Part 353

To make a good enlargement five points should be kept constantly in view, viz.:

1. Most careful treatment of the original negative.

2. Making a diapositive complete in all its parts.

3. Scrupulous consideration of the size of the enlargement.

4. Correct exposure during the process of enlargement.

5. The most minute attention to the details of development, including the chemical treatment of the enlarged negative.

The original negative should not be too dense, nor, on the contrary, should it be too thin. If necessary, it should be washed off, or strengthened, as the case may be. Too strong a negative is usually weakened with ammonium persulphate, or the fixing hypo solution is quite sufficient. All spots, points, etc., should be retouched with the pencil and carmine.

The diapositive should be produced by contact in the copying apparatus. A border of black paper should be used to prevent the entry of light from the side.

The correct period of exposure depends upon the thickness of the negative, the source of the light, its distance, etc. Here there is no rule, experience alone must teach.

For developing one should use not too strong a developer. The metol-soda developer is well suited to this work, as it gives especially soft lights and half tones. Avoid too short a development. When the finger laid behind the thickest spot, and held toward the light, can no longer be detected, the negative is dense enough.

The denser negatives should be exposed longer, and the development should be quick, while with thin, light negatives the reverse is true; the exposure should be briefer and the development long, using a strong developer, and if necessary with an addition of potassium bromide.

The silver chloro-bromide diapositive plates, found in the shops, are totally unsuited for enlargements, as they give overdone, hard pictures.

To produce good artistic results in enlarging, the diapositive should be kept soft, even somewhat too thin. It should undergo, also, a thorough retouching. All improvements are easily carried out on the smaller positive or negative pictures. Later on, after the same have been enlarged, corrections are much more difficult and troublesome.

«VARNISHES:»

«Cold Varnish.»—

I.—Pyroxylin 10 grains Amyl alcohol 1 ounce Amyl acetate 1 ounce

Allow to stand, shaking frequently till dissolved. Label: The negative should be thoroughly dried before this solution is applied, which may be done either by flowing it over the solution or with a flat brush. The negative should be placed in a warm place for at least 12 hours to thoroughly dry.

II.—Japanese gold size 1 part Benzol 1 part

Label: In applying this varnish great care should be taken not to use it near a light or open fire. It can be flowed over or brushed on the negative.

«Black Varnish.»—

Brunswick black 1 1⁠/⁠2 ounces Benzol 1 ounce

Label: The varnish should be applied with a brush, care being taken not to use it near a light or open fire. {544}

«Dead Black Varnish.»—

Borax 30 grains Shellac 60 grains Glycerine 30 minims Water 2 ounces

Boil till dissolved, filter, and add aniline black, 120 grains.

Label: Apply the solution with a brush, and repeat when dry if necessary.

«Ordinary Negative Varnish.»—

Gum sandarac 1 ounce Orange shellac 1⁠/⁠2 ounce Castor oil 90 minims Methyl alcohol 1 pint