Author: Chris P
Date: 2021-08-04 01:01
Small leaks will increase the resistance and affect the response.
As well as the pads being a main culprit for leaks if they're damaged, porous, ill-fitted or not closing with enough pressure due to poor regulation or weak springing, the condition of the tonehole crowns are an important factor in how well any given pad will seal against it. Any small defects such as surface vessels, chips or nicks in them will cause a leak. Several small leaks will soon constitute to a significant leak and they will all need to be addressed. Low viscosity superglue is the best way to deal with leaks or imperfections, either with or without wood dust as a filler depending on the severity.
If all the pads are seating well and all tonehole crowns are perfect, both level and free from defects, other leaks can still happen which can be due to hidden cracks, natural flaws in the wood where large vessels can run into the bore from pillar holes, slots, tenons or any other countersunk features, beetle larvae damage (or 'worm holes') or manufacturing defects if tonehole inserts, speaker or thumb tubes haven't been glued in well or incorrectly fitted. With plastic instruments, sometimes there can be bubbles within the plastic as it was formed into the billet or during the injection moulding process and these bubbles only come to light once the toneholes are drilled or slots are milled.
Whenever any instrument is in for a service or an overhaul when all the keys are removed, it's always best to check all the joints are perfectly airtight without any keywork fitted by sealing up all the toneholes and one end of the joint, then doing a vacuum or pressure test to see how well each joint holds the vacuum or pressure, then the joint can be ruled out if it passes.
One way to pinpoint leaks is to seal up al the toneholes and ends of the bore, but fit an air hose into one end, then pressurise the joint and submerge it in water to see where the bubbles are emerging from. Then the leak can be dealt with by whatever method is best suited - most minor leaks can be sealed successfully by drawing low viscosity superglue into them.
In the olden days when dinosaurs once roamed the earth, they checked for leaks by blowing cigarette smoke into joints to see where the smoke emerged from. as well as the obvious smell of tobacco smoke that's not easy to remove, tar deposits can form where the leaks are and stain pads.
Sometimes things like metal tenon caps or socket linings can give false readings if they appear to be well fitted, but there could be a void under them to cause air to leak under certain circumstances. Again, superglue will wick deep into these voids and seal them up.
To conclude, superglue.
Former oboe finisher
Howarth of London
1998 - 2010
The opinions I express are my own.
|
|
The Clarinet BBoard
.jpg){kind=small}
.jpg){kind=small}
.jpg){kind=small}
.jpg){kind=small}
.jpg){kind=small}
.jpg){kind=small}
