Dafna,
To filter the layer of scum that forms on top of your mercury, you can also use regular typing/copy paper instead of laboratory filter paper. Simply cut a sheet of 8½” x 11″ paper in-half, giving you two 5½” x 8½” sheets. Fold the individual sheets into a funnel shape – leaving a very small hole at one end. Secure it with a single piece of tape and you have an inexpensive mercury filter. Use them once then throw them away.
Experiment with the size of the hole so that the heavy mercury doesn’t flow too fast or too slow. The sludge will stick to the sides of the paper and the mercury will usually be clean after it passes through two new filters.
It only takes a few minutes to complete the whole operation and it is wise to do it on a regular basis (weekly or even daily if you are making lots of dags).
Best of all, typing/copy paper is cheap and always available. I make up a batch of 20-30 filters so I always have them on hand, ready for use.
Thanks go to Ken Nelson for teaching this cheap and easy way to filter your mercury – back when he was first giving daguerreotype workshops at George Eastman House in the late 1990s.
Cheers,
Rob McElroy
Buffalo, NY