My students are having trouble with the copper foil coming off as they finish their hinges. Any suggestions? I remind them to clean glass well, burnish well and try to avoid excessive contact with foil by the soldering iron.
Beki Mountain View High School Mesa, AZ
Answer
Hi Beki,
The advise that you're giving your students is very good, and they need to do as you are telling them. However, there are several reasons that could the foil could be pulling loose.
You need to have a few solder joints coming to the edge of the lid, where you solder on the tube portion of the hinge. There is quite a bit of stress put on that area every time the box lid is opened and, sooner or later, the foil will pull loose if the tube is soldered to a single long piece of foil. See Boxes 1 in the pictures below. I realize the hinge is different from the one you are making, but the type of hinge doesn't matter.
The other reason could be the way you are attaching the hinge. Here is a hinge technique that will prevent stress on the lid. Solder the tube to the back of the lid. Put tooth picks in each end of the tube while you are soldering it. The tooth picks prevent solder from getting in the ends of the tube. Once the tube is soldered on, tape the lid in position, to the top of the box.
Take two pieces of rod and bend them into an L shape. Remove the tooth picks from the ends of the tube and insert the short legs of the Ls in the ends of the tube. Solder the long legs down the side seams of the box back. You will see how that looks in the Box 2 pictures below.
By using that technique, the foil along the back of the box should not pull loose. However, having a few solder joints going to the back of the lid as well, will give you double protection for the foil.
