The immovable slide
A stuck tuning slide is one of the hazards of old flutes. You can see how it happens. The last player, perhaps sometime in the mid 19th century, had got into the very bad habit of not cleaning their flute after each play. Normally if you do that, you start to notice the slide getting hard to move and finally you get around to cleaning it before it sticks fast. But supposing the flute isn't cleaned at that point. The nasty organic compounds in your breath condensate continue working on the metals your slide is made from and effectively weld them together. In the case of an antique flute 100 years or so could pass before someone tries to do something about it.
Fortunately most "stuck" slides aren't really stuck or at least aren't very stuck and one or other of a number of methods will get them moving again. In approximate order of desperation:
But sometimes, the normal cures are not enough. I imagine this is when the condensate was thick enough and the delay long enough for very considerable chemical reaction to have occurred.
The case in point
The slide under discussion belonged to a Clinton Equisonant flute, made around 1860 or so. It uses the familiar head, barrel and slide arrangement of 8-key flutes. The slide was jammed entirely closed and it was clear from examining it that many previous attempts to un-stick it hadn't worked. That was confirmed when all the usual methods outlined above failed to achieve anything at all.
So what do you do then? Make a new head and barrel? Give up without a fight? Never!
The good thing about being in this position is that you don't have much to lose. Indeed, the owner was already resigned to the idea that a replacement head and barrel was in order. The biggest problem was that I couldn't get to the slide to work on it in isolation. I decided to remove the two wooden sections from the frozen slide to get better access to it.
Removing the barrel
Barrels are usually mostly a push fit on the outer slide, often with some shellac to fill any gaps. The lower end of the outer slide though is usually spun out, to prevent the slide pulling out of the wood. The spun out section is visible at the bottom of the socket and can be turned off with a boring tool.
Once the lip has been turned off, the outer slide can be pressed out of the wooden barrel using a mandrel turned to the right size to engage the slide, and a delrin split collet to grip but protect the wood of the barrel.
So now we have the barrel wood off, but the barrel slide is still firmly stuck to the end of the head slide, itself still in the head. We now have pretty good access to the outer slide - surely a little heat will get it moving now?
No such luck - even raising the temperature so high that the tin plating on the slide was melting failed to dislodge the slide. About this point you start to wonder if someone in the 19th century was playing a practical joke on you. Indeed, the smell emanating from the slide was reminiscent of old hide glue. Could it be the evidence of the meanest trick every practiced on a flute player?
Removing the head
Nothing for it but to press on and remove the head. The head already had a crack running down three quarters of its length, so I figured it shouldn't be so hard to get off. Even if the crack went all the way, or had to be induced to go all the way, I'd still be ahead (ahem!). A full crack can be re-glued just as easily, perhaps more easily than a partial one.
In the event, the inner slide pressed out of the head easily and without damage, using the same mandrel approach mentioned above.
Splitting the slides
With the pair of stuck slides now naked before me, it was not hard to separate them, again using a mandrel and press arrangement. Quite a bit of force was needed, and it was observed that the entire mating area was covered with a black carbonaceous coating. So it does seem as if something other than breath condensate might have been in there. I guess we'll never really know.
Where to from here?
Obviously a lot of cleaning up is in order before the slides can be reused. Indeed, in the worst case, one or more new slides can be made, although that appears unlikely to be needed. The wooden bits all escaped unharmed, apart from some minor signs of stress where previous attempts to separate the slides had failed. The same applies to the rings, but nothing that can't be touched up.
The pre-existing crack to the back of the head needs to be repaired, but that presents no difficulties. The repaired head and barrel will be re-bored to accept the slides without stress, and the slides will be cleaned up and reinstalled.
Quite a few really:
A myth debunked
There is a myth rampant that a few puffs of warm air into a cold wooden flute can be enough to trigger a crack. I've already researched and reported on the improbability of that in Effect of Heat and Cold on Wooden Flutes.
Consider what this poor flute went through on the way to the solution discussed above. Determined to give the hot mandrel approach every chance of working, I heated the mandrel until the steel was turning blue, then left the mandrel inside the tuning slide for over a minute, continually testing to see if the barrel would come free. It got to the point where I could no-longer hold the wooden barrel in my unprotected hand, yet the barrel did not split. The heat I was feeling had to be conducted from the slide inside right through the wood, so internal temperatures were really high.
Halfway through the process, I tried the effect of heat again. At this stage, the barrel was off, and I applied the heat of an oxy torch directly to the barrel slide, still stuck on the end of the head slide, still mounted in the head. Now remember that the head was already cracked from the top down to near the bottom. Here's me heating the slide until the tin plating is melting and yet the crack has not extended any further. So what can we reasonably expect from a warm puff of breath?
An interesting problem with some valuable lessons to be learned. I'll report back here when the head and barrel are back in business.
Now I need someone to write a 12/8 tune called "The Immovable Slide".