 The Clarinet BBoard
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Author: Bennett ★2017
Date: 2006-02-24 02:58
I've often seen it recommended that a good way to check for leaks is to stick a sock in the bell, close all the holes, remove the mouthpiece and suck. Is this better than doing the opposite - blowing?
It seems that trying to force air out of the pads and joints would be a better test that everything is sealing correctly. Why is the vacuum test valuable?
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Author: Chris P
Date: 2006-02-24 03:21
A better way to check for leaks is testing each joint individually rather than testing the whole clarinet. Ideally the whole instrument should be airtight and some can only be tested like this as they are in one piece (ie. most Eb clarinets and some one-piece bodied Bb clarinets) - but without the bell or barrel.
In most factories, instruments are tested with a machine that blows air into each joint while the fingerholes are blocked with Blu Tack and the open end stopped with a rubber bung, and the dial reading should be as low as possible to pass quality control.
But how many people have access to this kind of machine? The simplest and most accessable way is to see if each joint is airtight is by sucking the air out and seeing how long or short the vacuum holds for.
Obviously the vacuum has to hold for as long as possible, and I set my target for anything over 10 seconds on any clarinet I fully overhaul (though I can get a vacuum to last for well over 30 seconds), whereas a new clarinet will probably only last for a few seconds - in single figures at the most (mentioning no makers here whatsoever) which isn't good.
Former oboe finisher
Howarth of London
1998 - 2010
The opinions I express are my own.
Post Edited (2006-02-24 16:47)
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Author: Jack Kissinger
Date: 2006-02-24 04:50
I would say do both - but as Chris says, one joint at a time. The potential problem with the suck test is that, in creating the vacuum, you may pull a slightly leaking pad closed, masking the leak. So, if the joint fails the suck test, you almost certainly have a leak. If the joint passes the test, however, you may still have a leak. On the other hand, the problem with the blow test is that it puts more pressure through the joint than normal playing and may force a pad open, particularly if its spring has light tension, giving the impression of a leak. So, if the joint passes the blow test, you probably don't have a leak. If the joint fails the blow test, however, you still may not have a leak. Together, however, the two tests give you a fighting chance of finding out if you have a leak or not.
BTW, in the "good old days" some repair techs tested for leaks by blowing cigarette smoke into the instrument and seeing which holes it came out. Yecch! Not with my clarinet, you don't.
Best regards,
jnk
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Author: susieray
Date: 2006-02-24 05:39
My local repair guy still keeps a cigarette on hand for that purpose but I don't think he uses it very often. Mostly he does the suction thing.
Sue
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Author: Paul Aviles
Date: 2006-02-24 09:16
Dear Jack,
I have to disagree with the "possible no leak with a blow test." There IS pressure when we play and surprising little can cause the pad to leak. The biggest area for this is the right hand Eb/Ab key - you CANNOT adjust this key to a hair trigger and get the bottom notes to play well. The "leak" will manifest itself as a more flacid sound, and may not affect "getting" the notes, just how solid they are.
And for those of you with Rossis, yes you have a harder time with this in that it becomes less of a pinpoint test. For this, you guys definitely need a feeler gauge.
...........Paul
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Author: David Spiegelthal ★2017
Date: 2006-02-24 12:09
Suck to check for leaks, blow to check for weak springs (pads blowing open, especially the Ab/Eb which has a short spring that is frequently not strong enough).
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Author: BobD
Date: 2006-02-24 12:33
"Sock it to me, Sock it to me".....If the sock is not clean then blow. In any event a sock won't seal the bell adequately. Remove the bell and seal the end tenon with a rubber "cork".
Bob Draznik
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Author: Bennett ★2017
Date: 2006-02-24 21:34
Why test one joint at a time? Surely leaks can occur between the joints. Or are the one-at-a-timers suggesting that the whole instrument be checked after each joint is individually checked?
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Author: tictactux ★2017
Date: 2006-02-24 22:18
> Why test one joint at a time?
I guess for simply practical reasons. The odd bottle cork to close one end is always available, and you still have a hand free to scratch your head.
When you have ruled out the pads, then you can run some tape around the joints (when the clarinet is assembled) and check if it's getting any better.
--
Ben
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Author: Gordon (NZ)
Date: 2006-02-25 01:50
For detecting leaks, I don't suck or blow.
I gently SQUIRT out a MOUTHFUL of air. By doing this I can accurately detect just how MUCH air is leaking while I maintain low pressure.
My hunches regard suck as pretty unreliable compared with squirt. After all, we are trying to detect leaks at low pressure, not the considerably higher pressure (drop) typically involved with a suck. Besides, as somebody mentioned, a suck could mask a leak by drawing an offending pad towards the tone hole.
I only actually blow to determine WHICH pad is leaking, because more often than not, with extra blowing pressure, air hisses from the offending area, and the key involved can be detected by using the OTHER hand (hence "Why test one joint at a time? ... so that the other hand is free! ) to squeeze a likely key closed, which stops the hiss. Hence diagnosis.
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Author: Chris P
Date: 2006-02-25 10:31
As I generally use cork pads (and never skin pads) I find the suction test is the best one for these.
It's not the cork pads that are at fault in the majority of cases - it's most likely the tonehole bedplaces that have imperfections (natural vessels running through the wood, or chips) in them causing leaks.
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Author: Dan Shusta
Date: 2006-02-27 01:26
Gordon (NZ) wrote:
"For detecting leaks, I don't suck or blow.
I gently SQUIRT out a MOUTHFUL of air. By doing this I can accurately detect just how MUCH air is leaking while I maintain low pressure."
Interestingly, this method brought back a lot of memories. I used the same technique several years ago and found it to be very accurate. Perhaps you also closed off your lung air supply by having the back of your tongue arched till it closed the passage way? That is what I did so that I could easily detect if the pressure in my mouth was decreasing by my cheeks moving inward to maintain a constant "feel" pressure.
In my experiments, I found finger pressure on open holes to be of poor sealing quality and used neoprene plugs instead. I believe I purchased these plugs through Ferree's Tools. For me, the neoprene plugs increased the accuracy of the test.
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Author: Gordon (NZ)
Date: 2006-02-27 12:33
Yes, air easily leaks along fingerprint grooves, across open holes, especially if one's skin is fairly hard. Wetting the fingers helps.
Interestingly most flute players have their heads in the sand over this issue. When a customer wants very light finger pressure to seal on an open hole flute, I know he is crazy, unless he/she has very soft, moist skin.
For me, a very good reason to have traded my open hole flute for a closed hole one.
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Author: tictactux ★2017
Date: 2006-02-27 12:52
Gordon,
now I wonder why hand balm isn't on the geeks' shelves yet. Should, however, be something that doesn't interact with wood, silver or nickel.
--
Ben
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