Thomas Rodger of St Andrews
By Rob Douglas | Published
Thomas Rodger was the protoge of Dr John Adamson of St Andrews . He learnt his photography at the hand of this master of the art from the age of 14 and rapidly gained a reputation as an expert in manipulating the chemistry of the volatile Calotype process as well as the daguerreotype. At the age of 17 he set up his first studio in St Andrews after being persuaded to become a professional photographer by Dr John. His first studio was described as a shed , but from humble beginnings he went on to great things . If you wish to see more from this great photographer then the St Andrews web site is a great place to start . www.st-andrews.ac.uk/imu/imu.php?request=browse&irn=1295 Excerpt from On Collodion Calotypes by Thomas Rodger. We will now go on to the process of transferring to paper impressions from negative pictures, which, although decidedly more simple and more easily conducted than the previous process, is, nevertheless, often attended with very unsatisfactory results. Various kinds of paper are suitable for obtaining copies — of these some are better adapted than others. I use several kinds, but at present almost exclusively a paper manufactured by Pirie and Sons. One of the specimens, marked No. 3, is on a cream-coloured wove paper, made by Cowan of Edinburgh ; and No. 1 is on Turner's photographic paper, procured from W. and J. Milne, Hanover Street, Edinburgh. Having got a paper fit for the purpose, the first thing to be done, before applying the blackening agent, is to imbue it with some of the metallic chlorides. A solution of one salt may be used, or a combination of two or more. I use a mixture of two chlorides — viz., terchloride of gold and chloride of sodium, of the following strength : — Chloride of sodium, 50 grains. Solution terchloride of gold, 30 drops. Rain water (pure), 20 ounces. The strength of the solution of terchloride of gold is 15 grains of the crystallized chloride to 4 drams of distilled water. This solution being put into a shallow dish of a size suit able for the sheets of paper, they are taken one at a time by two adjacent corners, and are slowly drawn through the solution, first one way and then the other. They are then pinned by one corner on a wooden screen to dry. Total render this paper sensitive to light, I pursue the following method : — Taking a piece of the paper, and driving off any dampness it may have contracted by slightly warming it, I then proceed, with a glass rod or a pellet of cotton, to coat its surface with ammonio-nitrate of silver as evenly as possible, and then dry it quickly, by holding it to the fire, or by pinning it up in a dry, darkish place. Dampness, either before or after the sheet is coated, is very apt to cause blotches, and hence it is advisable to use the sheet as soon as possible after it has been prepared. The pressure frame I use is of the simplest construction. It consists merely of a cross-headed flat board, to which is attached by hinges a frame containing a square of plate glass ; the pressure being given by a pinching screw. The ammonio-nitrate of silver is made as follows : — Nitrate of silver (crystallized), 110 grains. Rain water (pure), 3 ounces. Shake till all the crystals are dissolved, and then add liquor ammoniae (fortissimus) in small quantities till the precipitate at first formed is almost entirely redissolved. Should too much ammonia be added, a few crystals of nitrate of silver will bring back the turbidity, in which condition I find it most suitable. When the negative and sensitive sheet of paper underneath have been exposed to the action of the sun's rays long enough to make the copy a shade or two darker than it is intended to be when finished, the copy should be immersed as soon as possible into a bath of hyposulphite of soda to prevent the light from exerting any further influence upon it, or, as it is termed, to fix it. This bath is made thus : — Hyposulphite of soda, 2 ounces. Water (common), 16 ounces. To render this bath from the first capable of giving tints equal to an old bath, there should be added a dram or half a dram of chloride of silver, and 40 drops of chloride of gold solution, of the strength already mentioned. Those pictures, which were from the first rather faint, will be fixed after ten minutes' immersion ; and darker ones may be allowed to remain as many hours, or until they assume the desired gradation of light and shadow. The pictures must then be subjected to a thorough washing, so as to remove completely all traces of the hyposulphite of soda bath, which will otherwise be pernicious to the permanence of the colours of the photograph. The copies are then dried ; and pressed, or polished on the back, I have thus endeavoured shortly to describe the manner in which I practise the calotype process, and which I can confidently recommend for certainty and success. I have only given an account of one process, although several others might have been mentioned, being anxious not to confuse or render the description unnecessarily complicated. The adjustment of the chemical materials to each other is of such importance, that the greatest accuracy is required in their preparation. All the manipulations of the process also require the greatest care. In conclusion, I trust that my description is sufficiently clear to be understood, and that it may be of use in forwarding the progress of this art, and that it will be followed by accounts of the experience of others. Chloride of sodium, 50 grains. Solution terchloride of gold, 30 drops. Rain water (pure), 20 ounces. The strength of the solution of terchloride of gold is 15 grains of the crystallized chloride to 4 drams of distilled water.(very very strong). 3.24 grams sodium chloride. 568mill distilled water. 0.57% . The strength of the solution of terchloride of gold is 15 grains of the crystallized chloride to 4 drams of distilled water. 0.97grams gold chloride dissolved in 14.20mill of distilled water = 6.83% = 36 drops per 100mill dh2o. The ammonio-nitrate of silver is made as follows : — Nitrate of silver (crystallized), 110 grains. Rain water (pure), 3 ounces. Adding strong ammonia until the liquid clears . Slightly turbid is better . 7.13 gr silver nitrate in 85.23 mill dh2o. 8.37%. Hyposulphite of soda, 2 ounces. Water (common), 16 ounces. To render this bath from the first capable of giving tints equal to an old bath, there should be added a dram or half a dram of chloride of silver, and 40 drops of chloride of gold solution, 62.2 grams of sodium thiosulphate in 454mill water . 13.7% Gold chloride . = 60drops per 100 mill. 1.95 grams or 3.88 grams silver chloride .425% to .85% .