Soldering a Dome to a Backplate
by Judy Larson
During the process of making a pair of silver and gold earrings inspired by organic Israeli designs, I needed to solder a hammered gold dome to a flat sheet of silver.

For safety, there must be a way for the air under the dome to escape. If both pieces fit flush together, the rapidly expanding heated air under the dome could cause the domed disc to pop off at a high velocity. It could strike you or those around you causing burns, hit something and break it, or land on a highly flammable surface and heaven forbid, start a fire.

Note: Whatever method used to solder two pieces together where there would be air that needs to escape, for your protection at the very least wear non-flammable clothing and face and eye protection. Better safe than sorry!

The easiest way to make sure the air can escape is to drill or punch a small hole in the back plate, or in an inconspicuous place on the domed disc.

For these earrings, since I challenged myself to make them a "design as you go" project with leftover materials from other projects, I decided against that. You may want to try one of these two options.
Instructions
Option 1: Heavily Textured Dome and Smooth Backplate: The uneven lower edge of the dome provides an avenue for the air to escape.
Heavily hammered discs will have uneven edges. After doming the discs, lightly sand the bottom edge of each disc, flattening only a few spots, not all the way around. The areas left not sanded will be where air can escape. If you are still worried that there is not enough room for air to escape, use a round file in one spot on the bottom edge of the dome to remove a bit of metal.
Judy Larson's Soldering a Dome to a Backplate - Option 1: Heavily Textured Dome and Smooth Backplate: The uneven lower edge of the dome provides an avenue for the air to escape., Metalwork, Butane Torch, Soldering, Solder, Soldering a dome to a back plate
Judy Larson's Soldering a Dome to a Backplate - Option 1: Heavily Textured Dome and Smooth Backplate: The uneven lower edge of the dome provides an avenue for the air to escape., Metalwork, Butane Torch, Soldering, Solder, Soldering a dome to a back plate
Place small amounts of paste solder around the inside bottom edge of each dome. The lower dome in the photo shows too much paste solder, which is what a lot of people would use. Use about half that and only inside the dome at the flat sanded areas. That way, solder will not fill any gaps, which could impede air escape.

Place the piece on the flattened back and heat until the solder flows.
Judy Larson's Soldering a Dome to a Backplate - , Metalwork, Butane Torch, Soldering, Solder, Soldering a dome to a back plate
The lower edge of the hammered dome is visibly uneven. It was hidden with the coiled silver rings soldered around the edge.
Judy Larson's Soldering a Dome to a Backplate - , Metalwork, Butane Torch, Soldering, Solder, Soldering a dome to a back plate
Judy Larson's Soldering a Dome to a Backplate - , Metalwork, Butane Torch, Soldering, Solder, Soldering a dome to a back plate
Option 2: Smooth Dome and Heavily Textured Backplate: The low areas on the surface of the backplate provide an avenue for air to escape.
Sand the bottom edge of the dome flat.
Judy Larson's Soldering a Dome to a Backplate - Option 2: Smooth Dome and Heavily Textured Backplate:  The low areas on the surface of the backplate provide an avenue for air to escape., Metalwork, Butane Torch, Soldering, Solder, Soldering a dome to a back plate
As in the photo in Step 2, here way too much solder was placed inside the lower edge of the dome. Use half that, and leave one area with no solder at all. Heat until the solder flows.
Judy Larson's Soldering a Dome to a Backplate - , Metalwork, Butane Torch, Soldering, Solder, Soldering a dome to a back plate
Judy Larson's Soldering a Dome to a Backplate - , Metalwork, Butane Torch, Soldering, Solder, Soldering a dome to a back plate
Because the bottom edge of the domed disc was sanded flat, it visibly looks like it is soldered fully around to the backing, even though it is not. There is no need to hide the edge of the dome.
Judy Larson's Soldering a Dome to a Backplate - , Metalwork, Butane Torch, Soldering, Solder, Soldering a dome to a back plate

Materials

22 Gauge Dead Soft Argentium Silver Sheet - 6 Inches
H19-22SM6
  • Lesson Quantity: 1.00 pieces
  • Purchase Quantity: 1.00 1 Inch
  • Price: $61.68
  • Gold Club Price: $46.26
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Tools

Basic Soldering Kit
G15-4
  • G15-4
  • Lesson Quantity: 1.00 pieces
  • Purchase Quantity: 1.00 each
  • Price: $58.95
  • Gold Club Price: $44.21
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Blazer Big Buddy Turbo Torch, White
TRCH-8012
  • TRCH-8012
  • Lesson Quantity: 1.00 pieces
  • Purchase Quantity: 1.00 each
  • Price: $40.00
  • Gold Club Price: $30.00
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  • Category: Metalwork
  • Technique(s): Butane Torch Techniques