=The Wet Collodion Process= is better adapted than any other for the production of suitable negatives, possessing the necessary density and freedom from fog or veil. The bath must work with the utmost cleanliness, and the collodion should not be used too soon after iodising. The developer works better when not quite fresh, and should contain a sufficiency of acid, and the negative, after fixing, should be subjected to a vigorous intensification. Professor Husnik thus comments upon negatives for photo-lithography:— “As in photo-lithography only subjects in black and white line or stipple can be reproduced, to the entire exclusion of half-tone, the negatives should represent the copy by clear lines and opaque spaces. This is seldom the case except in instances where the drawings are specially prepared, and the subjects somewhat bold and coarse. For example, in copying a proof from a fine steel engraving the graduated, grey, hair-lines, appear in the negative somewhat veiled, whereas the intermediate spaces between close shading, and which are somewhat toned in the print, are not developed actually opaque in the negative. On this account the fine hair-lines will take longer to print in the copying-frame than the bolder shadow lines. The latter may develop faultlessly, while the ink may leave the hair-lines. The intermediate spaces between close shading may not be sufficiently opaque in the negative, consequently the print is over-exposed in these portions, and during development remains covered with ink. Such faults must be overcome as far as possible by shading the negative during printing in the usual well-known manner.” =The Colour= and condition of the original copy will greatly influence the class of negative it is possible to obtain, and if allowable it will be advisable =To Bleach= old engravings or other copies, either yellow from age or stained, by immersing them in eau-de-javelle[V] 10 cc., water 100 cc., wash in water for two hours, and finally in a weak solution of hyposulphite of soda. [V] Chloride of lime 1 oz. Water 15 oz. Carbonate of potash 2 ” Water 5 ” Mix the two solutions together, boil, and filter before use.