February 10, 2018 5:13 PM EST
Hi Mary
If your piece is fabricated not casted so it´s less porous you can skip the ultrasonic cleaner. This is better for casted pieces, if you don´t have one just rinse well and enough under running warm tap water.
With 18K gold you will have the fine gold surface after approx 5-8 times, 14 karat need more but depend how strong acid you use how long you will let the piece stay in the acid. When you heat the piece the surface cannot turned black. You need pickle until the surface will stay "gold yellow".
Trish is right, if you can change the design to use 14K gold as a base and just make silver base enamel with 24K gold foil it is better. I know sometimes this is not possible. Check the gold wedding rings in my albums. They were 3D printed, casted from 14K gold and then enamelled. I did the depletion gilding around 10 times sometimes the rings were 24hours in sulphuric acid. After the enamelling the not enamelled part turned in kiln brown,light black or how to call the oxidized color. So I put the rings back to acid for approx 10 minutes not to ruin the leaded enamels and when the oxides dissapeared I continued with enameling.
Hope this helps 
Rudolf
