The appeal to photographers of the silver gelatin dry plate process was that once prepared, plates could be stored in the dark until needed. Once exposed, the plates could be stored again until it was convenient to develop them. Introduced in the 1880s, the use by photographers of gelatin dry plates lasted for over a century until commercial production of the plates ceased in the 1990s.
Prior to dry plates, photographic images were created using collodion wet plate processes. Collodion is a clear, syrupy solution of cellulose nitrate in ether and alcohol. When poured onto a suitable substrate such as tin or glass and then sensitised with iodised silver nitrate solution it becomes sensitive to light such that it can be exposed in a camera to record a latent image. The image is subsequently developed, fixed and once dry, is protected with a coat of varnish. The process from pouring to fixing needs to be accomplished in the ten to fifteen minutes that the sensitised collodion remains ‘wet’ and so the photographer has to have his or her whole processing paraphernalia to hand when the exposure is made.
For the past couple of months I’ve been experimenting with gelatin dry plates and still have much to learn. However an Ambrotypes Workshop at the St Andrews Photography Festival led by Brittonie Fletcher caught my eye. It interested me enough to book my place and take that step back in time to learn more of the earlier process. Ambrotypes are a variant of the wet plate collodion process, producing a positive image on glass which is viewed by reflected light when held against a black background.
And so it was that I met with my classmates for the day, Paul and Fiona, together with Brittonie and her assistant Pippa. The venue was a pop-up tent darkroom on the library lawn of St Andrews University. After a little talk on the place of ambrotypes in the history of photography and what we would be doing, Brittonie set us on the task of preparing our glass plates before introducing us to the cameras and to the contents of the darkroom.
Preparation involved thorough cleaning of our plates with whitening (calcium carbonate) mixed with a little spirit. The residue was rinsed off with distilled water and left to air dry. Once dry the edges of the plates were given a light coating of albumen (egg white) to help the collodion grip the plate. While we waited for the plates to dry we checked the function and cleanliness of the plate holders into which the plates are loaded to make exposures in the camera, and prepared the developer, stop and fix chemistry for the darkroom.
Within the darkroom was a trestle table set out to follow the process we would be using: pour the collodion, sensitise the plate, clean the back of the sensitised plate and load it into a plate holder. At this stage the holder is taken to the camera, exposed and then returned to the darkroom. Back in the darkroom, remove the plate from the holder, pour developer over it while held and gently agitated above a tray for 12-15 seconds, move to the next tray to stop the development by pouring distilled water over it, place in the tray of fixer and leave there until the image clears. The plates now need to be thoroughly washed to remove all excess chemistry and two more trays filled with distilled water are used for this. Finally, leave the plates in a rack to air dry.
Except for the stages of pouring the collodion and sensitising the plate, the process is essentially the same as is used in most developing processes. I have some experience of developing film, paper and glass plates so it was with the collodion-specific stage that my main interest in the workshop lay.
The technique required to pour collodion is similar to that of pouring gelatin emulsion and so I already had a feel for what to do. However I found collodion to be more fluid than emulsion and it was easier to ensure corner to corner coverage of the plate before pouring off the excess. The smell of ether was quite evident even though our darkroom tent was well ventilated. There was little doubt as to the risks faced by nineteenth century photographers in their quest for images while working with a potentially explosive material in an anaesthetic atmosphere!
Over the course of a most enjoyable and informative day we produced at least three plates each and I think we achieved a 100% success rate with no failures and well exposed plates all round. My three plates were left drying and I will get them in due course from Brittonie, to finish off with a coat of protective varnish.
Ambrotypes are intended to be viewed against a dark background, whether by painting the back of the plate or by mounting the plate in a frame on backing material such as black velvet. I’ll have to wait and see how well they will scan so that I can post them here or in a separate post.
I just couldn’t resist turning up for a photographic occasion without a pinhole camera! The header image for this post is a pinhole image of the darkroom tent in situ, exposed on glass coated with SE1 emulsion and loaded in a homemade foamcore pincam. It is not an ambrotype image!