(I) F. C. Beach presented the following formula for reducing negatives: -
(a) Water ...... 15 dr.
Water ...... 8 oz.
Potassium cyanide .. 10 gr.
The plate to be reduced is soaked in water for a minute, and is then flowed over with (a) for 1/2 minute; it is then washed, and flowed with the cyanide solution. The reduction takes place gradually, and if the first application is insufficient, the operation should be repeated.
(2) A formula given by Newton is as follows: -
Water ...... 10 oz.
After the copper is dissolved :
Potassium bromide .. 100 gr. are added, which converts the solution into copper bromide.
Then 1 oz. of the above is added to 2 oz. water; the plate is soaked in this for a minute or two, washed, and put into a weak solution of soda hyposulphite for 2-3 minutes, and again washed. The manipulation may be repeated should the reduction be insufficient. The copper solution may be used over and over.
(3) Another solution is: -
Water.......... 1 oz.
Iron perchloride solution, as obtained at the druggists' 1/2 dr.
The plate is laid in this for 2-3 minutes, washed, put into a weak solution of hypo for the same length of time, washed, and dried. (4) It is often observed that there is no satisfactory method of reducing mercury intensified negatives. This assertion requires qualifying. When the silver cyanide method is adopted, the mode of operation is extremely simple. The only danger is of overdoing it, and allowance must be made for the difference between a gelatine negative when in a wet and a dry state.
If a negative be too dense when removed from the silver cyanide bath, flow over it a weak solution - say 2 oz. of a saturated solution to 1 pint water - of soda hyposulphite. The action which follows is a rapid one, and a second or two sometimes suffices to produce the requisite effect. Water should be handy, into which the negative should immediately be plunged and well rinsed before examining it. It will now be found more harmonious, and the colour unchanged, excepting in so far the now thinner film. If the reduction be insufficient, the operation can be repeated. The negative requires, of course, to be well washed afterwards to free it from hypo.
As to the keeping qualities of negatives so reduced, if the primary operations of fixing and thorough washing be properly performed, there is no difference from other negatives not so treated.
Should a negative that has been intensified and varnished be found to give hard prints, the varnish can be removed, and the operation of reduction performed in a similar manner. To remove the varnish, flow over the negative sufficient methylated spirit to cover it. Allow the spirit to remain for a little to penetrate the varnish. Drain on to a tuft of cotton wool, then gently polish, so to speak, the face of the film. Once more flow with spirit, and clear off with a soft piece of clean linen rag. Afterwards immerse in water, when any gum still adhering is easily removed, and the negative is ready to be reduced. (A. Donald.)
(5) A formula given by Dr. Janeway consists in dissolving 9 gr. potassium ferricyanide (red prussiate of potash), by stirring with a glass rod, in 3 os. of a 5 per cent. solution of soda hyposulphite, which is sufficient to cover a 5 X 8 plate, and should be mixed on the day it is used. The action of the reducer is quick, and careful watching is necessary. With a camel-hair brush, which has been dipped in the solution, dense portions of a dry negative may be touched over and reduced. Care should be taken to wash off the plate after each application.