Darryl Keil Last Activity 2025-02-12 2:48 PM
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Dave Shaw

Posts: 37

Joined: 2005-11-06
Location: Arizona

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Subject : Pressing multiple panels at once.
Posted : 2006-05-16 4:44 PM
Post #33055
I'm teaching a small class on decorative veneering with everyone doing a 16" x 16" panel. These have a walnut burl center, stringing and a 45 degree border (different thickness of veneers and stringing) on one side and a maple backer veneer on the other side. To further complicate this, the walnut burl has lots of very small bark inclusions (holes) and the 45 degree border is beech. I'll be dyeing (transtint dye) some glue pretty dark to take care of the burl. Here is the plan: mix up 2 batches of Unibond 800, making one dark and one light. Put the light colored glue on the core completely covering it, and put a wiped off coat of the dark glue on just the walnut burl to fill the small holes, that way (I hope) the light colored glue will not show thur the walnut.

I don't want to haul my 4' x 10' bag out of my shop, so I'll use my smaller 4' x 4' bag to press these panels.

The question is: can I make one stack and press all 4 of these panels at once ? They will have Plattens on top and bottom, heavy canvas and plastic sheets and a seperating platten between each panel. The glue will be Unibond 800.

Any suggestions will be appreciated.

Thanks,

Dave - with a bullet hole in my foot -- well I didn't want to make it too easy!


 
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Darryl Keil

Posts: 1454

Joined: 2003-05-22
Location: Maine

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Subject : RE: Pressing multiple panels at once.
Posted : 2006-05-17 8:13 PM
Post #33056 - In reply to #33055
Dave,

Im not sure how the two colors of Unibond 800 will work, but you can definitely stack 4 panels on top of each other the way you described. I have done it many times myself.

Sincerely
Darryl Keil


 
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Dave Shaw

Posts: 37

Joined: 2005-11-06
Location: Arizona

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Subject : RE: Pressing multiple panels at once.
Posted : 2006-05-17 9:52 PM
Post #33057 - In reply to #33056
I'd better try the 2 glue color technique before I inflict in on the class. I'm curious as to how others glue up panels the have very dark veneers and very light veneers on them and not have the bleed thru mess up one of the veneer colors?

Can I get by with 1/8" MDF cauls between the panels or do I need something thicker?

Thanks,

Dave


 
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Darryl Keil

Posts: 1454

Joined: 2003-05-22
Location: Maine

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Subject : RE: Pressing multiple panels at once.
Posted : 2006-05-18 3:51 PM
Post #33058 - In reply to #33057
Dave,

1/8" cauls between panels are fine.

As far as the glue color goes I would just use dark catalyst for the entire panel. The color of the glue only relates to open pored wood as it will fill these little holes. If its darker than the veneer it wont stand out very much but if the veneer is dark and the pores are filled with light colored glue that will jump out at you.


 
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Dave Shaw

Posts: 37

Joined: 2005-11-06
Location: Arizona

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Subject : RE: Pressing multiple panels at once.
Posted : 2006-05-22 5:43 PM
Post #33062 - In reply to #33058
This effort didn't turn out well. When we started to take the tape off the pressed panels with water, the panels bubbled to varying degrees on 3 of the 4 panels. I took the worst panel apart and found that there was good glue coverage on the substrate but none on the bubbled parts of the veneer. The panel backs were OK for the most part - no bubbles. The fancy faces were made up of a walnut burl center, a beech border and black stringing between them. The stringing is about .032" thick and the border and center are about .022 thick. The glue was unibond 800 8 oz, dark catalyst 0.8 oz, blocker 0.8 oz and a 1/8 tsp of Transtint dye. The glue was fresh ie still low viscosity. Both sides of the panel were covered with 4 mil plastic and 12 oz canvas and 1/8" MDF caul.

The process, start to finish, of getting 4 panels ready and in the press was about 30 minutes.

It looks to me like there was not enough pressure to compress the canvas to get a good press.

I used the aboue glue and pressing on a single panel and it worked fine.

Anyone have any ideas about what might have gone wrong? I can't do this again - the embarassment is extreme. YIKES!!

Dave



 
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Darryl Keil

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Location: Maine

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Subject : RE: Pressing multiple panels at once.
Posted : 2006-05-22 8:53 PM
Post #33064 - In reply to #33062
Dave,

Sorry you had poor success with your multiple panel pressing. I'm not clear what the problem was except for the possibility of different veneer thicknesses, and I have never used canvas to deal with it. At least that's what I assume the canvas was used for.

