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Sweat Soldering Copper and Silver
Sweat soldering is the fairly simple process of joining together two or more pieces of sheet copper or sheet silver. It is used where you are joining larger/flat areas of metal together.
Sweat soldering is a simple process, athough it's still important to practice a few times so you can get the results you want every time.
Sweat soldering is used extensively in making jewellery as a way of layering copper of silver to achieve 3D effects in your jewellery.
The method of sweat soldering is absolutely identical whether you're soldering silver to silver, silver to copper, copper to silver, silver to bronze.... it doesn't matter which metails you are fusing together, but you should practice with the cheapest metal first, rather than ploughing straight in with some expensive silver sheet and making a boo-boo on the first attempt. For this reason, I'll be referring to copper mostly below when I outline and explain the steps to sweat soldering.
Sweat Soldering Copper
Sweat Soldering Steps:
When you are sweat soldering copper and other metals, before you start:
Make sure your two pieces are absolutely flat, that they sit completely flat against each other.
Sweat soldering is intended to solder together two large/flat surfaces, it's not how you'd solder small areas that touch (such as in a ring or bangle). If they're not flat, hit them with a mallet until they are. If your copper or silver isn't completely flat then the sweat soldering will fail.
- As always, it's imperative that the copper or silver is absolutely clean.
- Paint your flux onto the back of the smallest piece you are sweat soldering, using a small paintbrush - as you're painting the flux onto the copper or silver, if it's not coating smoothly and consistently then your metal isn't clean enough. The flux should form a film and not bunch up into small pools.
- Place pallions of silver solder onto the flux - when sweat soldering you need enough pallions to solder the two pieces together, as a rule of thumb you're looking to cover about 20% of your small piece. Make sure you place pallions near to the edges as this will help you by achieving a better sweat solder result, plus you'll be able to see when the two pieces are soldered together as you'll see the thin silver line of the solder appear at the join when it flows and melts.
- Heat up the small piece of copper or silver as quickly and consistently as you can. You need to make sure all the metal is the same temperature so think about which flame you're using on your torch and concentrate on getting the whole of the piece heated equally. You'll see the pallions of solder start to shine bright when they melt.
- The tricky bit: Once you see the solder melt on the small piece, flip it over and place it (using tweezers as it'll be red hot) onto the larger piece of copper or silver. Now you need to heat up the two pieces equally until the solder melts again and solders the two pieces together. Ideally, you need to use a firing block with ridges/honeycomb so the heat can get quickly to the middle/rear of the larger piece, or find a way to heat your sweat soldering pieces from the bottom .
- Wait until you can see the line of silver along the join line, indicating the pallions have melted and your sweat soldered copper is ready.
- Quench in water.
- Pickle to clean up your copper and remove the firescale.
Tools You Need to Sweat Soldering Copper or Silver
Assuming you have your two pieces ready to be joined, the tools you need to sweat solder in the method given above are (in order of use):
- Borax cone/borax (or liquid Borax).
- Silver solder. Tin snips to cut the silver solder.
- Firing bench, (which can be a few firing bricks on a ceramic floor tile).
- Gas torch.
- Big tub of plain water
- Pickle. (You can make your own from white vinegar and salt).
Other items you'll need or find useful might be a paintbrush or tweezers to transfer the pallions of silver solder onto your piece.
A lot of the itmes for sweat soldering you might already have, or can get hold of easily. The gas torch you need is a simple butane gas torch (just like you'd use in the kitchen to flame the top of a creme brulee). You can make your own pickle, rather than buying industry acid pickle (this is great if you're nervous about handling and storing acid in your home). Even the firing bench can be made quickly and cheaply by getting some ceramic floor tiles as a base and stacking up a couple of firing bricks on that.
Easy to Make Jewellery
Sweat soldering copper or silver can come into the category of easy to make jewellery because you can buy pre-cut pieces to work with, saving you the time and trouble to buy metal clamps, metal sheet and jewellers' tools such as a jeweller's saw and special blades.
Simply find two pre-cut copper shapes, or pre-cut silver shapes that you think would work well sweat soldered together. You can buy these online from an increasing number of suppliers. Simply search for copper blanks for enameling, a copper blank is just a copper shape and you can use it for sweat soldering, enamelling or even metal stamping!
Volume & Production
If you're sweat soldering some jewllery for yourself, why not take a "batch" approach to it and do several at a time. The longest part of the process is getting everything together, so it can take 15 minutes to produce one item, yet only 20 minutes to create a line of them! Sell your spares online, or start to build up a stock of jewellery to sell at local craft shows and jewellery fairs.