URANIUM INTENSIFIER An intensifier which gives great additional printing power to thin negatives, the effect not being permanent. A simple formula is :— Uranium nitrate . 4o grs. 9 g.
Potass. ferricyanide . 4o „ 9 ,, Acetic acid . . 27 mins. 6 ccs.
Water . . . ro oz. 1,000 „ A well-washed negative assumes in this a reddish brown colour. It is next briefly washed in water slightly acidified with acetic acid, and finally in plain water until the stain has gone. Any " hypo " left in the film will produce red stains, while any iron in the water, say rust from the waterpipes, will produce blue ones. The inten sification may easily be removed by placing the negative in a weak solution of sodium carbonate or in ammonia, or by prolonged washing. The negative may be treated locally by intensifying the whole in the usual way and working over any parts that are too dense with a camel-hair brush dipped into a weak solution of ammonia and soda. Many other formulm have been recommended, Dr. Liippo Cramer's (used as
above) being noteworthy. The originator claims that his formula, given on the next page, keeps well in the dark and gives a clear image.
Potass. ferricyanide (io % sol.) • 2 parts Uranium nitrate (ro % sol.) . 5 „ Potassium oxalate (lo % sol.) . 5 „ Hydrochloric acid (ro % sol.) . 1 „ Water . . . . . io „ Washing is complete when the stain has dis appeared from the shadow (clear) portions of the negative. When this stain is obstinate and there is a danger of the whole of the intensifica tion being removed by prolonged washing, it is best to apply a 2 per cent. solution of ammonium sulphocyanide. This bath should not be used when the negative is to be worked upon locally with ammonia. Negatives intensified with uranium keep better if varnished, failing which store them in a dry place, not exposed to u strong light.