Glass plate negatives are one of the more fragile records we have in the archives. Those who remember the days before smart phones and digital cameras will be familiar with waiting for rolls of negative film to be developed into prints.
Glass plate photography was invented in the 1850s and was common until the 1920s. The technology for developing photographs has evolved over the century, but the basic process is similar. An image is created by exposing light to a photosensitive emulsion that is coated on a glass plate. Positive images are then made by placing sensitized paper in direct contact with the negative plate.
If processed correctly, glass plates can have a very sharp, clear image. Despite being 100 years old, the resolution is even much higher than many modern digital cameras, which can produce pixelated images.
The glass plate seen here (above, left) is in great condition. It shows some of the workmen who built Christ Church Cathedral. Architect J.C.M. Keith is identified in front row centre, sixth from the left. Using modern technology, I can digitally invert the photograph to show the positive image (above, right).
