Well-sized fine glazed papers generally adhere least, and are usually laid on dry. When the impressions are to be issued without glaze very thin fine-surfaced cardboard—not enamelled—is frequently used, and the margin of the printing plate covered with a suitable mask. Any well-sized paper possessing a fine surface may be used. Impressions on such paper may be passed through a weak solution of gelatine, and after drying, rolled, varnished, mounted and again rolled. Any retouching must be done immediately after the sizing, and before the application of the varnish. Enamelled papers require a special glaze, not a lacquer, or are finished without glaze at all. CHAPTER VI. PREPARATION OF THE COLLOTYPE PLATE. The well-polished glass plate must be thoroughly cleaned with alcohol and ammonia, and it should be ascertained that the surface is entirely free from scratches. It is then coated with the substratum, consisting of a dilute solution of silicate of soda and albumen. The following formula is in constant use by many practical workers of experience, and answers every requirement:— Distilled water 8 parts. White of egg—whisked 7 ” Silicate of soda (of the consistency of syrup) 3 ” This mixture should be well beaten to a froth or put in a bottle with pieces of broken glass, well shaken, and placed aside to settle for half-a-day. Then filter through paper, which should be replaced so soon as the pores become choked. To facilitate the operation the filter paper should before use be moistened with distilled water. The surface of the plate should be flooded with water, and coated as evenly as possible with the above solution, a small glass rod being made use of to assist the flow. Air bubbles must be removed, and by quickly tilting the plate the superfluous solution run off; this should not be used to coat other plates without being again carefully filtered. If the substratum be thin, it is not necessary to wash the plate after drying, but after standing aside two days to harden, with dusting and warming, they may be coated with the chromated solution of gelatine. If small crystal formations appear on the surface the plate should be well washed and again dried before proceeding further. The following formula for substratum is due to M. Thiel, senior; it contains less silicate, and the washing before applying the sensitive coating is never necessary:— Distilled water 36 parts. White of egg 20 ” Silicate of soda 6·2 ”