I usually soak the Sand dollars in a bucket of 9-1water/bleach overnight and
then lay them out to dry in the sun on an old towel. I will sometimes rinse
the test out for a few seconds in a cool water bath (I don't out a stream onto
it beacause the water pressure might break it) It takes about 2 hours to dry
completely ( the bleach evaporates off)  and then I then brush them several
times with a watered down mixture of Liquitex Acrylic Gloss Medium & Varnish.
I let each coat dry for an hour before I put another on. A small bottle runs
about 6 bucks but it is well worth it. You can get it at any art or craft
supply store that sells acrylic paint. (there is a website that lists the
retailers..  http://www.liquitex.com ) You an also use a matte medium  by the
same company. The glossy doesn't really add gloss to the sand dollar but
really adds strength. The SD soaks it up and it apparently makes fewer micro
holes in the test. Just be sure to rinse the brush very well afterward because
when it dries, it is watersafe and will not come out.  I have also used this
stuff on various other echinoderms and fossils.
Its a good thing
Sarah
 
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