THE GLYCERIN METHOD 
97 
fixing fluids, will present so much difference in times that only general 
suggestions can be given. When the stain is satisfactory, wash in 
running water for an hour. If this second iron-alum is not washed 
out thoroughly, its continued action will cause the preparation to fade. 
Put the material into 10 per cent glycerin (1 part glycerin and 
9 parts water), and then allow the water to evaporate gradually in a 
place as free from dust as possible. Nothing is better than a Petri 
dish for this purpose, because it presents a large surface for the evapo¬ 
ration of the water in the mixture. If there is much dust, cut a piece 
of filter paper just the size of the dish and let it float on the 10 per 
cent glycerin. The liquid will soak through the paper and evaporate 
without exposing the material itself to the dust. The process may 
be hastened, safely, by warming up to 35° C. The temperature of a 
paraffin bath—45° to 52° C.—causes such rapid evaporation that the 
material is likely to shrink. 
When the glycerin has become about as thick as pure glycerin, 
the material is ready for mounting. Place a small drop of glycerin, 
with the material, in the center of the slide, taking care not to put on 
so much that there will be a confusing tangle. Use scissors constantly 
so as not to injure filaments by trying to tease them out. Put on a 
round cover. There should be just enough glycerin to come to the 
edge of the cover-glass, but not any more , for it is impossible to seal 
a mount if glycerin has oozed out beyond the cover. 
The mount should now be sealed. Canada balsam, various 
asphalts, cements, flat varnish, gold size, and other things have been 
used. Canada balsam is always at hand and seems to be as good as 
any. Preparations which had been sealed with gold size more than 
fifty years before have been exhibited in perfect condition, but they 
must have been hidden away in some museum, for a glycerin mount 
would never survive fifty years of laboratory use. The gold size, as 
painters use it, is likely to be too thin for sealing mounts. Put some 
of it in a 1-ounce bottle with a wide neck and leave the cork out until 
the gold size thickens a little. Should it become too thick, thin it 
with turpentine. 
Nothing but practice will enable one to spin a good ring, but 
a good cameFs-hair brush, a good turntable, and a balsam neither 
too thick nor too thin will facilitate matters. Give the turntable a 
spin, and with the brush touch first the slide about as far out from the 
cover as you wish the ring to extend, then gradually approach the 
