Solder Border onto Zinc

Hello,

I was wondering if you could help me with a problem. I am making tealight lanterns where three sides are composed of glass with copper foil and the fourth is a zinc frame (all I have) holding glass foiled marbles. When I attempt to attach the zinc frame to the copper foiled edges of the other glass panels the solder gets this 'cruchy' look, like there are little bits in it. I am using a ton of flux, and made sure that the zinc was clean first. Do you have any idea why this is happening and what I could do to fix it?

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Answer

Your flux might be contaminated if you are using a liquid flux and dipping into the bottle each time. Once it's contaminated you will have all sorts of problems with your soldering. If you use liquid flux you should pour a small amount, from a new bottle, into another container, like a jar lid, and use out of that. Discard any left when you're done soldering.

Try using a paste flux rather than liquid and don't use "a ton" of it. When I solder zinc I use Nokorode paste flux (available at most hardware stores and stained glass supply stores), and there are other brands that most stained glass stores sell.

The crunchy look you described sounds like your iron isn't hot enough. Zinc takes more heat than copper foil, so either turn up your temp controller or turn it off all together.

Lastly, make sure you keep your iron tip clean when you're soldering. Wipe it frequently on a wet folded up paper towel or a wet sponge.