ANTIMONY PROCESS (Fr., Photographie l'antimoine ; Ger., Spiessglas-Druck) A printing process discovered by Francis Jones, of the Manchester Grammar School, in 1876. When the gas stibine, or antimonietted hydrogen is passed through a glass tube containing sulphur, in the presence of sunlight, a decomposition takes place, resulting in the formation of the orange antimony sulphide :— + 6 S = + 3 Stibine Sulphur Antimony Sulphuretted Sulphide Hydrogen Since no change occurs in the dark, it was found possible to utilise the reaction for photographic purposes. Ordinary writing paper may be treated with a solution of sulphur in carbon disulphide and the solvent allowed to evaporate, the loose grains of sulphur being then gently brushed off the surface with a tuft of cotton wool. A special printing frame is used, having a tube led into the back, so that the gas may be conveyed into the felt with which this is lined in order to impregnate the paper. A fern, a piece of lace, or other suitable object having been placed in the frame and the paper laid over it, the frame is exposed to sunlight, and connection is made with the gas. A print of an orange red colour is quickly produced, the image con sisting of permanent metallic sulphide imbedded in free sulphur. No fixing is required, the gas being simply disconnected when printing is sufficiently advanced. The operation should be
carried out in the open air, care being taken not to inhale the fumes, which are poisonous. To obtain the gas, a small quantity of a solution of antimony trichloride (butter of antimony) is added to any hydrogen generating apparatus, as, for example, a Woulff's bottle furnished with a thistle funnel and a delivery tube, and contain ing dilute sulphuric acid and granulated zinc. The emerging gas then consists of a mixture of antimonietted hydrogen and hydrogen. It is advisable to dry the gas by passing it through calcium chloride tube before leading it into the printing frame. Although of considerable interest, this process appears to have certain disadvantages, which have hitherto prevented its use by the practical worker, not the least of these being that the silver image of a negative begins to be affected by the sulphur after several impressions have been taken.
In process work, there is an antimony process which consists in blackening a zinc plate with a solution of antimony chloride in order that an image transferred to the plate may show up after the plate has been slightly etched. This allows of an artist working on the plate by stopping-out for re-etching.