This section is from the "Studio Light Incorporating The Aristo Eagle - The Artura Bulletin 1922 " book, by Aristo Motto. Also see Amazon: Studio Light Incorporating The Aristo Eagle - The Artura Bulletin 1922 .
IT is important for the photographer to know that proper precautions are being taken with his work in hot weather. Aside from any monetary loss, his reputation is at stake.
He cannot afford to have negatives or prints spoiled much less have prints deteriorate after they are in the hands of his customers.
The workman cannot afford to have a blot on his reputation because of carelessness or lack of knowledge of the action of the chemicals that go together to make such an important solution as a fixing bath.
A fixing bath may be ruined if it is allowed to become warm, so it is important that the workman have a thorough knowledge of the peculiarities of the ordinary acid fixing bath, especially during the hot summer months.
The Acid Fixing Bath is recommended because there is no better, cleaner-working fixing bath for developing-out papers. And there is no one photographic solution that is more abused. As a result a large portion of the photographer's hot weather troubles can be traced to the fixing bath, though they are often blamed upon perfectly good material.
The purpose of the acid fixing bath is to keep the print hard and firm; to stop development; to prevent developer stains and to fix the print. It will do all of these things if it is properly compounded, is in good condition and not exhausted.
One of the principal fixing troubles is caused by an exhausted bath. And exhausted baths are often used because they remain clear even after they have been used for as many prints as the hypo in the solution can be depended upon to fix thoroughly.
Sixty-four ounces of acid fixing bath should never be used for more than the equivalent of two gross of cabinet prints which would be approximately six dozen 8 x 10 prints.
The only way to be certain is to chalk up the number of prints a given amount of bath will fix and then chalk up the number of prints as they go into the bath. A slate or a pad of paper attached to the wall over the fixing bath facilitates keeping an accurate check on the condition of the bath. Make up a fresh fixing bath as soon as the one you are using nears the danger point, which should be while the bath is still perfectly clear.
This is really important as the bath will not fix prints thoroughly after the hypo has reached the point of exhaustion caused by fixing the full number of prints specified above. This applies to all developing-out papers.
Nothing is more uncertain than an improperly fixed print. You usually learn of the injury too late to make amends. The print may look all right when you deliver it to your customer but later on its weakness develops. The highlights yellow first and if it has had very little fixing the entire print may discolor.
There are many causes of fixing bath troubles and to avoid them one should begin by properly compounding the bath. The easy way to make an acid fixing bath is to make up a stock solution of hardener and then to make a fresh fixing bath for every batch of prints or for every day's work.
Water...... 80 ozs.
Sodium Sulphite(E.K.Co.) 16 ozs. Acetic Acid (28% pure) . 48 ozs. Powdered Alum . . .16 ozs.
Dissolve the chemicals in the order named.
In all formulas it is important to dissolve the chemicals in the order named but it is especially important in making the hardener solution.
If the alum is added to the dissolved sulphite before adding the acid, a precipitate of aluminum sulphite is formed which it is very difficult to get into solution again.
Be sure the sodium sulphite is thoroughly dissolved, then add the 28% acetic acid and then the alum. Some photographers prefer to dissolve their chemicals separately and then to combine them but in combining such solutions the acid should always be added to the sulphite before the alum.
To make a fixing bath, thoroughly dissolve 16 ounces of hypo in 64 ounces of water, and when sure that the hypo is dissolved, add 8 ounces of the above hardener.
If the hypo is Dot thoroughly dissolved the addition of the hardener is likely to make the bath milky. If the bath is milky it is an indication that sulphur has been released, and with sulphur released the solution becomes a toning as well as a fixing bath.
Portrait Film Negative, Portrait Bromide Print By Manning Bros. Detroit, Mich.
The addition of any acid (with the exception of sulphurous) to plain hypo will release sulphur. Alum will do the same but not in the presence of acetic acid and sodium sulphite.
The alum is the hardening agent, the acetic acid the clearing agent and arrestor of development and the sodium sulphite in combination with acetic acid is the preservative. The bath serves three purposes and the chemicals used are dependent upon one another and their proper combination to produce the three results and at the same time retain their balance until the fixing property of the bath is exhausted.
Few of us stop to think of the very complicated chemical action of this apparently simple bath and as a result it is greatly abused. But it is worth even further study if the best and most permanent prints are to be secured.
Prints could be developed, rinsed in a short stop and clearing bath of acetic acid, fixed in a plain hypo bath and hardened in an alum bath. But the acid fixing bath shortens the operation and does the work better and more economically.
The chemical action of sodium sulphite and acetic acid in preventing the release of sulphur from the sodium hyposulphite is due to the fact that any sulphur which is formed combines with the sulphite to again form hypo. In fact hypo is prepared commercially in this way by boiling together sodium sulphite and sulphur.