Hi AuMin----------
You have stated in your post that gold filled is better than gold plated... You are most certainly right. I buy karat gold and resell. I always buy gold filled items and refine them and resell the gold as pure. (Industry standards at 995 pure)
You are right on determining the amount of gold content in filled items. 12k/24=.50X weight X .05 or .10 = amount of gold. (1/10 or 1/20) Example of 12k 1/20 gold filled and if the item weighed 10 Grams, you would wind up theoretically with .25 grams of gold or 2.5% gold. On 12k 1/10 gold filled you wind up with 5.0% gold on the total item. I never buy filled or rolled gold for much money. Usually for about 60% of the estimated amount of gold content of 2.5 to 5.0% depending on the amount filled or rolled.
Example -- 1/20 14K at 10dwt. .05 X .583 X 10.0 = .29dwt of pure gold.
The gold filled or rolled items always produce more actual gold than gold plating does. I measure gold plating at the best at 1.5% downward to zero (gold Flashed). The best way to determine the amount of gold plating on an item, is to put 1 gram of the gold plated material in 10 ml of 50% nitric acid and if the plating comes off in small flakes then it is low gold plating, but if it comes off in whole plating, then it is high gold plating, usually around 1.0% to 1.5%. This takes some experience in telling the difference.
The big difference in gold filled or rolled is how you refine it. I refine quite a bit of the gold filled and I use regular Sodium Nitrate and Hydrochloric solution (sic) aqua regia. I try to make the pieces as small as I can. Then dissolve them. On what doesn’t dissolve due to the silver chloride coating the pieces, I take those and boil them in Ammonia Hydroxide and after all the silver is dissolved off the items, I then put them back in AR again and dissolve. Some times you get some items that this will not work on and you have to boil the items in nitric acid. I have found that most of the gold filled jewelry doesn’t have much silver in it, so dissolving it the traditional way is not much problems.
Closing advice, buy all the gold filled and rolled items you can, but just make sure you don’t pay much for them. It takes a lot of work to get the gold out of them. They pay off much better than gold plated items.
Catfish
