52 Weeks of Historical How-To’s, Week 15: The Wet Collodion Process
For this week’s entry of 52-Weeks of Historical How-To’s we are looking at the wet-plate collodion on glass photographic process. The invention of the collodion process is credited to Frederick Scott Archer in 1851-1852. By 1855 T. F. Hardwich had published his first edition of “A Manual of Photographic Chemistry, Including the Practice of the Collodion Process”, which was so popular there were five subsequent publications plus an American edition within the following four years.
Hardwich is listed on this title page as the “demonstrator of chemistry in King’s College, London”. The University of London was the first institution to offer photography courses, which were open to both men and women, albeit on alternating days, and Hardwich was their lead chemist. In the early 1850’s, just over a decade after the first official announcement of photography, the significance of this role would have put Hardwich among the top photo-chemists of the day.
His book, numbering nearly 400 pages, is a thorough outline of ‘The Science of Photography’, ‘Practical Details of the Collodion Process’ and ‘Outlines of General Chemistry’. For the purposes of this blog we mostly used Section II: Practical Details of the Collodion Process, which describes materials, techniques and chemical formulae variants.
We were assisted with this week’s entry by Richard Cynan Jones. Although well versed in several 19th century processes, he is predominantly a practicing collodion and calotype photographer from Wales. Richard actually has a modern reprint of Hardwich’s book and refers to it regularly when working with the process.
To clean the plate without scratching the glass, Hardwich first suggests caustic potash, however this is highly corrosive and some modern day practitioners use the more widely available “washing soda” or sodium carbonate mixed with water (which is slightly less corrosive). We actually used simple Calcium Carbonate (chalk) mixed with water and alcohol, which has the same result. This cleaning process ensures that there are no oils or residue left on the plate which would interfere with the collodion adhering to the glass. We did this the night before and wrapped all the clean glass plates in paper, as it takes a good amount of time, lots of light and a keen eye. We knew that our shooting would be outdoors and not ideal conditions for getting our glass plates perfectly clean.
The next day, we could simply un-wrap the cleaned plates and continue with the next steps of the process. It is recommended that you hold your glass plate at one corner or with a ‘pneumatic holder’ (a suction cup, as we did), pour the collodion into the centre of the plate, work your way around the four corners, as illustrated on page 226.
The excess collodion is poured off the final corner into a bottle, this part cannot be rushed or you could get lines of collodion across your plate. Once all the excess collodion has been poured off it will then go into a bath of silver nitrate where the chemical components will react and result in a glass plate that is sensitive to light.
Hardwich poetically states; “This part of the process, with which follows, must be conducted in a room from which chemical rays of light are excluded. It is inferred therefore that the operator has provided himself with an apartment of that kind” – or what we would simply call a darkroom. Richard regularly shoots outdoors and has a portable darkroom – also common for avid photographers of the day.
In the darkroom the coated plate is immersed in a bath of silver nitrate where the salts from the collodion mixture can combine with the silver resulting in a light-sensitive surface. Once the plate has sat in the bath for the appropriate amount of time – only determined by visual inspection where “the oily streaks upon the surface disappear, and the liquid flows off in a uniform sheet…” the sensitive plate can then be placed into the plate holder and taken out into the sunlight again without fear of exposure.
Techniques and tips for getting a well-made portrait, both in composition and exposure are briefly mentioned in Hardwich’s book, but he leaves much of this to the experience of the photographer. Test plates to judge light levels and timing are typically done to gauge the precise exposure times.
Once the plate has been exposed, the plate holder went back into the dark room to be developed.
Hardwich gives three options ‘according to the taste of the operator’ – which we were hoping was not a literal test of the formulae. On a developed plate the darker areas on a developed plate will have a bluey-green colour. The fixing bath will wash away this colour leaving the highlights a creamed coffee colour and shadows clear. The resulting image then appears in ‘negative’ form, so printing a positive will reverse this effect. The chemical formula given below notes the use of either Cyanide of Potassium or Hyposulphate of Soda (also called ‘hypo’ or sodium thiosulphate), both are commonly used by historic process photographers today. Given the dangers associated with cyanide, many opt for ‘hypo’, as we did, especially for public demonstrations of the process.
There are slight variations both in timing and chemical solutions for creating wet-plate negatives for printing, versus positive plates for ambrotypes. Each section of Hardwich’s book breaks down these variations for the reader. Although it was our intention to make negatives, we spent a good deal of time playing around with the chemical variations and ended up making ‘weak negatives’ which actually work rather well as ambrotype plates when backed with a dark card, which is what we did for these finished plates.
We did end up making one albumen print to illustrate this method so we could show off a final printed product. Freshly made albumen prints often did have a deep purple-brown colour to them, most of which is washed out during the fixing process. Most albumen prints that survive today have taken on a more yellow tone due to deterioration.
This video of Luther Gerlach who works with large format collodion, does a wonderful job of showing all the steps in the tintype process. A tintype is essentially the same as what is outlined in Hardwich’s book, however instead of glass, a piece of lacquered metal, ‘Tin’ acted as the substrate. Tin was never actually used in tintypes but the term was historically used to describe a “cheap metal”, commonly iron in the mid-19th century, but aluminium is widely used today.
— Rachel Nordstrom
Photographic Research and Preservation Officer
We hope that this blog has inspired you to explore the world of historic photographic processes. However, if you are attempting to use any of these methods and techniques at home, please do more research, refer to MSDS sheets for all chemicals and always use proper safety equipment. Many of the listed chemicals are highly corrosive or lethal (see first ingredient of ‘The Fixing Liquid’ for just one such example).
Note of Thanks
I would like to extend a huge thank you to Richard Cynan Jones, who came all the way from Wales to St Andrews to share his expertise with us and spread the joy of Collodion with the department (and readers).
Candid images by Rachel Nordstrom and Marc Boulay.
Collodion portraits by Richard Cynan Jones.