Any form of room that has running water in it, if there is a window,
the better, unless the work is done [p045] at night. If in the
daytime, shade the window with heavy red orange paper; if gas is
used, shade the flame with a ruby globe or chimney, and cut a piece
of tin to fit in the pipe below the burner to cut off rays of light
falling through bottom opening of globe or chimney.
If there is no gas purchase a dry plate lantern.
Emulsion in the jelly and when wet on the plates is only half as
sensitive as when dry, so that it is not necessary to distress one's
self working in the dark.
When the silver and bromide are brought together and mixed, it
should be done in this dark room. The solutions are poured into a
glazed earthenware bottle, which can be tightly corked. When it is
required that the emulsion should be heated, put the bottle into a
tin pail, fill the pail with hot water and put on the cover and heat
in any convenient manner; when it is necessary to examine the
emulsion, remove the pail and contents to the dark room.
A thermometer for testing heat in liquids should be used to regulate
the temperature.
A deep porcelain tray is the best dish for holding the emulsion,
while it sets previous to washing. To prevent the emulsion from
adhering to the tray it may be waxed carefully, but leave no
surplus; when the emulsion has set as firmly as it will, it may be
cut up into very small squares for washing, but probably the best
way is to squeeze it through the meshes of very coarse canvas, such
as ladies use for embroidering on with wool. The shreds may be
permitted to fall into a fine horsehair sieve placed in a pan of
very cold water and allowed to soak for a time, when the sieve may
be raised, and the water will in a short time drain away [p046]
from the shreds. This may be repeated until the water, when tested
with silver solution, gives no precipitate of bromide.
After the emulsion is washed it must be melted and filtered before
it can be used to coat plates. These manipulations must be performed
in the dark room. For melting the emulsion use a small oil stove
placed in a tin box, the open side placed to the wall; set the dish
containing the emulsion on the tin box over the heat; or, a more
perfect arrangement is to take a tin or sheet iron bake-pan, make a
hole through the bottom near one end, and into the hole fix and
solder a tin funnel, into which you can put a glass funnel that will
hold a pint or more; set this pan on the tin box containing the oil
or gas stove, the end of the pan containing the funnel projecting
over the tin box towards you; fill the pan with hot water, which the
heat of the stove beneath will keep hot; into it set the dish
containing the emulsion to be heated or melted; when that has taken
place pour into the funnel to filter, through loose absorbent cotton
or a thin piece of chamois skin or flannel, as you prefer; the
funnel will be kept warm by the hot water in the pan surrounding it.
Filter into a pitcher with a lip suitable for pouring from, or a
small earthenware teapot would be better. You would be using the
emulsion from the bottom, and thus avoid air bubbles; when all is
filtered set the pitcher or pot into the hot water to keep of an
even temperature.