Soldering two pieces of silver together, or repairing a crack in a silver object, requires different materials and techniques than most other metal soldering jobs. Even if you already have a workspace ready, read or browse that section to learn about the changes you may need to make before starting work.
Some specialized businesses may require the use of silver solder to join other materials such as brass or copper. In these cases it may be good to look for more specific information on this process, such as soldering copper pipes
Steps
Part 1 of 2: Prepare the Work Area
Step 1. Find a block of welding carbon or other suitable work surface
The welding will not work well if too much heat is lost in the air or on the work surface, so it is necessary to find a suitable surface with low heat conduction. A block of coal may be the best option, as it reflects heat to create the high temperature required to solder the silver. A magnesium mouth or brick furnace are other viable options, and they can stand up to use for other projects than a coal block.
You can buy them at craft stores and jewelry stores, and they are similar in shape and size to a regular brick
Step 2. Purchase silver brazing
Silver brazing is an alloy formed of silver and other metals designed to bond with silver but which melt at a lower temperature. You can buy it in pre-cut pieces or in sheets or threads and cut 3 mm pieces with a cutter. Do not use lead based alloys, they will not work and will be difficult to remove.
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Attention:
avoids alloys containing cadmium, its fumes are dangerous if inhaled.
- If you need to cover a crack, you could use a less pure alloy that melts at a lower temperature. To join two pieces together use "medium" or "hard" alloys that contain more silver and allow for stronger welds. Remember that there is no industry-wide definition for these terms - if you are switching brands and want results similar to what you are used to, look at the percentage of silver content.
Step 3. Use a blowtorch, not a soldering iron
Do not use a soldering iron because it is usually used for low temperature lead solder and can ruin precious metals. Purchase a small oxyacetylene torch from the hardware store, preferably with a flat "chisel" head instead of a pointed one.
Silver quickly dissipates heat away from the place exposed to the flame. For this reason, a small tip torch can cause the weld to go much slower
Step 4. Select a general purpose flux or brazing flux
A "flux" serves to clean the silver surface and facilitate heat transfer. It also helps remove oxides that could interfere with the bond. You can use general flux or "brazing flux" specifically for silver and jewelry.
- "Brazing flux" is used for high temperature joints where the surface of the metal objects themselves is chemically altered. Although jewelers also refer to this process as "soldering", "brazing" is technically the correct term.
- It doesn't matter what kind of flow you buy (eg paste or liquid).
Step 5. Use a fan if necessary
Open windows or turn on a fan to minimize the amount of smoke inhaled, move the air over the work area and away from you. Keep the air away from the object itself or the cooling effect will make the welding process difficult.
Step 6. Find some copper tweezers and tongs
Copper tongs are recommended as they are capable of handling the high heat and will not corrode and spoil the pickling solution described below. Tweezers are useful for holding silver items in place although these can be made of any metal.
Step 7. Take precautions such as glasses and an apron
Safety glasses are essential to protect your eyes from accidental splashes, since you may need to look closely at the joint. A denim or canvas apron minimizes the chance of burning clothes.
Avoid baggy or hanging clothes. Pull up your long sleeves and tie your hair up, if you have it long, before starting work
Step 8. Prepare a container with water
You will need a container full of water to rinse the silver at the end of the process. Make sure it is deep enough to fully immerse the object.
Step 9. Heat a container full of "pickling solution"
Purchase the "pickling solution" or acid solution used in soldering, particularly for its suitability for silver. It is usually available in powder form. Just before starting to weld, dissolve the powder in water and use a pinata or pot to heat it according to the manufacturer's instructions.
- Do not use a piñata, microwave, or oven that you intend to use again for cooking. The pickling solution can leave behind a metallic odor or even traces of toxic materials. Never put steel in contact with the solution.
- Most of the solutions can last for weeks.
Part 2 of 2: Join the Silver
Step 1. Clean the silver
A degreasing solution is recommended for greasy or heavily used silver. If there is surface oxidation it may be necessary to put silver in the pickling solution before soldering. Alternatively, you can use 1000 grit sandpaper to make the surface rougher.
Step 2. Apply flux to the joint
Prepare the flux according to the instructions on the package if it is not ready to use. Use a small brush to apply it to the silver object (or objects). Some put it only where the solder will be, to limit the amount of alloy that will end up in the wrong place. Others prefer to apply it on a larger area, to minimize the risk of fire damage, but this is not recommended for beginners.
Better to use a small amount of flux in a separate container, because repeatedly dipping a brush into the original bottle can add dirt and affect the ability to function
Step 3. Put the parts to be joined in place
Spread the two parts side by side on the welding block. Put them exactly how you want them to be joined; be careful: they must touch each other to be joined correctly.
Step 4. Put the alloy on the joint
Use a pair of tweezers to pick up a piece of alloy and gently place it on one end of the slot or space to be joined. Once melted, the alloy will be carried by the heat wherever the flux has been applied so that it is not necessary to cover the entire length of the space to be joined.
Step 5. Heat the objects until the alloy melts
Turn on the flashlight and set the heat to maximum. Start by holding it about 10 cm from the joint, constantly moving it in circles to make sure you warm all the parts. Slowly, move it closer to the joint focusing on the metal parts closest to the alloy, not the alloy itself. Reached its melting point, the alloy will melt quickly and will be brought to the areas of the silver covered by the flux.
- If one of the objects to be joined is thicker than the other, heat the thicker object from the back until the alloy melts and then briefly heat the thinner object.
- Use tweezers, if necessary, to hold objects in place, but keep them at the ends away from the fire. You may need to press on thin points of the silver to dissipate the heat and prevent the thin part from melting.
Step 6. Immerse the object in water and then in the pickling solution
Let it cool for a minute, then cool it again by putting it in water. The solution described above is an acid bath which serves to clean the jewelry after brazing. Dip the silver in this bath using copper tongs and leave it for a few minutes to remove flux and oxidation. Avoid any contact with skin, clothing and steel tools as the solution can be corrosive.
Step 7. Rinse the silver
Rinse the joined silver parts. Wipe dry with a clean cloth. If the process is completed successfully, the silver will remain permanently bonded.
Advice
- If excessive welding has led to a lumpy appearance, use a file to remove the excess.
- If the weld doesn't flow properly, stop, let the object cool, and start over. Clean thoroughly with a cloth and pickling solution.
