<p>Here's a video that demonstrates the process that Alan describes above: <a href="
Long ago, I used a Kodak solution in order to determine if fixer was still good but then, because I used the same procedures repeatedly, I just figured out when the testing showed my fixer had gone bad, and never surpassed that amount of film and paper to be fixed. Good idea is to err on the side of caution and toss fixer early.</p>