board, then pin down the sheet to be coated. The sensitising solution is now brushed smoothly over the paper by means of a long-haired, flat, hog-hair brush, after which the sheet is hung up to dry. Hanging up over night in a room where there has been a fire is a convenient plan; but care must be taken to sufficiently close the room against the morning light, as a very slight light fog on the ozotype paper tends to grow or increase if the paper is stored.
Storing the Sensitive Ozotype Paper. Speaking generally the best rule is to sensitise daily as required, but if care be taken not to fog the paper in sensitising, the prepared paper may be preserved for several weeks in a chloride of calcium box. (See Calcium Box or Tube.)
Exposure. The paper is rather more sensitive than the usual silver printing-out papers, and as the brown image is distinctly visible no actinometer is required. Paper which has been kept is rather, more sensitive than ffeshly prepared paper, and the old paper generally gives a softer print than the freshly sensitised paper.
Washing the Sheet. The exposed sheet must be soaked in water until the yellow ground becomes white, but not after this point is reached, otherwise that brown image which is the germ of the future pigment print will begin to deteriorate. After washing the sheets may be allowed to dry, and at this stage the prints may be kept or stored without risk of deterioration.
Pigmenting or Plastering. A transferring solution is pre-pared, and in this considerable latitude is allowable. A pint of water, half to one fluid drachm of acetic acid, 15 to 20 grs. of hydroquinone, and half a drachm of glycerine may be taken as a standard; but from half to one grain of ferrous sulphate is sometimes a useful addition as counteracting a tendency to washing up or bareness in the high lights. In this bath the washed print and a piece of ordinary unsensitised carbon tissue are immersed, and are kept in motion until both are well saturated with the fluid, which may be in 20 or 30 seconds. The sheets are now brought into contact, face to face, while under the fluid and are withdrawn while in contact. The pair is laid on a flat surface, and contact is established by means of a squeegee. The combined sheets should remain in this condition from four to fourteen hours.