I'm about to fire up my new vacuum press for the first time and was
wondering what the consensus is concerning platens. I read on Woodweb
that you only need a grooved platen on the bottom while other places
(joewoodworker.com) indicate that you need grooved platens top and
bottom. Also do the grooves on that bottom platten face toward or away
from the bag?

Thanks, Damian

On 1 May 2007 09:58:34 -0700, damian penney wrote:
I'm about to fire up my new vacuum press for the first time and was
wondering what the consensus is concerning platens. I read on Woodweb
that you only need a grooved platen on the bottom while other places
(joewoodworker.com) indicate that you need grooved platens top and
bottom. Also do the grooves on that bottom platten face toward or away
from the bag?

I use grooved plattens top and bottom for flat work. The grooves always
face away from the bag.

For work that is not flat, I use a form that is flat on the bottom, and
place a grooved platten under it. On top, I use a non-grooved platten of
thin bending plywood (or ordinary 1/4-inch plywood if the curve is
gentle enough to use that). Between the bag and that platen, I place
plastic evacuation mesh sold for the purpose:

http://www.vacupress.com/accessories.htm#evacunet

That mesh must be a little larger than the top platen, so there is no
air trapped on top of the work.

Remember to coat your platens with something that the glue you're using
will not adhere to. I've had good luck with paste wax. Plastic packing
tape should work well, too. Remember to keep the grooves clear.

--
Art Greenberg
artg at eclipse dot net

On May 1, 11:17 am, Art Greenberg wrote:
On 1 May 2007 09:58:34 -0700, damian penney wrote:

I'm about to fire up my new vacuum press for the first time and was
wondering what the consensus is concerning platens. I read on Woodweb
that you only need a grooved platen on the bottom while other places
(joewoodworker.com) indicate that you need grooved platens top and
bottom. Also do the grooves on that bottom platten face toward or away
from the bag?

I use grooved plattens top and bottom for flat work. The grooves always
face away from the bag.

For work that is not flat, I use a form that is flat on the bottom, and
place a grooved platten under it. On top, I use a non-grooved platten of
thin bending plywood (or ordinary 1/4-inch plywood if the curve is
gentle enough to use that). Between the bag and that platen, I place
plastic evacuation mesh sold for the purpose:

http://www.vacupress.com/accessories.htm#evacunet

That mesh must be a little larger than the top platen, so there is no
air trapped on top of the work.

Remember to coat your platens with something that the glue you're using
will not adhere to. I've had good luck with paste wax. Plastic packing
tape should work well, too. Remember to keep the grooves clear.

--
Art Greenberg
artg at eclipse dot net

Why do you place the grooves of the MDF platen away from the bag, but
the breather mesh, which does the same job as the grooves against the
bag?

I currently have a grooved mdf platen for the bottom, and then two
solid melamine platens to go above and below the veneer sandwich. Will
I need to coat the melamine with wax or will that be fine on its own?

On 1 May 2007 11:39:37 -0700, damian penney wrote:
Why do you place the grooves of the MDF platen away from the bag, but
the breather mesh, which does the same job as the grooves against the
bag?

The reason for the grooves is to allow air to flow from all points
inside the bag to the vacuum pump. If the grooves are facing the bag,
they could become blocked as the pressure inside the bag decreases. That
might trap air in some portion(s) of the bag, which in turn could
prevent you from having equal pressure across the work being glued.

The breather mesh is designed to prevent the bag from interfering with
air flow, so its OK to have it against the bag.

I currently have a grooved mdf platen for the bottom, and then two
solid melamine platens to go above and below the veneer sandwich. Will
I need to coat the melamine with wax or will that be fine on its own?

Melamine probably doesn't need any additional treatment.

--
Art Greenberg
artg at eclipse dot net

The breather mesh is designed to prevent the bag from interfering with
air flow, so its OK to have it against the bag.

Fair enough, that makes sense. Okay well wish me luck going to give it
a whirl as soon as I get home

Damian