Mirror Flux

Hello, I learned stained glass 25 years ago. We used a product called Mirror Flux and had no problem with the silvering of the mirror going dark. I have been unable to find this flux. Can you help?
Linn

Answer

Hi Linn,

I don't know of Mirror Flux as such, but you can use any non-acid flux such as Canfield Solder Magic Gel Flux, Laco Paste Flux, Safety Flux, or La-Co Brite Flux. Tallow is also a very safe, natural, non toxic and acid free flux.

As you might already know, black rot, those black spots that you see around a mirror, is caused by the tarnish of the metals used to make the reflective surface. As soon as the mirror is cut, the edges become exposed to various corrosive agents. Ammonia in glass cleaner, the acid in flux and patina, even the adhesive backing on copper foil may corrode the mirror backing.

You must protect the mirror edges with a sealant. Mirror edge sealants and silver protectors are available through most stained glass suppliers. Even a good, high quality varnish or unbleached shellac will work. Be sure to coat all exposed edges of the glass before foiling or leading. For an extra measure, I coat the entire back of the mirror. This protects the back and helps to prevent scratches.