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 Testing for leaks
Author: Plonk 
Date:   2010-07-14 10:16

Is there a beginners guide anywhere?

What's the easiest way for a non-techie person to test at home with no special equipment?

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 Re: Testing for leaks
Author: Chris P 
Date:   2010-07-14 10:45

With the top joint only, seal the middle tenon with any finger of your right hand (lick your finger to make it seal better), then close the finger and thumb holes with your left fingers (also lick these fingers to make a good seal on the toneholes) and suck the air out from the top tenon and then stop once a vacuum has been created. This vacuum should hold for several seconds - the longer the better.

Do the same with the lower joint, but this time closing the fingerholes and E/B key with your right hand fingers while sealing the lower tenon with the palm of your left hand and suck the air out from the middle socket to create a vacuum.

Chris.

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 Re: Testing for leaks
Author: Plonk 
Date:   2010-07-14 11:12

Thanks!

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 Re: Testing for leaks
Author: Jack Kissinger 
Date:   2010-07-14 13:18

Use the search function for "suck blow test" without the quotes. You will find considerable discussion of Chris' approach (including some limitations) as well as alternatives.

Best regards,
jnk

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 Re: Testing for leaks
Author: tictactux 2017
Date:   2010-07-14 17:01

Jack Kissinger wrote:

> Use the search function for "suck blow test"

IOW, if you can blow, it sucks. [tongue]

IME a suck test doesn't reveal all that much (except that if sucking doesn't cut it, you got a major league leak).
As the normal m.o. is blowing, make sure that no pads pop open and no air escapes while you blow reasonably hard (better just squirt some air out of your cheek pockets rather than blow with all your lung capacity).

My teacher gave me this hint: put a party balloon over the lower tenon, close the holes as if you were playing, then carefully inflate the balloon. Not only does this help you determine the right amount of finger pressure, it also is a poor musician's lung trainer (with the clarinet fully assembled, but with the balloon in lieu of the bell).
And you have plenty time to locate the culprit pad when the balloon tries to contract. (your own blowing noise will distract you from the sound the escaping air makes).

--
Ben

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 Re: Testing for leaks
Author: Caroline Smale 
Date:   2010-07-14 18:44

Using the vacuum test method discussed above it's evaluation is much more effective if you only slowly create a light vaccum.
Sucking too hard and quick can draw down the skin of a mediocre sealing pad hard onto the seating giving a false impression of airtightness.
Just experiment with varying degrees of vaccum - that in itself can tell you quite a lot about the airtightness of the instrument.

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 Re: Testing for leaks
Author: David Spiegelthal 2017
Date:   2010-07-14 19:50

Give the instrument to my oboist friend E _ _ _ _, she has such a light touch on the keys she can 'find' a leak on any woodwind instrument, even one that I would swear in court is sealing perfectly.

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 Re: Testing for leaks
Author: Gordon (NZ) 
Date:   2010-07-16 08:59

You need a lot of blow to blow up a balloon. That,to me, is far too much blow for detecting leaks. There is nowhere near that pressure inside a clarinet during normal playing.

For a blow test, the idea IMO is to block the back of the throat with the tongue, then use the rest of the tongue to push a small quantity (say 1/4 - 1/2 a mouthful) of air GENTLY into the section of clarinet. It is by doing this that one can easily detect how quickly the air is escaping, by how much the tongue has to travel, pushing the air out of the mouth, in order to maintain pressure.

As for sucking versus blowing... Imagine a damp bed of sand, and how much easier it is to suck air through it than it is to blow air through it. The very slight porosity of the timber and pad membrane, IMO, makes it act a bit like a bed of sand. So I think sucking is a rather unreliable test, especially if that draws the pad membrane to making a seal, as somebody has already mentioned.

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 Re: Testing for leaks
Author: Plonk 
Date:   2010-07-16 09:08

Thanks for all the responses - it seems logical to me that blowing would work better than sucking, but I am just a novice!

Another question: I blocked up the end of the bell with a thick towel (don't ask why!) covered all the holes and blew, and I got some really high harmonics. This surprised me, as I expected that I wouldn't get anything at all. I didn't check what the notes were, but with my embouchure I was able to play about 4 or 5 tones e.g. C, D, E F or something like that.

Is this normal, or does it indicate there is a leak? If it's normal, where is the sound coming from?

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 Re: Testing for leaks
Author: Megham 
Date:   2010-07-16 18:28

In my experience this is normal. Your experiment is very similar to an exercise in overtones Dr. Spring at ASU showed me. The only difference was that he uses a cork to plug the bell and I think he also would do it chromatically from low E to Low G. Don't quote me on that though. He would move his tongue to get different overtones. You can also do the exercise without a cork starting at open G and going down chromatically. You should be able to get three overtones per note. It is a great exercise for helping you understand how the tongue's position affects the notes you are trying to play. As for where the sound is coming from, I don't have a clue.

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