Help identifying the cause of the damage to the finish on this table would be greatly appreciated, as well as, some recommended techniques for removing and refinishing. My first thought was stripping and using oxalic acid solution but I wanted to determine what exactly is the cause of the black almost mold looking marks on the wood. Any help is greatly appreciated. Thanks in advance

Jay, I'll just welcome you to the forum. I'll leave the suggestions to others.....refinishing and repair isn't something with which I have much experience. I am curious, is this table something you built? If yes, what is the finish that's on it?

Your solution would be my only suggestion. Our resident furniture repair expert, @kmealy, will probably chime in with some additional help. 

+1 for what @Gene Howe about @kmealy. I am terrible at finishing/refinishing. It looks like a combination of heat and moisture damage but that's just a guess.

 

Welcome to the Patriot site!

Edited November 18, 20214 yr by lew

It looks like the typical stain of oak (tannin), iron, and water.    The usual cure for this is strip, oxalic acid, and refinish.  I cannot tell from the pix if it's veneer or not, but it could be solid panels because of floating joinery.   If veneer, be careful in sanding as to not blow thru it.   It's probably best for color matching to do the whole top rather than try to recreate the center as a perfect match to the ends.

 

If it's not the above type of stain, the other two bleaches may work.  

I also am not a finishing expert, but here is my guess.  Is it possible that someone tried to rub out between coats of a water based finish with steel wool?  If so, maybe that is rust damage from the steel wool. Just my WAG.

Tom, your WAG may not be so W. Sounds reasonable.

Welcome aboard JayOne, glad to have you here.

Oxacilic acid is used to bleach out the iron stained wood.  The stipper is to get down to bare wood to let the oxacilic acid work.

If after the finish is removed and the black color is also removed it may have been captured in the finish such as was writen above steel wool dust.

When finishing get the book from Jeff Jewit it explains it very well and simply.  

Once stripped and if necessary bleached.  

*Sand to 220 with care from 150 and if veneer be extremely careful.

Then reapply you dye to set the background color.  

Then reapply your stain to the the foreground color.

Vacume after sanding and before application of the top coat.

 

2 hours ago, Michael Thuman said:

Oxacilic acid

 

*oxalic

 

 

This is almost as interesting as watching a video of the Keystone Cops when I was a kid..

 

Interesting how someone mentions steel wool and the whole herd falls in line and agrees..

 

This must have been one hell of a bad refinisher to have used all the steel wool in one small area

 

compared to the rest of the table top... I remember when I apply a new finish on a table top. I also use 0000 steel wool between each coat but hey the top must be dust free before the next coat can be applied.  As decent as the rest of the top looks you would think this was what happened so do you all believe that guy that mentioned steel wool. Also if a person can't see a pile of steel wool then he don't need to be messing with refinishing anything!

 

 

 

And it looks like he did a good job of removing the steel wool on the rest of the table top so maybe he forgot and piled all the waste in that one area... 

 

 

 

Looks like a scorch mark to me, maybe with a hot pan or an iron.  Could also be mildew. Hard to say much without knowing what kind of finish.  That said, I don't think there is any fixing it up.  Best to refinish the whole top. 

 

.40

3 hours ago, kmealy said:

*oxalic

 

Thanks for the correction Keith much appreciatated.

 

3 minutes ago, Michael Thuman said:

Thanks for the correction Keith much appreciatated. [sic?]

 

I just used some oxalic acid yesterday.  It's vaporized in a bee hive to kill parasitic mites.  So a different application.   But the stuff I use is specifically formulated for that purpose.

 

At one of the bee clubs I go to, one guy keeps calling it oxicilic acid and I keep thinking new beekeepers are never going to be able to find it spelled that way.  The first time I heard him say it I wondered just what he was talking about.