Sealing copper patina
Hi, the green and blue patinas are prone to being quite delicate; what sealant, spray or coating could I use to make it more permanent without damaging or ruining the colour, what I have tried so far seems to cause the patina to crack or loose its charm.
the patina is on embossed copper sheets.
The sealant that has worked the best for me so far is a lacquer by Peacock Laboratories called, Permalac. I use the EF formula which is more user and environmentally friendly....sort'a. The embossing on your metal should not make a difference.
Before applying, dip the item first in acetone and then let it dry to remove any oils that could prevent the lacquer from making a good bond with the metal. (if the color coating you're trying to protect is oil or wax based, applying a lacquer is not a good idea) I have not had the lacquer or the acetone harm the patinas, including both the blue and the green one. My website Classes page shows some photos of jewelry coated with the Permalac. The Industrial Metals Cuff has been coated with the Satin finish which is actually shiny. The Concentric Circles necklace has a Matte finish coating and the Aegean Cuff with the blue patina also has been lacquered using Permalac. I do not use lacquer on silver as the patina silver develops when worn is very beautiful.
I will be honest with you and say that the Permalac is not the most user-friendly of products! It can be difficult to work with. It is not water-soluble and even the EF formula has a very strong odor, so using it in a well ventilated room is a must. Because of the weather here, I cannot use the product outside. If you make a mistake, you must soak it off with a paint thinner like methyl-ethyl-ketone (M.E.K.) and start all over again with the patina. Yes, it's a pain! When applying, if any moisture gets between the lacquer and the metal, the lac dries milky. It does come in a spray, but living in damp, humid Florida here in the States, I've found that I have less troubles with the liquid form. I apply it by dipping the item or brushing on the lacquer with a soft, natural brush or a cotton swab.
I set the lacquer using a blow-dryer then let the item air dry until the lac is completely dry about 2-4 hours later. All the items I mentioned above have 2 coats of the lacquer. I like Permalac because when it's properly applied, you can't see it or feel it. (well, OK....naked metal does feel a bit different, but most folks would never notice it) It is also the only product I've used that prevents the metal from continuing to oxidize under the lacquer, and, it's durable.
Of course, while I have had great success with the product, I don't know what kind of patina(s) you are working with. I would suggest that you experiment with a test piece first.