Joint Tape "Shadows" -- at Veneer Seams

Why does the area from which tape was removed accept stain differently? March 14, 2004

I do a fair amount of vacuum pressing and every now and then have trouble when staining or dyeing a veneered piece because the area where the tape was resists the color and leaves a lighter colored strip. I've noticed it on ash and most recently, curly Anigre. I use solid veneer tape and remove it with a scraper after wetting it. I use water-based aniline dyes and gel stains.

Is this just a matter of doing more sanding or is there something else going on? In some cases I don't think I could've sanded much more without going through.

Is it possible I am over-wetting the tape and saturating the veneer with the glue? I use a handheld taper and tape with the seam. I see some shops tape across the seam every six inches or so, but I'd hate to have this effect show up in that kind of pattern.

Forum Responses
(Veneer Forum)
From contributor D:
Just a guess - are you using a tape with animal (fish) based glue? This is a common problem with that glue. If you are, switch to a vegetable-based adhesive.

Use as little water as possible, both in application and removal. Excess water will cause the glue/adhesive to soak into the grain. In the case of animal based glue, this can actually cause a stain in some species. You can also get the same affect as you would from glue sizing.

From the original questioner:
Is there a way to tell what the adhesive is? I use tape from Veneer Systems. I'll try to give them a call next week. Thanks for the information - I'll cut back on the water.

From contributor D:
The company can tell you for certain what you have. It is difficult to detect the difference visually or based on performance. The animal-based may "stick" a little faster, but very little.

From contributor J:
Our (Veneer Systems) standard veneer tape glue is vegetable based. It is acid-free and non-staining. What you may be experiencing is an oxidation due to light exposure. Certain species are more susceptible to this than others. Cherry, for instance, is very susceptible to oxidation.

I recommend that you cover your veneers with black plastic or heavy canvas after applying the tape. I worked for a veneer manufacturer and we always covered our veneer samples with a heavy canvas for this reason.

Another culprit may be the water itself. We have some customers who use distilled water in their tape dispensers. Tap water contains a lot of minerals and it may be a case of hard water reacting with the veneer.

From contributor E:
Try wiping the joint line down very well with denatured alcohol. I've had the same problem you describe, and this helped. I believe you have glue residue in the veneer and the alcohol will help remove this.

From contributor A:
One thing you might also be doing with the water is over-"popping" that section of grain. I've done several things with white Anigre, both curly and flat, and it is quite quick to grain "pop." I usually use a 1/2 lb cut of ultra blond shellac on it before finishing.

From the original questioner:
By popping, are you saying that perhaps the area the tape covered has had the grain raised more than the rest of the panel? I do ultimately raise the grain on the whole panel and sand with 220 as well as scuff sand between wash coats of dye. Why would the shellac coat help?

I'm pretty sure the problem isn't oxidation - they aren't in sunlight very long and I've never had the problem with cherry. Thanks for the distilled water suggestion. I'll give that a try.

From contributor N:
I am having the same problem with a recent panel done in French walnut with a Carpathian elm burl inset. I I am a long time refinishing / restoration / conservation shop owner and find that transtint tinted lacquers work very well to hide a lot of this type of discoloration. Very good product and does not obscure grain at all. I use 3m blue, long mask, masking tape for my panels. Never did use regular veneer tape. You must sometimes be careful not to leave this tape on for too long, and must also be careful in its removal since it will pull fibers. I have recently indented the panels where the tape was and attribute this to too high a pressure, 25 HG, on the press.