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.
Artura Iris is designed to produce a warm tone - a desirable olive black tone - not green black but olive black, and all photographers who have properly handled Iris know that it does produce that tone and at the same time retain its delicacy and full scale of gradation without loss of detail and blocking in the shadows.
Iris will also produce blue black tones and pure black tones by modified development as explained in the manual "Artura Results."
In producing the olive black tone and avoiding the less desirable greenish black tone, some knowledge of the action of Bromide of Potash in the developer is necessary.
For example, an Iris print developed in regular Artura developer containing no Bromide of Potash will develop up flat and weak, having a grayish or bluish appearance. The development will be rapid and the whites of the print will be degraded - fogged. If the print is allowed to remain in the developer a second or two after the image flashes to its full depth, development will continue rapidly and the entire print will quickly become black. To overcome this, Bromide of Potash is added to the developer, acting as a restrainer of development, protecting the unexposed silver in the print from the action of the developer and thus keeping the highlights and white margins pure white.
When only enough Bromide is used to keep the whites clear the print will be cold in tone.
A slight increase of Bromide will give good blacks and still more Bromide will produce the greenish black, not so desirable, and right here is where the mistake is made.
By R. M. Wilson Pueblo, Colo.
A photographer starting out to produce olive or warm black tones on Iris will mix his developer according to formula or use Artura developer tubes, adding Bromide of Potash as specified. He will then make a trial print and possibly it will be too cold in tone, due to under-exposure or local water conditions which make more Bromide necessary. More Bromide is added and possibly more exposure is given the next print, but the resulting tone is green black, which is not as desirable as the cold black tone previously obtained.
The photographer says to himself, "If I use less Bromide I will get tones too cold to suit me and if I use a little more Bromide I get greenish black tones. I know the added Bromide is causing the greenish tones and yet if I cut it down I fail to get the warm tone I want."
With Artura the rule to follow to produce the desirable warm black is to use plenty of Bromide. Don't stop at the greenish black tone but use enough Bromide to go beyond it into the olive or brownish black tone.
It is not possible to give the exact amount of Bromide of Potash on account of varying conditions. The Iris formula recommending one drop of a saturated solution of Bromide of Potash to each two ounces of developer works well under average conditions, but in some localities the water, due to alkali or other foreign substance, destroys the balance of the bath and more Bromide is necessary.
Forget all you know about the use of Bromide of Potash in connection with the average developing paper, as with Artura Iris a slight excess of Bromide will not cause muddy tones and blocked prints.
of course there is a limit to the amount of Bromide that can be used in making prints on Artura Iris, but many successful users report doubling, tripling and quadrupling the normal amount with very pleasing results.
Plenty of Bromide in the developer will have a tendency to slow the development somewhat, but this is really an advantage as it increases the control of prints during development and at the same time produces an image of fine grain and pleasing warmth.