Removing Glue Bleed-Through on Veneer

      Try your trusty scraper. November 27, 2007

I am working on a project with a very open grain veneer. I have not used a veneer with this porous a grain before and anticipated some potential problems. I am using Titebond's Cold Press for Veneer type glue.

I did a sample piece prior to the finished piece and had bleed-through on the sample. I used less glue on my final pieces with better results, but still had a few small spots. A small pin-head size drop of glue smashes out to anywhere from 1/8 inch diameter to 1 inch diameter. Most of the spots on the final piece are less than 1/4 inch diameter. But there are probably 10 - 12 spots on about 8 square feet of veneer.

I sanded and urethaned the test piece and the glue marks show up pretty bad (larger spots). I don't want any of these spots showing on my final pieces. Can anyone advise on how to remove the glue from the surface of my veneer prior to urethane? Do I need to sand more aggressively? Or is there a product I can use to remove the glue from the surface without damaging the adhesion through the porous wood?
Forum Responses
(Veneer Forum)
From contributor R:
Thereís a product that could be applied on the back (glue side) of the veneer. I think itís called ďglue size.Ē Some of the woods are bound to have a bleed through anyway. I was making a table for someone in quarter-sawn Tamo and itís a see-through veneer. I would recommend a good glue spreader (roller). Apply only as much glue as needed. I donít mind Titebond cold press glue, but I donít find it very strong. Try something a bit gooier and less runny, such as Titebond type 3 or 2. Formaldehyde adhesive would be ideal. I also think sanding is not done properly. Many woodworkers are using too fine of a grit sandpaper from the very start and itís just clogging up and not really doing anything to a rubbery bleed through. Try starting with a 100 or even 80 to get rid of the glue and then go to 220. What kind of veneer are you using?

From the original questioner:
Thanks for the reply. The veneer I am using is Imbuya burl. The pieces are highly figured. Some areas are not prone to bleed-through, some are. There are some areas where you can see a little bit of light through the veneer.

But here's the deal. The veneer has already been glued and pressed. It is on. And now I have a few bleed-through spots with dried glue on the final product. Upon careful inspection, there are probably 40-50 small glue spots. Most of them are less than 1/8 inch diameter. Many are just pin-head size specks. But they are very noticeable when the light hits them at certain angles. So, my issue is beyond prevention at this point. Sizing and different glues are not options. (But I will definitely try something different in the future!) I am looking for options for removal of the glue spots that now exist.

I did sand the sample piece with 320 grit. I worked at it for a while, but the wood became very dusty and I couldn't see the glue spots, so I assumed they were gone. I cleaned and wiped down the sample piece and didn't notice the glue, but it became very noticeable when I applied the urethane. I have intentionally put a drop of glue on another scrap sample piece to see if I can remove. I guess I will try coarser sandpaper.

From contributor R:
320 grit will not remove the glue unless you have a very long time to complete the job. If I understand correctly, while you are pressing veneer in the vacuum or other type of press, some glue comes all the way through the veneer and forms a round spot on the surface. That can be removed by aggressive sanding. I would recommend using a high-quality orbital sender; itís just faster and much rougher grit. No fill sandpaper works good. Just donít tilt the sander while you are fighting the glue. Try to slide it evenly. Wipe down the surface with a moist rag to get rid of the dust. Glue will stay dark and glossy. You will see it under certain angles. You could also try solvents like alcohol or acetone for the same purpose. There are no solvents or solutions that would remove bleed but sanding. For Imbuya burl or any other burl, I would recommend formaldehyde type adhesive. All burls are very likely to start moving, checking, and cracking if yellow glue is used.

From the original questioner:
Thanks. I will try 100 followed by 220, then finish up with 320 on an orbital. I hope the burl doesn't shift. I have heard good things about using formaldehyde, but I have always had sufficient luck with Titebond's Cold Press for Veneer type glue. But it is done. So all I can do is cross my fingers.

From contributor M:
Here's one application where judicious use of a cabinet scraper (handheld - not in the #80 holder) really shines. It should make short work of the glue spots.

