Recipe for convincing fake gold bars

Theo Gray tells PopSci.com How to make convincing fake-gold bars. He's never actually done it. He believes his recipe is more difficult to detect than the fake gold bars in Ethiopia's central bank.

(Anyone interested in gold bars should visit the Federal Reserve Bank of New York. Reservations are required to be let into the gold vault. If you don't have reservations it's still worth a visit for the ANS coin exhibits. Visitors receive some odd numismatic-related publications, like these free comic books.)