Any form of room that has running water in it, if there is a window, the better, unless the work is done 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 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.

How To Prepare The Glass

Soak the glass in strong lye or potash for a time, then wash carefully and put into acid, then wash again and albumenize with the white of one egg to six ounces of water without ammonia. The plates should be slightly warm when being coated.

Coating The Plates

Hold the plate in the left hand, as you would for coating with collodion, flow with emulsion as you would with collodion, letting the surplus flow off the right hand lower corner, but do not let more than the gross surplus run off; retain enough to make a rather thick film; now move the plate so as to facilitate an even distribution of the film, then set the plate on the leveled cooling table.

The Cooling Table

This table should be a large slab of marble or slate with a perfectly plain and level surface; before using it should be cooled by placing ice or a refrigerating solution on it. The coated plates are laid on this level table, where the cold soon chills the emulsion, causing it to set, when they may be set up in racks and placed in the drying room or box, where in the course of a few hours, if the conditions are favorable, they will dry and are then ready for use.

The Drying Room

The drying room, or box, as the case may be, must be kept cool, and if any current of air is induced it should be cool and constant, so that the drying may proceed with perfect regularity until the process is complete. Should the drying by any means be checked a line will be formed on the plate, showing where the drying stopped for the time.

Plates may be dried by a current of warm air, but they are much more likely to frill during development; and a very little heat will melt the coating.

If the plates are dried by an induced current of air, the process may be hastened by placing dishes, filled with chloride of calcium, in the air passage to the drying box or room. The chloride will absorb all the moisture from the air passing over it, and the dry air will take up the moisture from the plates.

When the chloride of calcium becomes too damp for further use, place the dishes containing it in an oven and drive off the moisture by heat, when the dry calcium may be again used. By employing such means the plates may be dried in a few hours.

After the plates have become dry, they should be packed in good light-tight boxes and kept in a dry room until wanted for use.