I just finished teaching a class last month where we multiple stacked quite a lot of panels with almost no problems. We did not have any veneer thickness variations and only used 1/4" cauls with plastic as separators between panels.

I have always used 1/32" or 1/16" rubber sheeting for uneven veneer pressing. I wonder if this would have worked any better than the canvas.

Sincerely
Darryl Keil


 
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Dave Shaw

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Location: Arizona

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Subject : RE: Pressing multiple panels at once.
Posted : 2006-05-22 9:55 PM
Post #33065 - In reply to #33064
I have pressed 4 checker boards in one stack with differences in veneer thickness, used heavy canvas to take up the differences and they came out perfect. I used the same glue etc. What puzzles me is that the veneer that is coming up shows no trace of glue on the back of the veneer but plenty on the substrate directly below. So it looks like the veneer never got pressed into the glue line. The gage on the pump was at 23" hg so that should have been plenty of pressure. I think since the backs were pretty much OK (no stringng) it must have been the thick stringing that caused the problem. On the other hand, I've pressed alot of panels with the same stringing w/o any problems. Hummm.

Where do you get the 1/16" rubber sheeting? What do others use to take up thickness differences?

Thanks,

Dave



 
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Darryl Keil

Posts: 1454

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Subject : RE: Pressing multiple panels at once.
Posted : 2006-05-24 9:39 AM
Post #33068 - In reply to #33065
Dave,

You can get natural rubber from a rubber supply house which any medium to large city will usually have. Natural rubber which is beige in color is a bit softer than the more common black rubber. I recommend the natural rubber over the black neoprene one.

Sincerely
Darryl Keil


 
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Dave Shaw

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Subject : RE: Pressing multiple panels at once.
Posted : 2006-05-24 11:28 AM
Post #33070 - In reply to #33068
Found a source for natural rubber sheeting. Try this site. http://www.rubbercal.com/Pure_Gum.html

The price is not too bad at $3.62/ft for a whole 50' roll, 36" wide. Also available in 48" width. The stuff I looked at is 1/16" thick. Other thicknesses are available.

Dave


 
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Don Stephan

Posts: 825

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

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Subject : RE: Pressing multiple panels at once.
Posted : 2006-05-24 9:32 PM
Post #33071 - In reply to #33070
When you included the .032 stringing with no problem, was there a caul above the canvas, or just the vacuum bag? If I understood your sandwich description, there were multiple layers of backer/substrate/face/canvas/caul. As the stringing was about .01" thicker than the rest of the face veneer, the canvas would have had to compress at least .011" over the stringing before the caul could have applied any pressure (through the canvas) onto the face veneer. My first thought when pressing face veneer of differing thicknesses would be to use the canvas without a top caul, so that the flexible vacuum bag could apply pressure to the canvas over the thinner veneers. Perhaps I misunderstand the use of canvas/rubber over mixed veneers?


 
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Dave Shaw

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Location: Arizona

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Subject : RE: Pressing multiple panels at once.
Posted : 2006-05-25 2:10 PM
Post #33073 - In reply to #33071
Yes, there was a 1/2" caul above the canvas. The canvas is .033" thick. I don't understand how not having a caul on the top would help any of the 3 panels below it. This is a stack of 4 panels. I also pressed a single panel with the canvas and cauls and it pressed fine. Thanks for the input. Dave


 
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Don Stephan

Posts: 825

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

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Subject : RE: Pressing multiple panels at once.
Posted : 2006-05-26 7:59 PM
Post #33075 - In reply to #33073
Sorry for not explaining better. I was wondering if the top panel, if it had canvas above but NOT a caul, would have worked better because the lack of caul allowed the canvas to adjust better to the different veneer thicknesses. Since you did have a caul over the top panel, I am clueless.


 
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Earl

Posts: 75

Joined: 2003-12-04
Location: Pensacola FL

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Subject : RE: Pressing multiple panels at once.
Posted : 2006-05-27 10:25 AM
Post #33077 - In reply to #33062
Dave,
Several thoughts. If you had laid out your tops on one sheet you would have had much more overall pressure applied. A 32"x32" panel would have approx. 4 times the pressure applied versus your 16"x16".

I never read what substrate you used, sometimes ply is not even flat and mdf if cut and set aside for days or weeks can swell marginally at the edges (were talking thousandths)

The rubber works, but it doesn't, IMHO, get the veneer as flat as a caul. Takes more sanding to flatten the panel.

Hope you have better luck with the next batch.
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