Flux prepares the surface of a metal to be soldered by cleaning away oxidation and grime. It's important to use flux every time you solder or the solder and metal will not fully bond and will be prone to break apart.

Flux come in a liquid, paste or a gel. Gel and pastes tends to be easier for beginners to work with since it stays in place when applied and doesn't drip into other areas. It also is less likely to creep under the surface of the copper foil or lead came itself, which can cause unsightly corrosion later on and weaken the structure of the stained glass project. Liquid is easier for applying over large areas.

Some brands of flux have less smoke and fumes than others, which makes working with them a bit more enjoyable. Buy small amounts of flux until you find a brand and type that you like. Pricing on flux runs from $5 to $8. Som gel fluxes can't be shipped by air because they are a flammable gel. Keep that in mind if you are planning on purchasing by catalog or online.

It's important when working with flux to keep flux remover and flux cleaner. Flux remover is important is flux gets under the foil or came surface to get it out of there. When you are finished with your project, you need to use flux remover and/or flux cleaner over the the entire project surface to remove any flux chemicals that may still be on the surface. You also need to apply flux cleaner before using a patina on the metal surfaces so that patina does not react with the flux chemicals.