Hey Guys,
Putting acid right on to the piece is very wrong! You can even damage the piece by doing so.
What you need is a small sharpening stone, with an extremely fine grit. You can get them about 1" wide x 3" or 4" long and maybe a 1/4" thick. Take the item to are testing and run an area that is not too visible, along he stone for about 2". It should leave a fine line of gold on the stone and virtually no sign of anything on the piece. Then place a tiny drop of 14K Acid on the line near one end. If the 14K acid makes the gold disappear where it touches then it's probably 10K. If the 14K acid does nothing to the gold line, try a tiny drop of 18K Acid, if you have it and so on. If the 14K Acid doesn't cut the gold line the piece is at least 14K or higher.
Never put acid on the piece!!!