Manipulation Masks and Discs
crystalline powder. It is used to facilitate the evolution of oxygen from chlorate of potassium.
Manipulation. A term used to express the conduct, the handicraft part, of any operation or process.
Mariotype. (i) A method of carbon printing, introduced by M. Marion in 1873, in which ordinary negatives are used. The exposure can be watched, and Mariotype does not involve transfer in the ordinary sense of the term. Paper is sensitised with a bichromate solution, and after exposure under a negative a sheet of wet bichromated pigment tissue is laid on and pressed in contact. The faint yellow-brown image slowly spreads to the pigment tissue and makes this latter locally insoluble, so that after the original print and the carbon tissue have been in con-tact for some hours, an image like that of an ordinary carbon print may be developed. The mariotype process is easy and practical, but it has been neglected, the inventor having died a few months after its introduction. A paper sized with a 10 per cent, solution of gelatine may be the starting-point. This, when dry, can be sensitised by brushing, dipping, or floating with a saturated solution of bichromate (sodium salt or ammonium salt is more convenient than the potassium salt because more soluble). When dry, the paper is ready for exposure. Ordinary carbon tissue is now soaked in a weak solution of bichromate of potassium (1 to 30 being a convenient strength) and squeegeed down on the brownish image. In a few hours the image may be developed by warm water. For Mr. Manly's new and popular process of direct carbon printing, a process having some affinity with Mariotype, see Ozotype. (2) Another method called mario-type was introduced by M. Marion at the same time as that last mentioned. A sheet of gelatine was exposed under a negative allowed to swell in cold bichromate solution, and contact im-pressions from this sheet were made on ordinary sensitive carbon tissue. These impressions were found to be developable by the ordinary method if the tissue was stored away for a sufficient time.
Masking Skies. See Printing.
Masks and Discs. Pieces of opaque paper used in photo-graphic printing, usually with albumenised paper. In the opaque