306. Backed Prints Turning Yellow In Spots

Backed Prints Turning Yellow In Spots. Unless the backing paper has been thoroughly washed to eliminate all the acid in the collodion emulsion, this is apt to occur.

307. Yellow Streaks

Yellow Streaks. (a) Sometimes it is caused by stacking the prints on the bottom of the tray in the first wash water without thoroughly wetting the entire lot of prints.

(b) By using the tray for first washing that was used for washing after the prints came from the hypo fixing bath.

(c) Not picking the prints over and over during the entire manipulation, more especially in the first wash water immediately after fixing.

308. Pink Whites

Pink Whites. Toning too fast or using a gold toning bath which is not sufficiently alkaline. Using extremely cold water for the preliminary washing. Cold water prevents the eliminating of the acid preservative and causes an acid reaction in the gold bath. Adding fresh gold to the bath without first neutralizing it. Using platinum bath that is not sufficiently acid. But the chief cause of pink whites is lack of alkali in the gold bath. This trouble does not usually show until the prints go into the platinum bath. Usually the pink whites are overcome by the sulphite bath previous to fixing, and the pink is entirely removed.

309. Black Spots

Black Spots. Black spots are generally caused by rust or some metallic substance in the water. If the plumbing is old a great deal of rust will come from the pipes and the water should be carefully filtered. They are also oftentimes caused by using metal cut-outs. In trimming oval prints before toning, small particles of metal from the cut-out are apt to adhere to the prints, and when they go into the water not only make a spot on the oval prints, but are often transferred to other prints. Brushing the prints carefully after trimming, or trimming after they are toned, will enable you to overcome this.

310. Prints Fading - (a) Insufficient preliminary washings and improper toning in gold bath. If the print is not thoroughly washed the gold is deposited on this free silver and you are not producing a true gold tone, as it washes away in subsequent baths.

(b) Improperly balanced gold bath, not alkaline enough to allow the shadows to tone.

(c) An over-acid platinum bath. The acid eating into the shadows instead of toning or depositing the platinum salts onto the print. An over-acid bath is caused by using too much old platinum bath. When bath is weak, the adding of acid to make prints tone. Trying to tone too many prints with amount of platinum employed.

(d) Not washing prints sufficiently after platinum bath, thereby carrying acid into the hypo and causing sulphurization.

(e) Using a hypo bath too strong thus eating out the print instead of fixing it.

(f) Insufficient final washing, leaving hypo in prints, which will cause them to fade.

(g) Not allowing air to circulate through the freshly mounted prints, permitting the chemical in the pulp of mount - and acid coloring of same - to destroy the print by prolonged dampness.

(h) Using sour or acid paste.

(i) Prints, after mounted, drying too slowly; or stacking them up too soon. We have found that even when a fresh paste is used under the above conditions, the paste between the print and the cardboard will turn sour and the paste will, as a rule, fade the prints.

(j) Frequently the fading of a print is due to the hypo in the print or the mount. Many of the cheap grades of cardboard are bleached with hypo, which has never been eliminated. A good plan is to test your mounts, and also the last wash water, to see whether they are entirely free of hypo.



16 ozs.

Caustic Soda................................

15 grs.

Permanganate of Potash.............................

3 grs.

312. This will give you a pink solution. To test your mounts or card stock, tear the card in small pieces and soak it in distilled water for ten hours. Then pour in your graduate a few ounces of this water in which the card has been soaking, adding to it a little of your permanganate solution. If there is hypo present the pink solution will change to a green. In testing the last wash water, after fixing to insure permanency, simply pour a little of this into your graduate and add the permanganate, as above. If there is any hypo present it will turn green.

313. A mount or print may contain a certain amount of hypo, or acid, and while the mount is thoroughly dry the presence of the hypo will not materially affect the print. But, if the mount becomes moist or damp, the hypo will work up into the print and cause it to bleach, or fade.