Darryl Keil Last Activity 2025-09-09 11:09 AM
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jzee

Posts: 5

Joined: 2009-07-03

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Subject : platens and cauls
Posted : 2009-07-03 7:05 PM
Post #35591
New to vacuum pressing. Just got a compact100. I'd like to pick everyone's brains about platens and cauls. My typical projects are marquetry veneers applied to 1/4" MDF ranging in size (so far) from 3"x3" to 16"x20". I've also commonly applied the marquetry veneers to the seat tops of stools.

My main questions are:
1) Do the air flow grooves of platens and cauls face the bag or towards the work piece?
2) How far apart do you make the air flow grooves?
3) For the type of projects that I do, do i need both a top caul and a bottom caul that sits between the platen and the work piece?
4) If I use 1/4" MDF for cauls, do I need to put air flow grooves in them?
and if so, how deep and again do the grooves face away or towards the work piece?
and finally...
5) Do all of you use the recommendation included in the pamphlet sent with the vacuum pump to thread the vacuum hose tip into the platen to open at the work piece side of the platen which has the air flow grooves (grooves facing the work piece)?

Thanks from the "rookie".


 
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craig tufankjian

Posts: 308

Joined: 2004-02-01
Location: syracuse ny 13208

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Subject : RE: platens and cauls
Posted : 2009-07-03 7:36 PM
Post #35592 - In reply to #35591
jzee,

#1 air flow grooves are up and do not face the bag
#2 my spacing is 6x6, they can be wider, make sure the grooves penetrate the the inserts
#3 platen yes , should have one on the top of the work piece as well (why take chances?)
#4 you do not have to groove the cauls that are used on top of the work piece
#5 clueless


 
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jzee

Posts: 5

Joined: 2009-07-03

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Subject : RE: platens and cauls
Posted : 2009-07-03 8:15 PM
Post #35593 - In reply to #35592
craig,
Thanks for your reply. I'm new to this so let me ask you a few questions to clarify...
a) how do you keep the air flow grooves from marring the veneer if they are facing the work piece?
b) when you say the grooves should penetrate the inserts, what exactly do you mean?
c) are cauls simply flat smooth pieces (1/8 - 1/4" MDF) that are sandwiched between the veneer surfaces and the platens? I guess this would then protect the veneer surfaces from damage or marring from the air flow grooves.
d) if you use a heavy platen (3/4" MDF) on top of the work piece as well (your suggestion #3)is it grooved? and, if so,which way do the grooves face?
thanks again


 
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rwayne

Posts: 5

Joined: 2009-07-04
Location: Central Illinois

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Subject : RE: platens and cauls
Posted : 2009-07-04 8:21 AM
Post #35594 - In reply to #35593
jzee--
I just finished a week long class at the Marc Adams School about 2 weeks ago on Veneering. it was taught by Tal Seigman. I also am very new to this forum and to veneering. Like you I am just learning. Your question was one that was very close to what I had just emailed to Tal about so I thought I would chime in. What the school had for a platin was a sheet of melamine with grooves cut into it about 1/8" deep. in 5" square pattern. The melamine was used to prevent glue from sticking from any run out. I think that if you used plastic you would be able to use any other flat board for your platin. The order that Tal had us use in class to do the pressing was this We took a bottom caul placed a piece of plastic over it followed by the piece to be pressed( backer veneer,core and face veneer) then we placed another piece of plastic over that followed by a cotton cloth over the plastic then the top caul. We put a couple pieces of packing tape over the edges of the top and botton caul and then paced it in the vacuum bag for pressing. The top and bottom cauls were I think 3/4 ". I am not sure if there is a recommendation as far as the thickness of caul to be used. The cauls are not grooved just the platin.
I have taken 3 classes at the school in the past 2 years and there is one thing that all the instructers say-- is that they are teaching how they do it .they tell you there are other ways of doing the same thing which are just as good but that their method works for them.
I am waiting for Monday so I can call Darryl or someone and ask some question about their products.
I have been lurking on this forum for a couple weeks now but saw your post and decided to respond.
The people on this forum seem to have a lot of knowledge on veneering and I have enjoyed reading all the questions and responses.
Also your question about penetrting the insert I have no idea but would also like the know what was meant.
What I was taught I know is not the only way just one of many probably.
Hope this helps
rwayne


 
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Don Stephan

Posts: 825

Joined: 2003-07-18
Location: Cincinnati, Ohio

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Subject : RE: platens and cauls
Posted : 2009-07-04 6:08 PM
Post #35595 - In reply to #35594
The grooves in the platen are to provide a way for the air in the bag to reach the vacuum hose. They should run both the length and width of the platen. If they are 1/8" or so deep, less likely to be blocked by occasional drop of glue squeezeout. The grooves would mar the workpiece, so a bottom caul is placed on top of the platen. It should be at least as long and wide as the workpiece, but can be longer and wider. The bottom caul can be as thin as 1/4" as the platen is (or should be) very stiff and flat. Ideally the bottom caul is coated to keep glue from sticking, but you could alternatively wrap the workpiece with 4-6 mil plastic. If using sheet of plastic, BE SURE plastic does not fold back on itself or wrinkle on either side of the workpiece as the extra thickness will dent the surface of the workpiece.

