Topcoating Over Gold Leaf

Thoughts on whether and how to finish over gold leaf. November 25, 2008

I am trying to find a good clear coat for gold leaf. Because of the size (glue) used, nitro lac is out of the question. I am assuming this is because of the harsh solvents in it, like MEK and acetone. I have tried short oil varnishes with less than desirable results. I would like to try a 2K urethane. Does anyone know if this would work? What does the 2k stand for?

Forum Responses
(Finishing Forum)
From contributor L:
I didn't think you needed to finish gold leaf. Is it just an accent on the wood which needs finishing? 2K just means it is a 2 part polyurethane and it cross-links through chemical means instead of by oxygen.

From contributor J:
I agree with contributor L - gold leaf does not get topcoated. Any finish you put on it will degrade long before the gold. Finish your piece completely and do the gold leafing last, then just leave it alone.

From contributor T:
Are you saying real gold leaf or imitation? Sounds like you used oil size, which would not be receptive to hot solvents like lacquer thinner, but that would indicate you have matte gilding if real gold. If it's foil then it will tarnish without a clear coat. Shellac is normally used to top coat foil, or as a barrier coat before any other clear. Real gold leaf needs no top coat, as posted above.

From contributor S:
I'm guessing that you are doing oil gilding and not water gilding. Gold leaf that is 23 1/2 karat will not tarnish, 22 and less will eventually over time. A coating over a lower karat will protect it from oxidizing and overzealous housekeeping, which can eventually rub off the gold if a cloth is used for dust removal. It also can be used to tone the color of the gold. What is the application? Do you want to brush or spray a coating?

From the original questioner:
The gold leaf covers the entire surface of a coffee table, so I want to protect it from abrasion mainly. I used Rolco quick dry gilding size, which contains mineral spirits. I want a nice deep gloss finish; brush or spray, whatever would work best.

From contributor R:
Automotive painters clear coat gold leaf all the time. I would use an isolante before the 2k urethane just to be safe as far as adhesion. Most manufacturers of 2k urethane will have an isolante product.

From contributor M:
I would stay with a barrier coat of shellac. Once dried you can recoat with almost anything. Also unless you are into bright gold look, the color in the shellac will soften and age the leaf.

The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor A:
Just a quick note of caution – make sure not to use any of the Rolco Gold Sizes if you are using Old World Art Sealer after gold leafing. The Rolco adhesive and the Old World react together, darkening and leaving a very dark, matt finish which completely conceals the fact that you’ve used actual 24K gold (devoid of any metallic look as well).

After a few attempts with the two types of Rolco, and having put down 15 books of gold leaf, I ended up having to sand the leafing right back down to the gesso base and start over again; this time using the tried and true German Gold Size that doesn’t react with the Old World sealer.

Some applications require a sealer because the gold will scratch and be subjected to amateur cleaning attempts, etc.