How can I tell the difference between gold and gold-fill? Is there a home-made way to do it?

I make jewelry, and I have mixed up some solid 14k gold components with 14k gold-fill and I can't tell which is which on some of them! HELP. Shame on me for keeping such a messy workspace but there it is. I'm hoping beyond hope one of those baking soda and vinegar solutions is out there for me to do this at home rather than having to buy an expensive tester or go to a jeweler.... Thanks in advance for your help.