Help With Zinc And Solder
We often frame our pieces with zinc. Recently, the solder holding the hanging ring to the zinc has suddenly released with obvious disasterous results. We have used this method for several years and had no problems until recently. The solder at the joints is holding fine, only the spots where we added a ring to hang the pieces is releasing.
What you have explained sounds like a cold solder joint. There are several reasons this can happen, and several ways to stop it from happening.
1. Make sure the rings you use are made out of copper or brass. If they are made from a metal that is not compatible with zinc or lead (like steel or aluminum) you will get a cold solder joint. That means it looks like it's soldered together, but, in fact, it isn't. The solder isn't forming a bond with the metal of the rings.
This sounds like the obvious reason for your problem since it has just started happening. Check with your distributor to find out what metal the rings are made from.
You can make you own rings from 14 or 16 gauge copper or brass wire which is cheaper than buying ready made rings, and you'll be sure they are made from the correct metal.
2. If the rings are a compatible metal, solder will "take" faster to the copper or brass rings than it will "take" to the zinc. To solve this problem, tin the zinc in the area where the rings will be attached before you solder the rings in place. Then, as you solder the rings in place, make sure the solder flows onto the zinc. Once you see that happen, remove the soldering iron, but continue to hold the ring in place until you see the solder set up.
3. Another way to attach the rings is not to miter the corners of the zinc on the top of the panel. Make sure the top piece of zinc goes between the 2 side pieces. This will leave holes on the ends of the 2 side pieces.
Make rings with long tails. Put the tails in the holes and solder them in place, making sure the holes are filled with solder and the bottom edges of the rings are embedded in the solder. This will give you double insurance that the rings won't pull off, since the tails as well as the bottom edges of the rings are firmly soldered in place.
I hope this helps,