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View Full Version : Tips for preventing bleedthrough on veneer?



ed mirzay
06-24-2006, 1:38 PM
Does anyone have any suggestions for ways to prevent glue bleedthrough on thin, light colored veneers? I have tried Titebond 3 (and 2, which is a little lighter in color) as well as polyurethane glue. The problem is most evident on dyed white anegre and the batch I currently have is fairly thin.
This isn't a problem with contact cement but I am leery of CC's ability to hold up over the long term for marquetry projects. None of the woods I am using are paperbacked as it is difficult to find a very wide variety of woods in that format and difficult to buy them in small quantities.
Any suggestions will be greatly appreciated!

Mitchell Andrus
06-24-2006, 2:34 PM
I seal the sheet first. If you know the top coat and glue to be used, this will help and select accordingly... Spray shellac or laquer primer/sealer. Stay away from water based for obvious reasons.

As always, test first.

Mitch

Jim Tobias
06-24-2006, 10:32 PM
Ed,
I have started using a "blocker" that is sold by Unibond. I use their unibond 800 (assorted colors) and the blocker has cut down on the bleed through significantly. Check it out at
http://www.vacupress.com/veneerglue.htm
Scroll to bottom of page for blocker.

Jim

Dave Fifield
06-24-2006, 11:19 PM
How much pressure are you using when you do a glue up Ed? I use a large homebuilt veneer press for my marquetry pictures that has four big screws that apply immense amounts of pressure. I have not had any glue bleed through issues yet.

The only treatment I do to the back (glue side) is to seal the joints between the venners with a slurry of Titebond III and wood dust, applied with a finger (to work it into the gaps nicely) and then scraped off with a plastic knife edge. Occasionally, I may work a little of this slurry into the back of ultra-thin veneers to partially fill the grain, but I try to keep the work as "dry" as possible to prevent warpage (which will open up gaps and ruin the work). For the whole of this operation, the front of the veneers are taped up to prevent glue leaking from the joints and to keep the picture together. I use 6" wide laser tape for this, others use veneer tape or parcel tape (the stuff you have to wet yourself). Then I shove the veneer between two pieces of wax paper, followed by a thick layer of clean paper and then press it (not too hard) for a few hours to keep it flat while the glue/wood slurry dries. Then, I apply glue to the substrate that I'm going to stick the veneers to (no glue on the back of the veneer required), spread it evenly with a roller, wait for it to just begin to get tacky, then place the veneer on it and press it - hard this time - overnight. I usually veneer both the back and front of my pictures at the same time. Works like a charm every time.

On the couple of occasions where I have had glue seep through to the front of the picture, it comes through the joints between the veneers, not through the grain itself. In all cases, the glue was successfully removed using a light scraping.

All I can think of is that you are maybe using too much glue and/or applying too much pressure.

Dave F.

Shaddy Dedmore
06-24-2006, 11:26 PM
Can you buy the veneer that has an adhesive already on the back?

Maybe post this Q over on the woodowrking side of the crrek to get more responses.

Shaddy

Dave Fifield
06-25-2006, 10:22 PM
I don't know of any pre-glued veneer for sale anywhere Shaddy. I'd be interested if there was though.

Hey, I just had another thought Ed. Have you tried those heat-activated glue sheets? You place a glue sheet between the substrate and the veneer and then iron (ordinary clothes iron) over it to activate the glue. My guess would be that you wouldn't be able to apply enough pressure with an iron to force the glue up through the grain. I don't know of a source for the glue sheets though, sorry. I heard that they are popular in the UK....maybe there's a source there.....anyone know?

Dave F.

Shaddy Dedmore
06-26-2006, 1:43 AM
Here's some at Rockler (http://www.rockler.com/product.cfm?Offerings_ID=2213&TabSelect=Details&SearchHandle=DADBDADBDADADDDGDDDAGFDADEGGDCGFCNDHG FDADHCNDEDIGFGGCNDJDJDADICNGDDADBGGDIGFDFDBDDGCDBG GDADADADBDADADADADGHGGFGOGFGFHCDADADADEDADADADADAD ADADBDFDADADADBDADADADADADADADADADADADADBDADADADAD GHGGFGOGFGFHCDADADADBDB), called Pressure Sensitive Veneer. Really weird looking link, so you might have to look it up manually from Rockler.com

Shaddy

Lee DeRaud
06-26-2006, 3:04 AM
Here's some at Rockler (http://www.rockler.com/product.cfm?Offerings_ID=2213&TabSelect=Details&SearchHandle=DADBDADBDADADDDGDDDAGFDADEGGDCGFCNDHG FDADHCNDEDIGFGGCNDJDJDADICNGDDADBGGDIGFDFDBDDGCDBG GDADADADBDADADADADGHGGFGOGFGFHCDADADADEDADADADADAD ADADBDFDADADADBDADADADADADADADADADADADADBDADADADAD GHGGFGOGFGFHCDADADADBDB), called Pressure Sensitive Veneer. Really weird looking link, so you might have to look it up manually from Rockler.comI've used a ton of that stuff over the years: once it's rolled down hard, it really stays stuck. Only problem is a somewhat limited variety of species available.