If only veneering one side of the workpiece at a time, don't need a top caul. If veneering both at once, the top caul can be as thin as 1/4", again melamine or similar coating is an advantage. Top caul should extend about 1/8" beyond all four edges of the workpiece. If longer and/or wider, the vacuum will try to break off the overhang and/or flex the top caul.

If using multiple pieces of veneer (i.e. marquetry) on a surface, quite possible there will be differences in veneer thickness. A compressible pad is recommended in those cases to even out the pressure so all pieces of veneer tight against the substrate. Many people use single layer of thick canvas. I've used rubber roofing if I can avoid the seams in the roofing; several people have used a different type of rubber sheet - try a search on this forum to find description.

A couple videos on vacuum veneering are highly recommended - there is some overlap between the two but there are some unique explanations on each. One is available at www.vacupress.com, the other at www.schurchwoodworking.com. If interested in veneering curves, the 2nd at vacupress.com is recommended; if interested in marquetry the 2nd at schurchwoodworking is recommended (although I haven't seen it yet).

You're also welcome to download a compilation of tips, suggestions, explanations, et cetera that I've collected over the years. www.stephanwoodworking.com and at the bottom of the home page click "downloadable files that may be of interest to woodworkers." On that page click either form of the veneering notes.


 
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jzee

Posts: 5

Joined: 2009-07-03

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Subject : RE: platens and cauls
Posted : 2009-07-04 8:59 PM
Post #35596 - In reply to #35595
Don and rwayne,
Thank you for your answers to my questions. Its really cool how helpful people are here.

Don...sounds like only the platen needs to have grooves in it??? and the grooves are on the side facing up towards the rest of the stack including bottom caul and work piece?
Do you have the bag end of the vacuum tube actually inserted thru the bottom platen to open on the upper surface with the grooves? and the grid of grooves would include grooves intersecting with the hole that the vacuum tube is threaded thru?

thanks for any further input.


 
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BigRob777

Posts: 142

Joined: 2008-05-26
Location: Newark, DE

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Subject : RE: platens and cauls
Posted : 2009-07-05 1:53 AM
Post #35597 - In reply to #35596
Jzee,
I think I finally understand what you mean by your last question. It sounds like your vacuum tube goes into the bag from the bottom. Is that right? Now I'm a real newbie to actually veneering, but could you be using your bag upside down? Just a thought. If I recall, Darryl shows in his video the tube coming into the bag from the top. I'll review his gotdy DVD again. Do you have his DVDs? They are really helping me to understand the process.
Rob


 
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Brad

Posts: 87

Joined: 2008-04-22

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Subject : RE: platens and cauls
Posted : 2009-07-06 1:39 PM
Post #35600 - In reply to #35597
I will echo Don's comment that you need Darry's DVD's. I suggest all three. I recall there was a deal when you buy them all. Veneering opens up a lot of options. My original plan was only to make door staves, but now everytime I order veneers I seem to end up with something new to try.

I have found the nicest caul material is that 1/8" shower board (I dont recall its proper name), but its not the cheapest by any stretch. Many times I use 1/4" hardboard. Its a bit cheaper and glue does not stick to the one side so long as you do not damage the surface. Veneering in a vacuum is a bit hard on caul material since the top caul cannot be much more than 1/8" larger than your work piece.

Most of the time I use a caul top and bottom. I use shrink wrap to tie it all together. I find this make it easier to handle and if you bump something accidentally it will protect that piece you have worked long and hard to create.

Good luck


 
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Don Stephan

Posts: 825

Joined: 2003-07-18
Location: Cincinnati, Ohio

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Subject : RE: platens and cauls
Posted : 2009-07-05 4:41 PM
Post #35598 - In reply to #35596
Yes, the grooves are only in the platen, and only on the upper surface of the platen. The grooves are to allow air inside the bag reach the vacuum hose, a hole must be drilled at one of the intersections of lengthwise and widthwise grooves, that will line up with the nipple on the underside of the bag. The vacuum hose is inserted through the nipple into this platen hole. The end of the vacuum hose must be buried within the thickness of the platen and not extend above the bottom of the grooves. At a bare minimum, Darryl's 1st video is HIGHLY recommended.


 
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BigRob777

Posts: 142

Joined: 2008-05-26
Location: Newark, DE

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Subject : RE: platens and cauls
Posted : 2009-07-05 5:37 PM
Post #35599 - In reply to #35598
Ahh, I see where the difference comes in. Unfortunately, I didn't find this forum, until after I got my vacuum system. The assembly instructions for the Dura-Max bag says to center the single valve stem over a groove in the top platen. The two systems seem to be very different. There is no interior tube that goes into the bag in mine. I wondered why Darryl packed stuff into the platen, in his 2nd dvd (to simulate a jam). In my system, there is no drilled hole in the platen.

I really wish I had found this forum first. The Vacupress system sounds much better.

Rob
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