If blisters make their appearance it is probable, if the substratum be of albumen, that the solution is not sufficiently dilute. With some hinds of india-rubber blisters always appear. The practice of tacking prints on the wall with a coal hammer is another prolific cause of blisters.

Transparent Markings

Transparent Markings - may be caused by handling the subject with warm fingers before immersion in water previous to development. Handling with cold fingers has its own problems.

A Transparent Edge

A Transparent Edge - will be caused by allowing the whole length of the edge of the subject to rest on blotting paper when drying in the drying-box. The only consolation is that some subjects look better with transparent edges. A lack of density - is caused by the collodion being too thin, requiring more pyroxyline; by an insufficient quantity of iodide; by insufficient sensitizing in the bath; or by too weak an alkaline developer. Keeping the subject at school until Matric has been passed can only be regarded as a secondary cause. Lines - may be caused by a stoppage in the wave of developing solution, by removing the subject in the drying-box previous to complete dessication, or by an uneven flow of preservative over the film. It is therefore a fallacy to assume that old-age and late nights are the only causes of this prevalent phenomenon. Black spots - on the film may be due to the india-rubber substratum, and to dust on the plate. They are sometimes due to indigestion, in which case they do not remain stationary, but move slowly in an oblique direction.

Transparent Spots

Transparent Spots - may be met with when photographing near the sea. {See lace insertions in bathing costume of subject standing by portable dark room, on opp. page). They are probably due to the chloride of sodium which is held in suspension in the air. They rarely occur if the subject has been thoroughly dried finally by artificial heat a short time before exposure. Many students regard this drying-out process as one of the best things about seaside photography. Pinholes - may be caused by the solution of silver added to the developer dissolving out iodide from the film. If the preservative be not well filtered such defect may likewise occur. Blast pinholes! If the preservative used for the dry plate contains any substance only slightly soluble in the former, but more readily in the latter, then the latter should be flowed over the subject and allowed thoroughly to permeate the surface. A good washing under the tap afterwards is then necessary. If the preservative contains nothing soluble by alcohol, water should be applied in the first instance. Quite a lot of defects can be traced to the too exclusive application of alcohol, regardless of solubility.

Transparent Spots UncleAlbertsManualOfPracticalPhotography 60

Whether spirits of wine or water be the agent used for softening the film, great care should be taken that there is no stoppage in the flow, otherwise markings in the negative may become apparent. (A dipping bath or a flat dish is useful when water is to be applied.) The preservative must in all cases be eliminated from the film as far as possible before development commences.