Hi All,  As an addition to Eliyahu Shahar's posting yesterday,
I suggest one more step.

After all of the preparation work is done and you place the cloth
on the glued surface, pull the cloth back off the glued surface
immediately and inspect the cloth.  What you are looking for are
any voids where the glue has not been transferred to the cloth.
(Naturally, this assumes that you are working on a very flat surface
or workbench.  I use a piece of 1/2" thick plate glass, placed on top
of my workbench.)

If the contact area is 100% covered with glue, apply another thin
coating of glue and place the cloth back on the wood.  However, if
there are voids (which indicate a low spot on the wood) apply a second
coating of glue to the entire area and test it again.  Continue doing
this until you are certain that there is 100% coverage on the glued
surface.

Lastly, I only use tacks or staples (from a staple gun) if they were
used originally.  (They are always used in rotary pumps.)  If tacks were
not used originally, I use a cinder block as a weight, and place it on
the side opposite to the side being glued.  Most often, the weight has
to be applied for a period of time that is less than twenty minutes
before proceeding to the next side of the bellow.  However, the tricky
part is the overlap at the back of the bellows.  In most cases, tacks
were used to hold the cloth 'down' while the glue 'set'.

When I glue that portion of the bellow, I collapse the bellow about
95%-98% with "C" clamps before I start.  This creates a relatively flat
surface or working area.  Then, once the area has been tested for 100%
coverage, the final coating of glue is applied and the cloth gets
tacked in place.  But it doesn't stop there.  As a final step, I still
weight the glued surface with a cinder block.  This can be a little
tricky because you have to place the block in such a manner that it
will not fall off.

It's somewhat like balancing a heavy object on a thin pole.  You have
to set it in just the right place.  In extreme cases where the bellow
cannot be collapsed enough to create a relatively flat surface, I
place a sponge or sponge rubber between the weight and the bellow so
that pressure is applied as equally as possible on the glued surface.

In closing, all of this might seem a little extreme.  And in most cases
it's probably not necessary.  However, I really hate doing things
twice.  So I take these extra steps to insure that I only have to do
the job once!  As my grandpappy once said, "An ounce of prevention is
would a pound of cure."

Musically,

John A. Tuttle
Player-Care.com
Brick, NJ, USA