From contributor R:
Yep, I agree. Good scraper will do a marvelous job.

From contributor M:
It's hard to get by in my (1-man) shop without a scraper. My primary Bahco scraper is among the first tools brought out every day and is among the last things put away every evening. It has too many fast and efficient uses to be ignored.

From the original questioner:
Thanks for hitting me over the head with the obvious! Luckily, I didn't sand it yet. I think the sanding is deceptive, because you can't see if you have actually removed the spots - the dust hides them. I pulled out my scraper. I haven't used it in a while and mine was dull. I am not too good at sharpening it, so I pulled out a scraper/razor blade. I used the razor as I would a scraper at slightly less than perpendicular angles. The razor seemed particularly good since the spots were so small. The razor appears to have worked very well. 2-6 light passes over each spot and they all appear completely gone. You could clearly see the spots disappear as you passed over it. Sometimes they just flecked off.
I will sand and start finishing tomorrow now. Thanks a bunch for the feedback.

From contributor M:
Glad to help. If you're interested, the fastest/easiest way of prepping scrapers I've found to date is with a jig from Rockler. This jig absolutely rocks. It's hard to mess up. Renewing a new hook takes seconds. I've been able to reform a hook three to five times before having to re-flatten the cheeks and edges, thus allowing me to draw a fresh hook. I'm probably at this jig... oh... twice per week at most. My cab scrapers see a lot of use every day.

From John Van Brussel, forum technical advisor:
You may want to try a glue which is higher solid content. This will be less prone to bleed through because it will be thicker. Another option would be to use a UF resin which dries hard, sands well, and accepts finishes.

From the original questioner:
Thanks for the info on the scraper jig. I will look into it.

John, you are probably right about the glue. I have been using the Titebond because that was all a local wood shop had. I have used it with good results on the veneering jobs I have done in the past. I don't work with much veneer. But I really like the end results. It is hard to get wood as nice looking as certain veneers that are available. I will have to look into other glues for future attempts and maybe sizing as well for certain porous veneers.

From contributor I:
Instead of trying to remove the bleed through, why don't you try glue sizing the entire face and seal up all the pores? Then you can sand the face and get a more uniform surface for stain.

From contributor B:
By "bleed through," do you mean areas of highly figured grain where the glue works its way upwards from the substrate? I had that happen with some sapele pommele veneer where nickel-sized areas came out shiny-dark. A test sample had spots that would not absorb stain (dye). I was afraid that the dye stain would absorb unevenly because of glue in the pores of the veneer in some places. Sanding or scraping wouldn't have helped because it seems that the glue was soaking upwards from underneath. It seemed a bit like the opposite of splotchy stain in certain woods (like curly cherry or pine).

My solution was to use a washcoat before staining, stain, seal, and then a toner coat to even out the overall color before the clear topcoats. I don't suppose you could get a very dark finish this way, but it worked well for the medium-dark finish on a sapele and pommele table.

From contributor D:
I sand with a Bosch 4 inch belt sander using 120 grit belt, to just clean off the glue and tape. I have a lot of experience with the belt sander and I can control it. Then a random orbit sander - 180 grit, 240, 320, 360. This is on veneer 6 mm thick.

The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor J:
I've come up with a technique to eliminate bleed through while vacuum veneer pressing. I use a generous amount of PVA glue, lay down the veneer, and then lightly spray the top of the veneer with a mist of water. I press down the veneer, simply to ensure full glue contact. I then lay the non-stick (plastic coat) side of freezer paper on top of the veneer, and then place the caulk on. I place this in the press for anywhere from 60-70 minutes, and then pull it out. At this point, the glue between the substrate and veneer has set, but the freezer paper has kept the glue that bled through from setting.

I mist the veneer and wipe with an absorbent rag. The semi-set glue on the surface comes completely off after a couple rounds of misting and wiping and then I let it dry. Occasionally I have a few bubbles appear if I pulled the board from the press too soon, but the technique works great. I was able to press over 900 SF of veneer this way, without a drop of bleed-through appearing on the finished work.

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