“Hi Ralph! I was told that when working with gold filled you need a barrier flux before the normal flux is this correct? I just want to make sure I do everything right to make something gold filled because I was told there was an extra step!”
No, you do not have to use a barrier flux before a flow flux, but it can help prevent the copper coming to the surface, making your yellow gold look like rose gold!
When soldering any color of gold filled, you don’t want to overheat because this causes the brass inside to come to the surface and create the copper color that often happens when gold-filled is overheated.
To avoid this, many people use pure boric acid and denatured alcohol mixed and kept in a sealed jar for barrier flux. Dip the whole piece in that and let it dry before heating it. It forms a powdery looking coating over the gold-filled piece. Then, once the flux is powdery, use some “regular” flux as a flow flux and apply this directly to the area to be soldered.
I prefer to use Firescoff, as this is a barrier flux and a flow flux all together in one! Using Firescoff is like using a 2-in-1 shampoo and conditioner, it saves time, money, and product.
You use Firescoff as you would any regular flux, applied directly to the joint to be soldered, but also over the entire surface of the piece. It works best when the piece has already been gently warmed before the overall application of the Firescoff, causing the flux to adhere and create a protective white coating.
I use yellow silver solder with both yellow gold filled and rose gold filled items, as it flows easily and color matches well without breaking the bank.
You can file or sand your soldered gold filled pieces to create a smooth joint, but you do not want to be too aggressive as you don’t want to go through the gold layer to the brass core.