10. _Marks from the developer not running up to the edge of the film_ (p. 212). Remedy this as far as possible by allowing the Collodion to set a little more firmly before dipping the plate in the Bath. IMPERFECTIONS IN COLLODION NEGATIVES. 1. _A want of Intensity._--a. From the development not having been sufficiently pushed (p. 224).--_b._ From the Collodion film being too blue and transparent for Negatives.--_c._ The Collodion newly made from pure materials (p. 114).--_d._ The plate kept too long between exciting and development (p. 100).--_e._ The Bath newly prepared from commercial crystallized Nitrate of Silver (p. 101).--_f._ The light too feeble, as on very dark wintry days, or in copying interiors, etc. 2. _Inferior half-tones, with great intensity of the high Lights._--_a._ From the plate being insufficiently exposed.--_b._ The Collodion of inferior quality, either too strongly tinted with Iodine or made from impure materials.--_c._ The Nitrate Bath old and partially decomposed.--_d._ The light reflected too strongly from the object. When the light is unusually bright, a feeble Collodion and a newly mixed Nitrate Bath will be found to give better definition in the high lights than an intense Collodion, which may produce chalky Negatives. 3. _The image pale and misty._--The plate is over-exposed (if so, the image will probably be a reddish-brown colour by transmitted light), or there is diffused light in the Camera or developing room. The presence of Bromides or Chlorides in the Collodion may occasionally produce the same effect. 4. _The high lights of the image are solarized._--A change of colour to a light brown or red tint by transmitted light, with a dark shade by reflected light, is favoured by over-exposure of the plate, by organic decomposition of the Collodion, and by Acetate of Silver and other organic bodies in the Bath. 5. _The image dissolves off on applying the Cyanide of Potassium._--The Collodion is probably over-iodized. The same thing may also happen in the Honey preservative process, when the plates have been long kept and the indurated layer of syrup not properly removed before applying the developer. 6. _The developer does not run up to the edge of the film._--This is likely to occur when using Collodion nearly anhydrous; and particularly so with a new Bath not containing much Alcohol. The film will be less repellent, if a longer time be allowed before dipping in the Bath. 7. _The film does not stick to the glass._--Clean the plates very carefully, and make the Collodion a little thinner if required. Allow a longer time before dipping in the Bath. A very effectual plan is to roughen the surface of the plates, about an eighth of an inch round the edges. IMPERFECTIONS IN COLLODION POSITIVES.