Trying to learn more how to refine with borax. Hard to find a good video.
That is because borax does not work to refine actual metals (like the bars you bought)
Borax is a flux used to slag off organic impurities (such as ash from incinerated plastics paper etc. etc.) or inorganics (such as silica/quartz from crushed ore etc. etc.) or "certain" metal oxides (not actual metal) in a smelting process
You can read about smelting here ---------
https://goldrefiningforum.com/threads/smelting.25592/
So borax will do
NOTHING to separate the gold from the other metals in your metal bars
If your bars are primarily copper (like 90% or more copper) then the best method to part the gold from the copper is to run it in a copper parting cell
you can read about that here -------
https://goldrefiningforum.com/threads/electrolytic-copper-refining-cell.25596/
If the copper content in your bars is less then 90% you will have to remelt the bar & add more copper to get the copper content up over 90% to work properly in the copper cell (preferably 97 - 98 % copper)
The other (next best) option is to use it in what is called the stock pot as suggested here -------
If it's mainly comprised of copper, use in your stock pot. IF, there is any PM's in it you'll eventually recover it.
But again it (the metal bars) need to be high in copper to start with --- the stock pot is a method to recover "small amounts" of precious metal from solutions from "other" refining process
Outside of the above there is
no real good method to part (separate) the gold from your bars for more reasons then I can possibly explain right now
Kurt