This section is from the "Studio Light Incorporating The Aristo Eagle - The Artura Bulletin 1910" book, by Aristo Motto. Also see Amazon: Studio Light Incorporating The Aristo Eagle - The Artura Bulletin 1910.
The tone of Artura Iris, or for that matter Nepera and Bromide papers, depends entirely on development.
Iris having the greatest known latitude in both exposure and development is most easily controlled, and the following, while applicable in a general way to the other papers mentioned, is written with special reference to this peerless brand of Artura:
Taking three prints from the same negative on Artura Iris having different exposures, using normal developer throughout, it will be noticed that the print having the most exposure will have the warmest tone. In making this test the three prints should of course be developed to the same depth.
We will say that the first print is under-exposed and forced in development before it reaches the proper depth. This print will be cold in tone.
The second print is given about normal exposure and develops to the proper depth without forcing. This print will have the normal olive black tone.
The third print is somewhat over-exposed and will reach the proper depth before development is complete. This print will have more warmth or olive black than either of the other two.
Thus it will be seen that the relation of the two factors, exposure and development, determine the tone of the finished print. Normal developer is intended for normal tones, and with normal developer no other tones should be attempted as the quality of the print will be affected.
For cold tones use the developer recommended in the Artura manual "Results." Cold tones are not generally in demand, although in some instances they are desirable. For this reason we will not take up the production of cold tones here.
Normal tones are produced by the use of normal developer, provided prints have been given normal exposure. When prints develop to the stopping point and are then of proper depth, they have been normally exposed.
Warm tones - brownish olive tones are produced by giving more than normal exposure and using an excess of Bromide of Potash in the developer to restrain its action, thus giving the operator full control of the development of the fully timed print. Cutting down the normal amount of Carbonate by at least one-half will also slow the action of the developer.
The exact increase in the amount of Bromide and decrease in Carbonate of Soda to produce the best effects is dependent largely on local conditions and must be decided accordingly.
A good base to start on is to cut the Carbonate down by one-half and use three times the normal amount of Bromide of Potash, always bearing in mind that at least one-third over normal exposure should be given in printing.
Now as to the silver image formed in each case. In the cold or blue black print the deposit of silver is coarse, due to full reduction. In the print of normal tone the image or silver deposit is finer and therefore capable of rendering every delicate gradation. In the full-timed print developed in developer modified as suggested, the silver deposit is exceeding fine grained, and in addition to this fine grain the print is also of a brownish olive tone - a tone that Iris alone will produce and a tone that pleases both the photographer and the customer.
Prove these things to your own satisfaction by working along the lines suggested and you may find that in the full timed, slowly developed print you have a tone even more pleasing to you than the popular normal Iris tone.
Try only a few prints at a time to start with, watching results. After becoming familiar with this method of working it is no different than the regular procedure.
We would not advise taking it up now. During the busy season stick fast to the methods you are using and avoid the possibility of confusion and delay.