The Dictionary Of Photography

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

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Clearing Bath
a reduced representation of a landscape with subdued tints ; but perhaps more specially useful to landscape photographers in this respect.
Clearing Bath. Any solution used to clear or cleanse a negative or positive from the stains of development is thus termed. The following are those in most common use : -
Alum           ... ... ... ... ... 2 ozs.
Citric acid   ... .., ... ... ... I oz.
Water          ...............      20 ozs.
Or
Chrome alum         ... ... ... ... 1 oz.
Citric acid.............. 1 ,,
Water          ... ... ... ... ...      20 ozs.
The latter is specially useful, the chrome alum having a special tanning action on the film much superior to ordinary alum. The addition of a little ferrous sulphate has been recommended, but without any notable benefit. When plates are developed by pyrogallol and soda, a very non-actinic yellow colour is given to the film, which protracts the operation of printing most in-ordinately. By use of the chrome alum bath this colour is changed to fine olive green, which scarcely effects the printing. In the case of ferrous-oxalate development the same bath is useful for clearing off the deposit of oxalate of lime due to the use of hard water, whether on negatives, positives, opals, or paper. Mr. B. J. Edwards has suggested the following, which, as it possesses one or two features distinct from the others, is here given : -
I.
Alum.................. 1 oz.
Citric acid ... ............ 1 ,,
Water           ............... 15 ..
II.
Saturated solution of sulphate of iron ... 5 ozs.
For ordinary use one part No. II. is mixed with three parts of No. I. If the negative is a little too dense, the use of No. I. solution alone will reduce the same. If not quite dense enough, the use of No. II. alone will often give the slight effect required to pro-duce a satisfactory negative. Mr. Edwards recommends the use
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