Distilled water                       1,000 parts. 
Erythrosine “Y” brand                     1 part.

Prepare second bath as follows: 

Erythrosine stock solution               25 c.c. 
Distilled water                         175 c.c. 
Strong water ammonia                      4 c.c.

After removing the plate, dip it again face down to rinse off any particles of scum, etc., that may get in the bath accidentally.  This bath may be used for one dozen 8 by 10, when it should be thrown away and fresh bath used.

After the plates come out of the last bath, they should be stood on clean blotting paper to absorb the excess of solution.  I would also advise to use clean fingers.  Pyro. or hypo. on the fingers is a drawback to success.

After plates have been drained, place them in a cleaned rack in an absolutely light-tight closet, with air holes so constructed as to admit air but no light; the plates will dry in from eight to twelve hours.  They are best prepared in the evening, and, if the closet is good, will be dry in the morning.

After the plates are dry they may be packed face to face with nothing between them, in a double-cover paper box, and put in a dark closet free from sulphureted hydrogen gas, until ready for use.  I have kept plates for three months in this way, and they were in good condition.  Great care should be used in developing these plates, as they are sensitive to the red; get used to developing in a dark part of the dark room; occasionally you may look at the process of development in a little stronger light.

The exposure through the yellow screen with an erythrosine plate is about the same as if you had no orthochromatic plate—­a plain plate instead—­provided you are not using too dark a yellow on your screen.  This can only be determined by experience.  I will give to a common plate about four seconds, an orthochromatic plate under the same conditions five seconds.

The yellow glass screen is prepared as follows:  Take a piece of best plate glass—­common cannot be used—­clean it nicely; take another large plate glass, or anything that is level and true, level it with a small spirit-level.  Now take the cleaned piece of glass and coat it with

AURENTIA COLLODION.

Ether                                  5 oz. 
Alcohol                                5 oz. 
Cotton                                60 grs.

The aurentia to be added to suit your judgment; it takes a very small quantity to make an intense yellowish-red collodion.  Pour it on the center of the glass, flow it to the edges, and before it sets place it on the level glass and allow it to set; when set put it in a rack to dry.

Should it dry in ridges, the collodion may be too thick, and it must be thinned down with equal parts of alcohol and ether.  A single piece of plate glass, about one-eighth inch thick, coated with aurentia collodion, is all that is required with an erythrosine plate.  Or, after a piece has been successfully coated, another piece of the same plate glass, and the same size, may be cemented together with balsam, having the coated aurentia side between the two glasses; the edges may then be bound with paper.