Originally Posted by raspero
A man with a lot of bronze sculptures in his house wants me to help him. He has had them for years up in Mexico City where the air is dry. He moved to a seaside house down here and his bronze has begun to develop little white crusty spots in places.
I am not a patina expert. I do my own work but I don't want to do something stupid to his. There are no patina experts down here. There are also none of the chemicals that Ron Young recommends for bronze disease.
I am considering using a small knife blade and scraping the white powder off and then coating the pieces with nitrocellulose lacquer. They definitely need to be coated exposed to the ocean air as they now are.
Hard to say what it is exactly, one can't assume it's "bronze disease" but in fact it could be fungus, mold, or even a previous coating or lacquer that is failing. It needs to be carefully removed, and not by scraping with a knife! Would you scrape dried bird droppings and mud off the finish on a brand new car using a knife? same idea.
It could be just poor practices post patina of the bronzes, they were not rinsed and neutralized properly to remove acid residues, or they applied wax or something over them while they were still a little damp. I'd lean towards having not rinsed and neutralized the acids/chemicals, and they lay dormant in the dry climate and are being activated now by the moisture.
Seems to me in the old days the masters applied patinas with one of those blow torches that used liquid fuel, made a nice wide spread flame to heat rather than trying to "weld" with, and then rinsed the bronze well and neutralized the acids.
I've done patina hot, rinsed real well and then dipped the bronze in a tub filled with a baking powder/water solution, rinsed and heated it warm enough to dry it well, then applied Johnson's paste wax on it while it was still hot.
I am definitely not a fan of globbing on cheap lacquer over the bronze, like all paints and coatings it will change color and fail eventually and have to be removed again, how many times does someone really want to strip lacquer off and redo something like this?