Originally Posted by Photo Engineer
I like this, photographic forensics!
I've just bought a pack of vintage glass plates on eBay. They were made by the Brittania works, later to become Ilford limited, so must be from the 1890s.
I bought them for historical interest only, the unused plates have been exposed to light years ago and are of no value, well so I thought so until now. Maybe they hold some secrets about 1890s production techniques!
After close inspection I can see that there is overspill along one edge, but the other edges are clean. Also there are streaks on the back - and an emulsion finger print!
I conclude, Watson, that the plates were hand coated as a whole plate and some of the emulsion must have run across the back during coating and stuck to the rear of the plate, where the maker dabbed his finger in it . The plates were later cut into quarter plate sizes with a glass cutter, leaving three clean edges and one covered in emulsion run off.
I've tried a few photos, although they are not easy to photograph, being very reflective. The first pic is the back of the plate. To the left of the vertical streak is the fingerprint, but on the actual plate these marks appear silvery, rather than brown. The other two pics show the edges, mucky edge on the left, clean on the right. Note the chips where the glass has been cut. These chips do not contain emulsion, except on the 'mucky' edge.
These plates must have been very silver rich. It looks like the silver salts have reverted back to the metal: is this possible? They are very shiny in places.
Last edited by steven_e007; 07-13-2007 at 07:18 AM. Click to view previous post history.