In 990709 MMDigest Rod Cornelius asked:

> Can you help with an inquiry from a friend of mine who is restoring
> a Wilhelm Bruder fairground organ, 62 keyless: what should he use
> to surface the main chest under the pallets?

The normal surface treatment for the underside of any wind chest
receiving pipe valves is just the wood itself, well machined.

> There was a thin cardboard there before, but damaged.  He re-lined
> with a similar cardboard, but it is leaking air from some pallets and
> has to be redone.

I would be very fearful of using any kind of cardboard to have the pipe
valves seat upon them, especially glue-sized, for two reasons:

1)  The glue size on the surface would tend to become sticky in hot
or humid weather; thereby not allowing the valves to work at all!

2)  A very smooth surface (such as lacquered or glue-sized) tends to
have less "surface tension" and pressurized air has a way of seeping
across the surface.  Most valves have an oversize of only 1/8" maximum,
so it is important they have something to seat against solidly that is
smooth and virtually perfect.  No cracks or chips around the hole edges
allowed!

> He used hot glue and he glued the cardboard and let it dry before
> he glued it into position.

It's not clear from this description if the glue-size is on the side
facing the valves or on the middle between the existing board and the
cardboard itself (using the hot glue like contact cement).

Another thing to check for is how much spring tension there is holding
the valves closed.  It may be that the springs have weakened, or else,
if not already done, the valve facings need to be re-done.

One trick that has helped me with seating new valves is the application
of talcum powder (not to be confused with Baby Powder!) to the valve
facings.  This tends to help prevent any sticking of the valves, as
well as slightly fills in the pores of the valve leather, thereby
allowing it to seat a bit better until the valve leather takes on a
compression of the hole.  Hope this information is helpful!

Faithfully,

Rich Schneider
(Professional Pipe Organ Builder)