Twice now, I have encountered a strange and worrisome finishing problem. On both occasions I used curly maple veneer on a man-made substrate. I used PVA glue (Titebond). On one occasion, I let the glue dry on the veneer and the substrate and then ironed it on. On the second occasion, I used clamps and cauls. The only finish I applied was blond shellac to give a light amber color. Within several weeks, parts of the curly maple developed a very unpleasant pinkish to reddish coloring. I don’t think it has anything to do with the shellac. I have sanded one of the surfaces and the pink coloring does not go away, suggesting that the entire veneer is affected.
What happened? Is it the glue? Any thoughts on correcting it? One of the projects was a labor of love and I hate to see it ruined. Thanks so much. I am one worried woodworker. Best, Paul Carroll
Replies
Paul:
I have also noted that same reddish color when I used store bought Titebond II and orange shellac. I figured the shellac reacted to the glue left on the surface.
I have not noticed the same reaction when using regular yellow glue, but I have ment to try it with my next Arts and Crafts piece.
I believe it is a reaction of the glue and the shellac .
Thanks
R13
Hi Paul,
You mentioned PVA Titebond in your post but it wasn't clear whether or not you used a straight up PVA or a precatalyzed PVA. I would bet it was a precat PVA.
Pinking can occur as a result of the ingredients found in precatalyzed PVA adhesives. A component used to initiate the cross link reacts with a particular genetic property of maple. This causing the pinking. You should not use pre cat PVA's with maple, either go with straight PVA or a UF resin.
This reaction is also more likely to occur in areas where there is high humidity, a bathroom cabinet (shower) or in a cabinet over the stove (boiling noodles)
John Ersing
Veneer Systems
John, Thank you. Yes I used Titebond II on both ocassions. You are the second or third to confirm the problem is the cross-linking agent in this type of glue. As to why it shows up on curly maple, another person suggested it was the light color and the seepage through the porous endgrain created by the curl. Thank you. Paul
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