To use flux when soldering jewelry, you apply it to the joint before heating to clean the metal and help the solder flow smoothly.
Flux is an essential component in soldering, particularly for jewelry made from metals like silver, gold, and copper. It acts as a cleaning agent, removing oxides and preventing further oxidation that occurs when metal is heated. This clean surface allows the solder to melt and flow properly into the joint, creating a strong bond.
Here’s a simple breakdown of the process:
Why Use Flux?
Soldering involves heating metal to a high temperature. When metals are heated, they react with oxygen in the air and form oxides, which are essentially tarnish or scale. Solder cannot bond to oxidized surfaces. Flux performs two main functions:
- Cleans the Surface: It dissolves existing oxides on the metal surface where the solder will go.
- Prevents Oxidation: It forms a protective barrier over the heated metal, preventing new oxides from forming during the soldering process.
Without flux, the solder would likely "ball up" and refuse to flow into the joint, resulting in a weak or failed connection.
Step-by-Step Guide to Using Flux
Using flux is integrated into the overall soldering process. Here are the key steps focusing on when and how to apply flux:
- Prepare Your Joint: Ensure the pieces of metal fit together snugly where you want to solder. The surfaces should be clean (free from grease, dirt, or polishing compound).
- Apply the Flux: Using a small brush or applicator, apply a thin, even layer of flux to the joint area where the two pieces of metal meet and where the solder will be placed.
- As seen in guides like A Guide To Using Flux For Silversmithing, you apply liquid flux onto the metal.
- Position Your Solder: Place small pieces of solder pallions onto the fluxed joint or onto the metal near the joint, ensuring they are in contact with the flux and the metal.
- Apply Heat: Begin heating the metal with your torch. Heat the larger pieces first, allowing the heat to conduct towards the joint area. Heat the metal underneath the solder pallions.
- As you heat it with your torch, you'll see some little bubbles start to form. Continue heating steadily and evenly.
- The flux will first turn milky, then bubble, and eventually become clear as it reaches its active temperature range, indicating the metal is approaching soldering temperature.
- Solder Flows: Once the flux is clear and the metal is hot enough, the solder will melt and flow rapidly along the fluxed joint, drawn towards the heat.
- Cool and Clean: Remove the heat once the solder has flowed completely. Allow the piece to cool (often quenched in water after it changes color from red heat). Clean off the remaining flux residue (many fluxes are acidic and must be removed) using water, a brass brush, or a pickle solution.
Types of Flux
While the principle is the same, fluxes come in different forms and compositions suitable for various metals and soldering temperatures. Common types include:
- Liquid Flux: Often used for smaller pieces and finer work. Easy to apply with a brush.
- Paste Flux: Thicker than liquid, good for larger areas or when you need the flux to stay put on vertical surfaces.
- Powder Flux: Usually mixed with water to form a paste.
The choice of flux depends on the metal being soldered (silver, gold, copper, brass) and the specific solder used (which has a particular melting temperature range). Always use a flux designed for the solder and metal you are working with.
Safety Precautions
- Work in a well-ventilated area or use local exhaust ventilation, as flux fumes can be irritating or harmful.
- Avoid contact with skin and eyes. Wear appropriate safety glasses.
- Consult the Material Safety Data Sheet (MSDS) for your specific flux.
- Ensure all flux residue is thoroughly cleaned off the finished piece.
Understanding the role of flux and how to use it correctly is fundamental to achieving successful and clean soldered joints in jewelry making.
