should round it out rather than leave it up in the air!

We'd got to the point that I'd done a lot of sanding and polishing of the bore, and given the flute two coats of drying oil. Discussions with the owner had us agree to doing a third coat (just to be sure, to be sure...) and the subsequent drain, dry, cure, air procedure, before getting the flute packed up and back off to him. It then took a while finding a flight to hitch a ride on, and threading its way through airports, customs, etc. Finally, I received a note back from the owner:

"The flute arrived safely. Looks like completely new! Lovely shine off it!
More to the point - lovely tone, and twice as loud!

None of the dreaded globules at the cork after extended playing!

Many, many thanks, Terry!! Much appreciated!

I’ll keep in touch with you re. how it progresses."

So, hopefully all's well that ends well. I guess the lessons are that the almond oil wasn't providing enough protection to the wood, and the wood had really suffered from the moisture, providing a lodging place for the globules. And so as time went by, the process of roughening due to moisture ingress accelerated, making everything worse. Hopefully the three coats of drying oil will provide more lasting protection. Only time will tell!

[Terry McGee]

And a reminder, before we get to smug about our nice blackwood or boxwood flutes that no flute is 100% safe from the ravages of moisture. (Well, maybe Delrin, but I haven't confirmed that!)

So, worthwhile to examine your bore from time to time, and see how it's going. It should generally remain shiny. If it's dull and particularly if it feels in any way less than smooth to the finger, you're probably losing a bit of performance, and increasing the rate of degradation, by keeping the moisture up in the head, rather than dripping on the fiddle player's knee, like it should do.

I have an old flute here in the Cupboard of Doom that was rescued many years back from Shearer's Quarters on a sheep property somewhere. It's totally filthy on the outside, but it's when you look up the bore to the light that you see the full story. This is a place where photons and sound waves go to die. You can only wonder at how it got to be that bad.