copper foiling

[Javahut]

Something you might try, if interested.
I realize you are in a salt water environment due to your physical location, but if your foil is already fairly clean, you might try a flux made up of rubbing alcohol and glycerin, 1:2 ( working from memory so if that ratio doesn't work, reverse it, start with a small amount in the mix. Neither is expensive)  It is non corrosive to glass paints and enamals, but you will have to solder a touch slower, but it does work.

and please keep in mind that the dust from copper sulphate can cause blindness, so watch just how "dry" your mix is in that paste.

[Enrique Laks]

Thank you Javahut, we are always interested in learning new methods and techniques, even more so because we are so far away from the tech centers. We appreciate your trying to help us. Although Costa Rica is surrounded by two oceans we live high on the mountains, no salt water environment. We will give a try to your suggested flux formula and will be careful with the copper sulphate, making sure no powder comes out of the process. Health hazards are most important in this trade.