The gathered tests and sand or mud must first be washed in a 100 micron sieve with flowing water to remove salt. They must then be dried and cooled.
A whisky glass is 3/4 filled with cool tap water and the powdery material from the sieve is sprinkled onto the surface. The best foram tests will float and drift towards the edge of the glass. The silica and other debris will either sink or float in the middle of the glass. If the water level is reduced with a bulb pipette then the tests will be stranded around the edge of the glass where they can be picked up with a brush which can be washed out in a petri dish of pure water. A 1/2" wick of kitchen towel can be used to dry out the dish by micro-siphoning. The dried tests can be sieved for mounting.