The Dictionary Of Photography

A True Historic Record Of The Art & Practice Of Photography 100 Years Ago.

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Backing Plates
are two long lengths of bamboo carrying a point at each end, these serving to support the background against a wall as shown in the sketch (Fig. 14), the lower points engaging slightly in the floor so as to hinder them from slipping outwards. For porta-bility, the two long lengths which serve the double purpose of
struts and supports may be divided and furnished with a socket-joint at D. (Also see Portraiture.)
Backing Plates consists of coating the back of plates with some black or non-actinic substance to prevent Halation (q.v.). The essentials of a perfect backing are that it should reflect no rays of light - or, at least, only those that are non-actinic - and that it should be in absolute optical contact with the back of plate. Several methods have been recommended, coating the back of the plate with collodion stained with aurin or any non-actinic dye being a method which is easier advised than done in the dim light of the dark-room. The following, if spread upon brown paper and damped before applying to the plate, answers well: -
Powdered burnt sienna
Gum.........
Glycerine ......
Water.........
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