Either work outside, in a garage with the door open, or near a window. Wear a dust mask for an extra layer of protection.
Isopropyl alcohol is a basic solvent cleaner that works for in most cases. For pieces caked in grease or oil, use a stronger cleaner like acetone. Acetone is corrosive, irritating, and flammable. Wear gloves when you handle it and keep it away from open flames. If you get any on your skin, hold the area under running water for 5 minutes.
Don’t worry if the brushing scratches the metal a bit. A rough surface actually helps the solder bind better.
Look for a flux that is specifically designed for stainless steel use. This is usually printed on the product label. Use gloves and eye protection when handling acids. Other rosin-based fluxes are not effective for soldering stainless steel. Use a stronger, acid-based flux. If you’re soldering 2 pieces of stainless steel, wipe them both with the flux. If you’re soldering stainless steel to another metal, only wipe the steel.
Solder with some silver in it will also form a stronger seal. Remember that solder with silver takes longer to melt.
There are special soldering benches with clamps to hold 2 metal pieces in place. Consider investing in one of these if you solder often. Most table vises are also large enough to hold 2 pieces of metal at the same time. If you’re soldering something locked in place, like a pipe, then only secure 1 piece of metal.
The flux will bubble a bit when it’s heated. This is normal. To test when the metal is hot enough, touch a bit of solder to its surface without the heating unit attached. If it melts on contact, the metal is hot enough.
If you’re soldering 2 pieces of stainless steel, then skip this step. Solder is a thin metal wire that comes in a spool. When you melt it, unroll 6 inches (15 cm) from the spool to keep your hand a safe distance away from the heat.
If you’re using a soldering iron, hold the iron against the joint. Then touch the solder to the iron. Spread the melted solder along the joint as it flows down the iron. If you’re using a torch, don’t touch the solder directly to the flame. Heat the metal up with the flame until it’s hot enough to melt solder, then touch the solder to the metal.
If the piece you soldered is too large or fixed in place, bring over a bucket of warm water and scrub the joint with a sponge. Use a mild dish soap if the flux doesn’t come off with a simple scrubbing.
