A thin layer of this is applied by means of a short, stiff, flat hog's hair brush to the back of the print. It is then allowed to evaporate for a minute or so, and when tacky is applied to the mount, covered with a sheet of glazed paper, and a roller squeegee passed over the surface.
| 15. | Saturated solution of bleached shellac in alcohol. |
This must be applied as thinly as possible.
| 16. | Le Page's fish glue applied to the edges only of the back of the print. |
A fourth method is to first carefully clean the edges of the glass surrounding the print still adhering to it. Then to paste down the mount to the print and let all dry. Then strip the print from the glass now already mounted. This is, however, a process not to be recommended, because requiring a long time for the print to dry, as the evaporation has to take place through the substance of the mount.
ADDITIONAL PROCEDURES WITH P.O.P.
Development of Partially Printed Proofs.—This method of procedure is sometimes a matter of convenience in dull weather, etc. The printing is to be carried on until one can just see a very slight indication of detail in the high-lights. It is then washed in running water for about ten minutes, and then put into a ten per cent. bath of potassium bromide, and there it remains for another ten minutes or so. In this bath some of the image seems to fade away, and generally the print takes on a yellow tinge. The print is next washed in running water for about ten minutes, and then developed with ortol, metol, or preferably, hydroquinone. A considerable variation in the proportions of the constituents of the developer are possible. In general terms, one may say that a developer which gives a good black and white lantern slide when diluted with about an equal quantity of water will give a satisfactory print.
17. As an example of a thoroughly practical developer for this purpose we may give just one example:—
| A | ||
| Hydroquinone | 70 | grains. |
| Potassium metabisulphite | 5 | " |
| Potassium bromide | 30 | " |
| Water | 20 | ounces. |
B | ||
| Soda sulphite | 1 | ounce. |
| Caustic soda | 60 | grains. |
| Water | 20 | ounces. |
Take equal parts and mix just before use, wash for at least ten minutes in running water at once after development.