Klarinet Archive - Posting 001052.txt from 2000/06

From: Christian Budde <budde@-----.de>
Subj: Re: [kl] Gortex pads
Date: Mon, 26 Jun 2000 07:24:49 -0400

On Fri, 23 Jun 2000, David B. Niethamer wrote:
> Gortex, according to my understanding, is supposedly a material that
> "breathes", ie allows air to pass through. So how can it create a good
> seal as a clarinet pad material?
>
> Each time this subject comes up, I ask this question. I have yet to get a
> satisfactory answer. Anything from the repair techs on the list?

Though not a repair-tech, perhaps I can give an answer: On the one hand,
"Seal" doesn't mean "to let absolutely nothing through" as a technical
term. A seal e.g. of a bearing only makes it difficult for a fluid (or
dirt) to get through. The same is true for the pads on a clarinet. They
must supply as much pressure-drop at the hole to make the amount of air
leaking through just very small.

On the other hand, Gore-tex is a thin PTFE (Teflon) foil with tiny (very
tiny) holes in it that don't let condensed fluids (rain) through but allow
humidity (uncondensed phase) to pass through. This is because the size of
the holes is only a few times larger than the water-molecules. One must
think of it more like an osmotic membrane, that is, the transport is
induced by a difference in concentration on both sides of the membrane and
diffusive transport rather than pressure drop. Although I never tried, You
will presumably not be able to blow air through a gore-tex membrane.

HTH,
Christian

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