In this blog and the next entry, I’ll be going over how to handle, clean, store and digitize your glass plate negatives. Properly caring for these negatives is important to ensure that they continue to survive for decades (and centuries) to come, and so that the image emulsion is not inadvertently damaged by improper storage and handling. Please also consider cataloging your negatives as you go through this process. A related blog entry on cataloging can be found here.

If you’re starting an extensive archive of 19^th century archives that includes photographic material, you will likely eventually run into glass plate negatives. These are different from tintypes, ambrotypes and daguerreotypes. There are two types of glass negatives: wet collodion (used between 1855 and late 1880s) and gelatin dry (used from the late 1880s to the early 1920s). The main difference between the two is that the wet collodion glass plates would need to be prepared by the photographer and immediately exposed and then processed by the photographer, all while remaining wet. The invention of gelatin dry plate negatives allowed the photographer to prepare the glass plates in advance before exposing them to light. By the 1880s ready-made gelatin dry plates were available for purchase to photography studios and amateur photographers alike. By the 1920s these plates were being replaced by dry gelatin paper negatives and flexible celluloid film rolls.

How NOT to Store Glass Plate Negatives

In all honesty, coming across a batch of glass negatives in this situation is not the worst-case scenario. They are at least wrapped and somewhat protected from the environment and each other, which far beats them just scattered loose in a box without any protection. Still, this is not ideal.

How to Store Glass Plate Negatives Instead

Here you can see some glass negatives in protective sleeves inside an archival box specifically made to house them. These dividers accommodate 3-4 plates (depending on thickness) in each pocket. Now, special note here: I have these plates sitting vertically in this picture. This is because I am in the process of digitizing them and it allows me easier access to remove each plate. For proper long-term storage, these plates would be turned onto their long edge so that they would fit snugly between the dividers of the box.

There are a few archival businesses who sell specially made glass plate negative boxes and dividers. The one seen in the photographs here is from Talas and can be purchased here. You will need both the box and the folding protective sleeves.

Important things to Consider

• You will want to wear gloves when handling these negatives. You don’t want to run the risk of getting fingerprints on them or scratching the emulsion. However, cotton gloves can snag on the emulsion (especially if it is already flaking) and they also can make your grip slippery, and dropping a glass plate negative would be very BAD. Instead of cotton gloves, use latex or nitrile gloves that have a more rubbery texture.
• The emulsion side of the negative is EXTREMELY fragile. It can scratch off, be washed off, and even just flake off over time. Be extremely careful when handling and do not handle the negative where that can be damaged. Grip it from opposite edges, like you’d hold a CD, do not place your fingers on the emulsion.
• Your negative may discolor over time. This is natural and due to the chemicals involved. Wet collodion plate negatives tend to turn brown or have a sepia tone due to the varnish that was applied to them. Gelatin dry plate negatives were sometimes varnished and can have a purplish tone but usually have a grey or black image tone.

Cleaning Your Glass Plate Negative

Ideally, this is something that should be done by a professional, but I know there are some antiques dealers and collectors (I’m not pointing fingers…) who can be a little brazen with their attempts to “spruce up” their collectibles, and I’d rather provide solid information for those who are going to forge ahead anyway, instead of not including it.

This is important and also very risky, as you do not want to damage the negative in the process. Do not attempt to clean the emulsion side with any liquids, chemicals or solvents.

The West Virginia University Library outlines a good step-by-step process to clean the glass side (non-emulsion) side of a glass plate negative using ONLY distilled water. If you choose to do this, please follow their steps closely and carefully in order to avoid any unintentional damage.

As opposed to doing this yourself, you may find that your local museum or university archive may be able to help you—or may even help clean them for you. In the next post I’ll go over how to digitize your glass plate negatives and that is also something that your local museum or archive may also be able to assist with.

The most important thing to remember is to not do anything that is irreversible—in other words, don’t wash off the emulsion! And always remember to ask questions if you are unsure of what to do. There are resources available online and also locally at museums and archives who can help you.