A separate exposure to a very fine stochastic or hard-dot mezzotint screen is made, or alternatively an aquatint grain of asphaltum or rosin is applied and fused to the copperplate usually before the exposed gelatin tissue is adhered to the plate. The UV light travels through the positive and screen (if used) in succession, each time hardening the gelatin in proportion to the degree of light exposed to it. The fourth stage is to adhere the exposed tissue to the copper plate. The gelatin tissue is adhered or "laid down" onto the highly polished copper plate under a layer of cool water. It is squeezed into place and the excess water is wiped clear. Once adhered, the fifth stage is to use a hot water bath to remove the paper backing and to wash away the softer, unexposed gelatin. The remaining depth of hardened gelatin is relative to the exposure. This layer of hardened gelatin forms a contoured resist on the copper plate. The resist is dried, and the edges and back of the copper are stopped out (staged). The sixth stage is to etch the plate in a series of ferric chloride baths, from the densest to slightly more dilute, in steps. The density of these baths is measured in degrees Baumé. The ferric chloride migrates through the gelatin, etching the shadows and blacks under the thinnest areas first. The etching progresses through the tonal scale from dark to light as the plate is moved to successively more dilute baths of ferric chloride. The image is etched onto the copperplate by the ferric chloride, creating a gravure plate with tiny "wells" of varying depth to hold ink. The pattern formed by the aquatint grain or the screen exposure creates minute "lands" around which the etching occurs, giving the copperplate the tooth to hold ink. The "wells" which hold the ink vary in depth, a unique aspect of photogravure. The final stage is to print the cleaned plate. Printing the plate Printing a photogravure is similar to printing any other intaglio plate, especially a finely etched aquatint. A stiff, oily intaglio printing ink is applied to the whole surface of the plate with a rubber brayer, or a small, stiff squeegee, or a rolled tamper. The plate is then gently wiped with tarlatans to remove the excess ink and drive it into the recesses (wells). It is finally wiped with