This section is from the book "Complete Self-Instructing Library Of Practical Photography", by J. B. Schriever. Also available from Amazon: Complete Self-Instructing Library Of Practical Photography.
870. Carbon (Grade A) is a fine velvety matte surface paper especially adapted for work requiring full detail on a matte surface paper. This is furnished in double weight as well as single.
871. Rough (Grade B) has a rough surface grain excellently adapted to show artistic effects in landscapes.
874. Azo paper has a blue body and, therefore, requires a little more bromide to obtain olive black effects. Too small a quantity of bromide will give blue prints. Aside from this, Azo paper is manipulated exactly as Velox.
Developer. Azo paper may be developed with any of the formulae previously given for Velox paper, but the formula recommended for Nepera papers, on a following page, will also serve as a good developer for Azo paper.
Practice Work. Azo paper, besides being a cheaper product, is also coated on a blue body paper, thus giving a little colder tone. Therefore, a little more bromide may be employed in the developing to offset the blue and change to a light olive. The manipulation of Azo is practically the same as Velox, or other gaslight papers. There is one advantage, however, with Azo over the Velox. The grain of the paper appears closer and is, therefore, preferable for small negatives. In fact the results very nearly approach platino, or matte surface printing-out paper. This paper is generally employed in studios for commercial purposes, and uniform results may be obtained with it. For the finer results, we recommend Velox; yet as you should become familiar with the manipulation of the cheaper products, test prints should also be made on Azo and filed, with all data pertaining to production.
Nepera Gaslight Paper. Nepera paper is a superior developing product for use in professional portraiture. It is made with special reference to the requirements of studio photography, and particularly adapted to the average portrait negatives. It can be printed by any light. Nepera is made in one speed and two weights, single and double, and comes in three surfaces, matte, velvet and rough. The surfaces require no description, except that the velvet is semi-gloss. Double weight Nepera is an extremely heavy stock, desirable for unmounted prints or those delivered in folders. Embossed double weight velvet Nepera when re-developed is especially attractive and looks like platinum.