52 Weeks of Historical How-To’s, Week 50: How to Varnish a Collodion Plate
Back in Week 15 of our Historical How-To’s, we created some collodion wet plate negatives. It is here that I must confess we did not actually finish the job. Any collodion photographer of the Victorian or modern age would tell you that if you want to keep your image you must varnish it. This is where we possibly failed our readers (or left ourselves open for a follow up blog perhaps?). Collodion images are notoriously fragile, prone to scratches and tarnishing.
Special Collections has recently acquired about 250 early collodion negatives, dating to about the mid 1850’s, taken at the home of Lord and Lady Kinnaird at Rossie Priory in Perthshire. The Kinnairds were early champions of photography and, besides practising photography themselves, they encouraged the development of the early processes here in St Andrews with the help of Sir David Brewster, Dr John Adamson, Hill and Adamson and Thomas Rodger.
Some of these images came to us unvarnished or partially varnished. As the process of varnishing a plate takes almost as much time as making the image itself, plates were probably not varnished unless they were likely to be used for printing. At first glance, many of the Rossie Priory images appear to be stereoviews, however upon closer examination about a third of them are actually pairs of images, most likely taken with a stereo camera but making two separate exposures of slightly different poses. In most of these cases only the better pose was varnished and the less-flattering pose left to the elements.
So promptly we decided to varnish our plates to ensure their long-term survival.
The varnish is a mixture of crushed up gum sandarac mixed with alcohol, and some lavender oil added to ensure it doesn’t dry too brittle or hard.
To make sure the varnish will spread evenly across the plate both the varnish and plate have to be warmed to similar temperatures. The vial of varnish can simply be placed in a mug of hot water, but the plate has to be slowly and evenly heated over an open flame – being sure the image side faces up so as to not burn off the image. Once they are both warm, the varnish is poured into the middle of the plate.
Allow the varnish to slowly fill the plate, you don’t want to force it too quickly to the edges or the varnish will pour off the sides, and likely all over your hands. The varnish and plate immediately begin cooling down, so the varnish flows much more slowly, and as the alcohol evaporates the varnish hardens. It has to be spread quickly but not in haste – a fine balance!
When the plate is nicely covered the excess varnish is poured off. The varnish is very sticky and messy so to keep it off our hands great care has to be taken, gently tilting the plate while balancing it on fingertips from beneath. Once the varnish stops dripping, you can dab off the edge and hold the plate by the corners.
The varnished plate now has to be dried. This can be a bit stressful as you are again warming your precious collodion image over an open flame, but this time your plate is also surrounded by vapours of alcohol. If you watch the flame closely you can see it wicking up to the plate following the trails of alcohol.
First time varnishers sometimes panic a bit when they see their image fog up as it dries, but this is simply moisture condensing as the alcohol evaporates. If you do not continue to dry the plate thoroughly through this phase of the process it can result in a mottled and pockmarked varnish layer. Drying the plate evenly and letting the all the fog dissipate will give you a beautifully glossy image surface.
It is important to remember that the surface is still sticky and shouldn’t be touched or rested up against anything for at least a day.
Happily, all our plates were varnished without incident, and my flat had a lovely smell of lavender for days afterwards.
Rachel Nordstrom and Eddie Martin
Note: All reference numbers in this blog are temporary photographic numbers [PHtempxxx] as they are still in the process of being digitised, rehoused and catalogued. Keep an eye on the blog or our photographic collection database for information when they will all be available online.
Special thanks to the Roger Watson at the Fox Talbot Museum for a loan of the varnishing materials and supplies from the workshop stores.