Home >> Cyclopedia Of Photography >> Printing In Clouds to Vignetters And Vignetting >> Uranium Printing

Uranium Printing

paper, solution, nitrate and acid

URANIUM PRINTING The first uranium printing processes were worked out by J. C. Burnett (1857-8) and Niepce de Saint Victor, who took out an English patent in 1858. Paper was floated upon a r in 3o solution of uranium nitrate, dried in the dark, exposed under a negative to daylight until a faint image printed out, developed by floating on a bath of silver nitrate (4o grs. to the ounce) or upon a solution of gold chloride (9 grs. to the ounce), then washed and dried. In 1864 a pro cess in which the uranium and silver were mixed with collodion and applied to paper was patented by Wothly. (See " Wothly's Process.") One uranium process has points of similarity with platinotype. Paper is coated with ferrous oxalate in the proportion of I gr. to each square inch of paper, each ounce of the solution contain ing also 1 gr. of mercuric chloride. When dry the paper is exposed in contact with a negative and developed on the following bath : Gold chloride • . 3 grs. • g.

Uranium nitrate • 45 ,, Water . . . 3 oz. 30o ccs.

It is washed, fixed in a weak solution of hydro chloric acid, washed again and dried. Other formulm have been published.

Uranium for Gaslight Printing.—In Dr. J. Bartlett's process (1906), the paper is sized with gelatine containing potash alum and oxalic acid, and sensitised with— Silver nitrate . . 275 grs. 63 g.

Uranium nitrate . 44 oz. 495 ,, Distilled water . . 8 „ 80o ccs.

Float the paper on this bath for three minutes, dry in the dark, and keep free from moisture.

On account of the radiations from uranium it is necessary to prepare and use the sensitive solution in the dark-room. Exposure is made under a negative in the usual way ; with an average negative, from twenty to sixty seconds will be enough at 6 in. or 8 in. from a gas mantle ; one to five seconds to sunlight, and thirty seconds to dull daylight. The print is then developed in the following : Ferrous sulphate . i oz. iio g.

Tartaric acid . . „ 55 , Sulphuric acid . . 6o mins. 12.5 ccs.

Glycerine . . . 6o „ 12.5 „ Water to . . . ro oz. 1,000 „ The image develops rapidly and varies from brown to as& warm black. Should the whites not be pure, due to over-exposure, add tartaric acid to the developer ; the tendency to discolour the whites is entirely prevented by adding a trace of nickel nitrate to the original coating solution, but this renders the paper less sensitive. A rinse in weak acid or plain water completes the process.