Boehm Stained Glass Blog: Replacing Cap onto Stained Glass Lamp

Tuesday, March 18, 2014

Replacing Cap onto Stained Glass Lamp

The weakest point of a stained glass lamp is the cap at the top. After years of bearing the weight of all the glass beneath it, it will often separate. In this case, the owner of the lamp noticed the cap detaching and brought it right in before it could fall and create further damage. Here is how I repaired it. (Click on any photo to enlarge, use back arrow to return to blog).

Below I'm holding the cap above where it disconnected. Notice on the right that the copper foil and solder has detached from the glass. Over time, the adhesive on copper foil may break down and thus weaken the bond.

Here, I'm pulling off the old copper foil and solder which was beneath the cap.

Once this was done, it was apparent that one of the four pieces of glass beneath the cap had become very loose. I removed it. The other three pieces were firmly in place.

In order for copper foil to adhere properly to glass, the edges of the glass must be ground down. In this case, the glass was not ground, therefore I used a metal file to grind the exposed edges.

After I removed the loose piece of glass, I cleaned off the excess old adhesive, foil and solder and applied fresh copper foil to the border as shown. The foil was then pressed into the glass using a "fid" or flexible plastic wand.

Whenever I replace a cap I always strengthen the bond by inserting flat braided reinforcement wire between it and the lamp itself. Here, I'm applying liquid flux to the reinforcement wire. Then I'll apply a thin layer of solder to it. This process is called "tinning". This acts as an adhesive which aids in the attachment of the reinforcement to the copper foil.

Here, if you look closely, notice the tinned reinforcement wire between the lamp and the glass.

Once the seam is soldered, the reinforcement wire disappears.

After fluxing and soldering the bond, I spray it with Kwik-Clean and dry it off.

Next, I've lined the outer edge of the opening with fresh copper foil.

Then I take the cap and pull off any old solder and foil by using needle nose pliers.

Then I wrapped 1/4" copper foil around the edge and flatten it onto the cap using a fid.

Somewhat visible on the lower side is a strip of the tinned reinforcement wire. This will bond with the edge for a strong attachment.

Here I'm applying solder to the outer edge after I've applied the liquid flux. Flux acts as a catalyst of sorts, making soldering possible.

Viewed from the inside of the lamp dome, I've added foil to the interior as well.

Here I've replaced the cap onto the lamp and added yet another layer of copper foil to wrap around the edge. This cap will be covered with another black metal lamp part, so it will not be visible.

After the foil has been fluxed, soldered, cleaned and dried, I apply black patina with an acid brush. In order not to contaminate the contents of the bottle of patina, I always work with just a capful at a time.

And here's the repaired cap. After its dried, I clean off the entire lamp and apply stained glass finishing compound to protect the solder and give the lamp a nice shine.