Tannin marks after Oak glue up

[JoeS]

Never had this problem before, but working in some American oak this week on a small table and after wiping away the glue with a damp brush like I usually do I've ended up with what I think are tannin stains. Drat and double drat!!!

For now that means lots of fiddling sanding to do...I'm assume the marks will come off with a sand? But how to avoid this? Just be more careful with glue? I've always wiped my joints with a damp cloth/tooth brush for squeeze out.

Thoughts and techniques? I'm surprised in hindsight I've never experienced this before - is american oak particularly heavy in Tannin?

 

[ian8555]

Your approach is fine, damp cloth and toothbrush are a sensible approach. Somehow there seems to have been a very fine deposit of something metallic that has caused this to happen. Any metal drilling / grinding nearby recently, could be just a few specs of dust

 

[Peter Sefton]

Might sand out, if not use oxalic acid. Might be caused by recent iron work in the workshop, can come from some abrasives, dirty cloths or water. Make sure everything is clean.

Cheers Peter

 

[JoeS]

Interesting - I actually was grinding down some old chisels today and cooling them in the water bucket which I then used to clean the joints with. Really remarkable that this made that much difference.

Annoying but good bit of learning...and hopefully I can get it off without too much drama. Big thanks Peter and Ian.

 

[Cabinetman]

I was taught not to use water as it will creep into the joint though capillary action, so all I’ve ever done is scrape with something suitable and then a dry wipe. Have you been doing anything with wire wool? The bits from that are plentiful. Should sand off fairly easy.

 

[ian8555]

I was taught not to use water as it will creep into the joint though capillary action, so all I’ve ever done is scrape with something suitable and then a dry wipe. Have you been doing anything with wire wool? The bits from that are plentiful. Should sand off fairly easy.

Yes that is sensible advice and a well taught approach. From a commercial manufacture side it is very fast and produces a great result to use water, particularly warm water, if the wood is properly dry and you have a dry shop, any moisture added during the removal of glue will have gone by a day or so, just need to look out for potential issues like this contamination.