Choice Of Paper Sizing





In all the photographic processes by precipitation of metallic oxides the

quality of the paper has a great influence on the results. When the paper

is not well sized and not well calendered, the sensitizing solution is

absorbed, instead of simply impregnating the surface of the paper, and not

only the image is sunk in and its sharpness impaired, but good whites can

never be obtained, especially if the image should be toned, owing to the

impossibility of eliminating the metallic salts not acted on, that is, not

reduced by the action of light which the fibers of the paper mechanically

retain.



The "endless" rolls of paper, 54: inches wide--or "blue print paper," as it

is sometimes termed--of Blanchet freres et Kleber, of Rives, better known

as "Rives' paper", that of Johannot, of Annonay (France), and the

Steinbach (Saxe) paper are recommended.



For small prints from negatives in half tone the positive paper, 18x22

inches, of Rives or Saxe, should be preferred to the heavy kind. It is

advisable to size it, so that the impressions be entirely formed on the

surface of the paper. Moreover, an additional sizing is always

advantageous, whatever be the photographic process employed, to prevent

the imbibition of the sensitizing compound and to obtain more brilliant

and vigorous images, for the iron, chromium, uranium and other metallic

soluble salts require the presence of an organic matter (alcohol, ether,

gum arabic, glucose, caseine, etc.) to be reduced by the agency of light;

and as a consequence, the greater, within certain limits, of course, the

amount of organic matters, and the more thoroughly they are mixed with the

salts, the more sensitive the preparation and the better the results.



Arrowroot is the best sizing for our purposes. Gelatine may be employed,

albumen also, but the coating should be insolubized when applied on the

paper and dry.



Sizing with Arrowroot.--In a porcelain dish diffuse 4 parts of powdered

arrowroot and one part of liquid glucose in 200 parts of distilled or rain

water and dissolve by heat over an alcohol lamp, stirring all the while.

Let the solution boil for an instant, and when the paste is homogeneous

let it cool down and then remove the skin formed on its surface and strain

it through a fine canvas. Now provide with three small sponges free from

gritty matters and cleaned in water, and nail by the four corners, one

over the other, felt size uppermost, as many sheets of paper as you wish

to size on a board somewhat smaller than the paper. This done, with one

of the sponges take a small quantity of the arrowroot and, brushing it

length-way and cross-way, spread the paste into an even layer, then, by

rubbing very lightly with the second sponge, efface the striae and smooth

the coating as well as possible. The third sponge serves to remove the

excess of paste when too much is at first spread on. From six to seven

sheets of paper, 18x22, can be sized with the quantity of arrowroot paste

above given.



Another, but not quite so effective a manner of sizing although sufficient

for the cyanotype, is the following, employed by Mr. Pizzighelli for the

paper used in the platinotypic process:



Ten parts of arrowroot are powdered in a mortar with a little water and

then mixed by small quantities to 800 parts of boiling water. After a few

minutes 200 parts of alcohol are added and the mixture filtered. The

paper is immersed for two or three minutes in the warm solution and hung

up to dry.



Sizing, with Gelatine.--Dissolve at a temperature of about 140 deg. Fahr.

(60 deg. C.) 10 parts of good gelatine in 800 parts of water, then add 200

parts of alcohol and 3 parts of alum dissolved in a little water. Filter

and prepare the paper by immersion as above directed. The gelatinized

paper when dry should be prepared a second time and dried by hanging it up

in the opposite direction in order to obtain an even coating.





Causes Of Failures Cj Burnett's Process 1857 facebooktwittergoogle_plusredditpinterestlinkedinmail

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