QuestionHello and thanks in advance for your help. I'm a fledgling jeweler and work mostly in fine and sterling silver. A client requested a pair of earrings in 18K. I made a mold of the original earrings so I got an 18K pair cast. They look great but the color doesn't quite match the 18K posts & earbacks that I just purchased. The casting - after being tumbled in stainless steel shot (only for a little while), then polished with a 3M bristle disc (dark blue) is appearing a bit more green than the posts/earbacks. Thinking that perhaps the posts might be a hair tarnished, I soldered them on and pickled everything. The golds are still a hair off. To be completely honest I prefer the color of the castings and one would never see the difference while the earrings are being worn, but it just doesn't look professional to have them a bit off. Is there a way I should be finishing gold castings that would result in a different color? Should I be using any type of compound to finish. For what it's worth, I rely on my tumblers for initial casting clean up and for finishing.
Again, thank you for you help.
-Virginia
AnswerVirginia, I do not see fault with the finishing process. Stainless tumble shot will rarely leave a slight surface color but the 3m wheel should remove this as would any tripoli or even green rouge.
FINISHING FIRST
While tumbling works well for silver in most cases, with gold and silver, a finer polish can be obtained with the normal polishing compounds on a buffer/dust collector. The "desktop" models work fine. I use soft stitched buff of 6inch size, with a wonderful prefinish compound called "grey star" (or use tripoli) followed with a cleaning and final polish with Green Rouge or Fabulutsre. Avoid red rouge since it is so messy and the other compounds can remove slight scrtches left from the grey star or trpoli and produce a wonderful shine.
COLOR VARIATION
My coworker is much more concerned with color match than am I, though I do want parts to match well. He is almost obsessed with it and has brought some of this to my attention in the past. We have noticed with 18k yellow gold more slight variation in color than with 14k but all can have some variation. Why? The manufacturers make various colors of yellow gold. With 18k the mismatch is often because the maker of the posts, etc., used a slightly different color of yellow than the caster did!
I believe the color difference is in the alloys and not your finishing methods. Next time, you might specify a "rich yellow" if possible. This general term will get you a more yellow alloy. Some of the alloys are more pale yellow, some more pinkish and some more greenish.
Agreed, the color difference is slight and will not be seen on the ear for your 18k earrings. Still, I feel as you do about the presentation and want all to match.
In this case, with the actual gold mix being the most likely reason, there is little to do but to grin, come on, you can grin on this one, just for me...been there. And, bear it.
Let me know if you need more info. Feel free to use the "follow-up" option to get back on this question if you need to. Best wishes with it all.
God Bless and Peace. Thomas. June 19,2007 7:35PM