The adhesive used for it is available from 3M, but it requires some specialized equipment to handle it. Do a search in this forum for "adhesive", there was a discussion of it sometime last year....ah, here it is: http://www.sawmillcreek.org/showthread.php?t=25859&highlight=adhesive

ed mirzay
06-26-2006, 12:28 PM
My main hesitation with that would be the fear of failed joints over the span of a few years. Does anyone have any experience with the long term viability of an adhesive like this?



I don't know of any pre-glued veneer for sale anywhere Shaddy. I'd be interested if there was though.

Hey, I just had another thought Ed. Have you tried those heat-activated glue sheets? You place a glue sheet between the substrate and the veneer and then iron (ordinary clothes iron) over it to activate the glue. My guess would be that you wouldn't be able to apply enough pressure with an iron to force the glue up through the grain. I don't know of a source for the glue sheets though, sorry. I heard that they are popular in the UK....maybe there's a source there.....anyone know?

Dave F.

ed mirzay
06-26-2006, 12:33 PM
Don't laugh but as I have just started this project I haven't built a press yet, I jacked up the rear of my truck and set a sandwich of MDF, plywood, cork and the marquetry in the middle under the tire. I started with pieces nearly 5"x5" and on up to 12" x 12" and I had enough pressure for the 12"x12" so I had a lot of pressure on the smaller pieces. Again, the only wood this has really been a problem on has been the dyed white anegre. I may be a little liberal with the glue as well, I am going to try and scrape a smaller coating of glue on the next few projects and see if it work any better.
I am currently designing a mechanical veneer press to replace the truck as my primary means of assembly!


How much pressure are you using when you do a glue up Ed? I use a large homebuilt veneer press for my marquetry pictures that has four big screws that apply immense amounts of pressure. I have not had any glue bleed through issues yet.


Dave F.

Brent Vander Weil
06-26-2006, 1:09 PM
Ed-

Now you know you have to post a picture of that pressing technique... it is truly something that should be recorded for future generations as a testament to the ingenuity of man!!! I love it and may use it...

Dave Jones
06-26-2006, 1:16 PM
Ed, I've been using 3M adhesive sheets to hold .050" aluminum name plates on the front of machines I build. They've been holding for 15 years so far and no reports of any of them falling off (out of thousands shipped). In fact you pretty much have to destroy the name tag to get it off once you've applied pressure and waited a couple of days.

Dennis Perry
06-26-2006, 1:36 PM
ed i would invest in a vacuum press, 12" X 12" or 144 sq inches a vacuum press will give lets say 14#s per sq in. or a total of about 2,000#s. i don't think one tire of a pickup truck will even come close. if your work was 24 X 36 or 864 sq in. the vacuum press will provide over 12,000#s overall.
http://www.sawmillcreek.org/attachment.php?attachmentid=35271&d=1143739308

Dennis

Dave Fifield
06-26-2006, 9:06 PM
Dennis et al,

I recall a discussion recently on SMC that found that the normal air pressure (14 lbs/sq. inch roughly) is waaay lower than the glue manufacturers' recommend - they say 100 lbs/sq. inch - I checked, it says that right on the side of my glue bottle.

Doesn't this mean that all vacuum bag veneering systems are fundamentally flawed and cannot be getting the best possible glue-up? Obviously, they work, or we wouldn't use them, but are veneer presses with large screws what's really needed to make the glue work best?

Inquiring minds want to know....

Dave F.

Mitchell Andrus
06-26-2006, 10:29 PM
Many commercial operations use heat and pressure. Usually a huge microwave oven is involved. Makes it quick and permanent.

Mitch

Dennis Perry
06-26-2006, 11:46 PM
Dave,
100#s per sq.in. then one sq ft (144*100=14,400) would then require a press that can do 14,400#per sq.in. or a 1x12 glued up then would require 1,200#s ? I knew if i posted that it would start something. Anyway Dave your latest work is great.

Dennis