1035. Action Of Chemicals On Paper

Action Of Chemicals On Paper. Developing agents such as metol-hydroquinone, ortol, amidol, etc., are used to develop the image. Sulphite of soda is used as a preservative in the developer. Carbonate of soda is used to open the pores of the paper, allowing developing agents to act freely and evenly. Increasing the amount of carbonate increases speed of development. Bromide of potash is a most important chemical in the developer, being used to prevent impure or fogged whites. If only enough bromide is used to insure pure whites, the print will be cold in tone. Increasing the amount of bromide in the developer will increase the amount of olive in the print. Thus, it will be seen that bromide is used for two purposes, namely, insuring clear whites and controlling tone.

1036. Exposure And Development

Exposure And Development. Varying the exposure and development will vary the tone of the resulting print. For instance, an under-exposed print, forced in development, will be cold or blue in tone when compared to a fully timed print that develops to the desired depth freely, even though the same developer is used for both prints.

1037. Safe Light For Handling Paper

Safe Light For Handling Paper. The slower brands of Artura paper may be handled in yellow artificial light without danger of fogging. Development may be carried on at a distance of six feet from a 16 candle-power incandescent electric light, or other yellow artificial light of about the same strength, without danger of fogging. The dry paper, of course, should not be exposed to the direct rays of such a light for too long a time. Be sure that the light in the printing room is safe. A test may be made as follows: Allow a piece of paper to lay exposed for the length of time necessary to handle it during manipulation. This piece of paper may then be developed and if the whites show fog, the light in the printing room is not safe. If the whites remain pure, the light is safe. Carbon Black, the fastest brand of Artura paper, must be handled in red or orange light, it being extremely sensitive.

1038. Stock Hardener

Stock Hardener. The hardener used in the fixing bath may be mixed in large quantities, as it keeps indefinitely. A new fixing bath may be mixed at any time by simply dissolving the hypo in water, adding the proper amount of hardener.

1039. Practice Work

Practice Work. Your previous experience with other gaslight papers will, of course, assist you wonderfully in the manipulation of Artura, for you will more readily understand the manipulation and can work more intelligently than if you had no previous instruction. For your first experiments better results will be obtained if the instruction given herein is followed to the letter. As there are different grades and surfaces of Artura paper, for your practice work take them up in their regular order and observe each step of procedure. With "Artura " particularly, you should observe all failures and note all data pertaining to their production on the back of the print. If you meet with failures in any department, consult the General Information department following the lesson, where you will most likely find a remedy, and after a few experiments, you will be able to produce really beautiful results. Prints from all your first efforts with each grade of paper should be preserved, as your first work will be a guide to advancement. Carefully note all data pertaining to manipulations from beginning to end. Note these on the back of each print, preserving them in your proof file. They will prove to be a splendid reference and assistance for future guidance.

1039a. M-Q Developer and Its Composition. - The chemicals used in the Metol-Hydroquinon developer should be dissolved in the order given in the formula.