Quote Originally Posted by Dave Wooten
Put a sheet of photo paper face up in your darkroom and place some coins on the paper. After five or so minutes develope the paper.
This should be amended by exposing the paper first so it will develop to a light grey and then set it out with the coins on it. This will bump the paper over its threshold level and give a realistic test of the actual printing conditions. Any fogging will show a darker grey outline of the coins.