918. Fixing

Fixing. After development is finished, the lantern-slide (for such it now may be called) must be rinsed under the tap and placed in the hypo. An acid hypo should always be used for slides, because it is important to avoid any chance of developer stain.

919. Preparing Acid Hypo Bath

Preparing Acid Hypo Bath. Prepare the following solution:

Sulphite of Soda ............................

2

ozs.

Water........................................

1/2

pt.

When this is dissolved, add 2 drams of Sulphuric Acid C. P. Place this in a bottle and mark it Acid Hypo Stock Solution No. 1.

920. Next dissolve 7 oz. of hypo in 16 oz. of water, and add to this from one to two ounces of stock solution No. 1. This will give an Acid Hypo bath, in which the slides will fix in from three to four minutes. It will be better, however, to allow the slides to remain ten minutes as this will produce clearness and permanency. After fixing, the slides should be washed even more thoroughly than the regular negatives.

921. Another very good formula for a fixing bath is made up in two solutions.

Solution A:

Water .........................

32,

ozs.

Hypo.......................

1/2

lb.

Sulphite of Soda ............................

2

ozs.

Solution B:

Water ...............................

16

ozs.

Chrome-alum ........................

3/4

oz.

Sulphuric acid ( conc.) ........................................

1/2

dr.

While stirring Solution A vigorously, pour in Solution B very slowly. This bath has exceptional keeping qualities, but should be filtered occasionally.

922. Clearing Solution

Clearing Solution. All transparency plates should be put through a clearing solution after fixing and washing. Even though they appear of the right tone and color when wet, they sometimes dry up with a veil. The Clearing Solution will prevent this, and should be made up as follows: First prepare a saturated solution of Alum and a saturated solution of Citric Acid. Pour into your gradu-ate 4 ounces of the saturated solution of Alum, and 4 ounces of the saturated solution of Citric Acid, adding to this one dram of Hydrochloric Acid. Place the transparency in a clean dish and pour the Clearing Solution over it. Rock the tray gently for a couple of minutes; then wash the plate carefully for ten minutes in running water, or give it a dozen changes, of two minutes each, in clear water. A more simple clearing bath, which is equally as good, will be found in lesson on Reducing, Vol. II.

923. Care must be taken not to scratch or injure the film in any way, or the plate will be unfit for use, as these defects are magnified many times when projected on a screen.

924. When washing the slides in running water, be careful that the stream is not too strong, as it is apt to injure the very delicate film on the transparency.