DEVELOPING AND FIXING COMBINED A system of developing in which a sufficient amount of " hypo " is mixed with the developer in order that developing and fixing may be per formed at the same time, a method thought much of at one time but little used nowadays. The secret of successful work is in the use of the correct amount of " hypo " to balance the developer. The " hypo " may be mixed separ ately and added to a developer, or made up in the developer itself. For the latter method edinol is perhaps the most suitable : Sodium hyposulphite 15o grs. 26 g.
Sodium carbonate . oz. 62•5 „ Sodium sulphite . 30o grs. ,, Vino' . . . oz. 21 „ Dissolve the first three in iz oz. of water, add the edinol, and use at once. The former method is to make up the " hypo " and developer proper separately and mix before use, as follows :— Ordinary developer . 5 oz. 15o ccs.
Sodium hyposulphite sol. (20 %) 2 or 3 drops The following developer is one that is popular upon the Continent, and works well with "hypo " :— Hydroquinone . 6o grs. 8.5 g.
Metol . . 30 „ IP Sodium sulphite ,, Sodium carbonate 600 „ ,, Water to . . 16 oz. Imo ccs.
The " hypo " solution is added in the proportions stated above immediately before use.
If properly mixed, development is at the time the plate is fixed, and the negative simply requires the usual washing. The method forms an interesting experiment, but is not recom mended for valuable exposures, as with some plates it does not always work so well as could be wished. " Hypo " also acts as an acceler ator with some developers. (See " Hypo in Developer.") Kachin is one of the most suitable developers for combination with " hypo." J. McIntosh advocates the following : A. Kachin . . 6o grs. 15-5 g.
Sodium sulphite . 600 „ '55 ,, Water to . . 8 oz. 1,000 ccs.
B. Caustic soda . 40 grs. 18 g.
Water to . . 5 oz. Imo ccs.
C. Sodium hyposul phite . . i oz. 50o g.
Water to . . 2 „ 1,000 ccs.
For use take of A 160 minims, B 240 minims, C 20 minims, and water to make 1 oz.