Does anybody know why sandblasting turns 18k yellow gold from yellow good looking color to a kind of a grey/yellow and you need to heat and throw in pickle a few times in order to restore good yellow looking? I mean what happens while you sandblast? of course matte surface has different appearance than smooth one but this shouldn’t affect color.. I know how to restore yellow color thanks to depletion gilding but I wonder why sandblasting seems to change gold color? does it remove from surface more easily gold than silver or copper inside the alloy and that’s why gold “becomes” grey? if not what happens?
I think Rob is on the correct path, although it’s not because the 18k is soft. If your sand isn’t perfectly clean, it maybe imparting impurities into the very fine surface texture created on the metal. Body oils can cause discoloration, also. I found that a good cleaning in an ultrasonic cleaner, or an Ionic-cleaner along with steam cleaning did the trick. I never had the need to heat and throw in pickle.
I like the contrast between the brightly polish areas and the sandblasted areas and would sometime use in some of my designs, as can be seen in this ring for my wife.
Because the sandblasting, and the medium I use, is such a fine texture, it tends to ware quicker, so I would usually use a heavier texture with my designs.
We often bead blast 18 kt recessed areas. We then electro plate the pieces with 24 kt solution. After that we polish the non recessed areas. The 24 kt recessed areas give off a really nice glow.
I use glass beads to sandblast gold and silver. Some of the other available media is dark in color and has sharp edges, they do tent to embed themselves and dirty up the area. Glass beads, which are more rounded in shape, don’t seem to embed and don’t change the color; at least for me. For a recessed area, I like the idea mentioned to plate with 24K. Will have to try that out.
