Tanin Staining in Maranti, Canbara or other Mahogany Species
Greetings:
I repair a lot of porches with 1×4 mahogany. I shoot stainless nails and sometimes get black streaks in the location of the nail. Does anyone have any suggestions for their removal or ways to avoid their appearance.
By the way, what’s the difference between Canbara or Maranti?
Handy Dan
Replies
I don't know enough about stainless steel gun nails to give any advice as to why. My guess is that they are not a high grade and thus still affect the tanin in the wood. But all the nails ought to react the same in that case. Perhaps some nails "pick up" a bit of steel from the gun as they're being fired?
Oxalic acid is the time proven remedy for black stained wood such as you have. This comes as a crystal powder in a can. You can get it at any good paint store. If they don't have it then it's not a good store. Mix up a bit and apply, the stain will disappear. The acid should come with instructions. The stuff is acid but rather benign as far as acids go.
It should be noted that "stainless steel" is a misnomer. It's an alloy (actually a wide group of alloys) that doesn't exhibit rust in normal circumstances (because in SS the "rust" forms a tight coating that cuts off further contact with the air). But SS is still prone to many of the chemical reactions that regular steel is.
With nails there is a certain compromise, as the types of SS that are most corrosion resistant are most apt to be brittle. (Plus, of course, the more corrosion-resistant varieties are more expensive.)