Masking tape for leak detection?

[Martin]

I'm not really sure whether this is such a great idea or not. What does everyone else think?

When I suspect a pad might be a leaker, I close the suspect tone hole with a bit of masking tape under the pad (sticky side to the tone hole...not against the pad), then play the instrument. Obviously any notes that require the taped up tone hole to open won't work.

If it plays any better, then I know that pad was indeed leaking...if it makes no differrence, then I know that pad was not the problem.

Sounds like a great idea? I thought so too...but I still haven't managed to find the leak(s) on my old clarinet since I stripped it down and repaded it...so perhaps it's not really a good technique after all.

Oh well, I'll throw my clarinet in the corner for a few more months until I come up with another cunning plan.

Cheers,
Martin

 

[kevgermany]

I'm no expert, but I don't see how this can work. All you're going is raising the height of the tone hole by the same amount all round.

And you're looking for small gaps - the sort of thing you'll detect with cigarette papers. Or a light.

 

[Pete Thomas]

I think he means the tone hole is sealed by the tape, so any leak that was there with the pad will not be there now. Yes this would work, is basically the same as testing for a leak by pressing down really hard on the keycup. (How some techs "repair" a leak!)

 

[AlanU]

There are no cunning plans. The instrument either seals or it doesn't.
You are also depositing adhesive on the tone holes.

As you are at this stage I suggest you find a friendly local repairer.
Hope it turns out fine.

 

[griff136]

I understand where you are coming from. for clarinets you can buy rubber plugs to block the toneholes. ( i personally dont use them). You are IMHO far better off getting a decent bright leak light and use it in a dark room to detect leaks. I use this method in the first intance followed by a feeler - cigarette paper cut to a point - to test for equal pressure between the circumference of the pad and the tonehole.

 

[AlanU]

As an afterthought, if you did want to seal a tone hole, why not try cling-film?
Not as sticky.

 

[Stephen Howard]

I think masking tape will be either too porous or too rough to provide a decent seal.
If you want to use this method you'd be better off using squares of Blu-Tack.
Thin them out a little then slide under the key - press down gently on the pad and the mastic will seal the hole. You shouldn't have to press too hard, you don't want to force the stuff into the tone hole as it might be tricky to remove it afterwards.

Hard-to-find leaks on a clarinet can sometimes be caused by leakage around the speaker key tube, the thumb key tube and sometimes where the thumb rest mounting screws have been driven through the bore. Such leaks can be temporarily sealed with cork grease or wax.
Cracks and splits may also be an issue.

As a last resort, assuming neither a cigarette paper test or a leak light showed anything, you could smoke test the joints. This involves blowing cigarette smoke down the joints, sealing up the ends and pressing all the keys down. It makes the instrument stink and the pads sticky, so there will be a lot of cleaning up to do - and I would only recommend it when all other testing techniques have failed.

Regards,

 

[Pete Thomas]

As a last resort, assuming neither a cigarette paper test or a leak light showed anything, you could smoke test the joints. This involves blowing cigarette smoke down the joints, sealing up the ends and pressing all the keys down. It makes the instrument stink and the pads sticky, so there will be a lot of cleaning up to do - and I would only recommend it when all other testing techniques have failed.

The next book: "Extreme Saxophone Repair"

It's odd that in this day and age, there only two commonly used leak detection methods are far from perfect. Leak lights don't show some leaks, cigarette papers have to be faffed around with trying in different positions. and the amount of "give" or pessure on the keycup still requires a fair degree of expert knowledeg/intuition.

I mean with innertubes, lilos etc, a small gob of spit or detergent shows up a very teeny leak that is obvious to the layperson, it would be useful if there was some kind of foolproof leakometer. (That didn't involve carcinogens)

 

[Stephen Howard]

There is!

You can buy a leak detector that works on a vacuum/pressure principle, but they're pretty expensive.

http://www.musicmedic.com/catalog/products/tool-m300.html

I'm not entirely convinced they're all that necessary either - it's a bit like having an expensive meter to tell you how clean your windows are.

Regards,

 

[Pete Thomas]

There is!

You can buy a leak detector that works on a vacuum/pressure principle, but they're pretty expensive.

Yes, but that only shows you that the instrument is leaking or not. It doesn't appear it would show you where the leak is.

 

[Stephen Howard]

Some of them do, they come with a collection of bungs that can be used to seal off specific areas.

Not sure if such attachments are available for sax and clarinet though - in which case, yes, it would only tell you that you have a leak...and not where.

Regards,

 

[Pete Thomas]

Some of them do, they come with a collection of bungs that can be used to seal off specific areas.

I was also thinking of the tricky ones to detect, such as tenon or bow which a leak light or fag paper won't reveal. But I guess if the pads are OK< and you sealed off the bell with something (tennis ball? Large rodent?), then some gob or detergent on those areas would actually show a leak.

 

[Stephen Howard]

The problem with that method is that the air pressure required to form visible bubbles will probably be enough to force keys open.
When doing a smoke test the amount of pressure used is very small indeed, hardly more than a breath.
Also, you might be hard put to see any small bubbles while you have the instrument in your mouth - and you'd have to drench the entire instrument in detergent, keys and all.

Regards,

 

[AdamBradley]

I wonder whether you can't get coloured inert gasses that would do the same job without being so ... Yucky?

 

[Stephen Howard]

I wonder whether you can't get coloured inert gasses that would do the same job without being so ... Yucky?

It would be an interesting idea, and perhaps quite useful. I'm sure such gases exist, though I doubt they're breathable - but it would be possible to use a pump to duplicate the required air pressure ( even a hand-held bladder would be good enough ) and use this to inject the gas.

Regards,

 

[kevgermany]

Chlorine's a nice yellowy/green colour, but it's hardly inert. Would sterilise the sax nicely, though.

 

[AdamBradley]

Would chlorine not potentially do something to the leather pads?

I shall ask sone chemical boffins where I work about the possibilty of getting an obviously visible gas which wouldn't have any naff after effects.

 

[Pete Thomas]

Chlorine's a nice yellowy/green colour, but it's hardly inert. Would sterilise the sax nicely, though.

Maybe mustard gas? Methane?

Or how about a leak seeking liquid that you just fill the horn up with?

 

[AdamBradley]

http://www.tapestockonline.com/spefsmsp.html

Whole load of similar stuff from special effects companies, theatre prop production folks etc. Most require some form of burning though, but that spray seems to be in the right direction.

Whether such a thing would muck up the inside of a sax any less than cigarette smoke, only trying it would find out. I wouldn't suggest spraying it straight into the sax but perhaps into a container from which you can pump it gently in controlled amounts. You'd want a light turbulent flow (a la breathing down it) as opposed to the laminar flow you'd get out the end of a nozzle.

 

[kevgermany]

Methane's clear & colourless, but I like the idea of mustard gas.

Maybe you have contacts in the special effects dept at the BBC Pete? They're sure to have something that'd do the trick safely.