Getting The Picture – Understanding the Basics of Glass Plate Negative Photography

Here at the Past on Glass project we’ve become accustomed to handling glass plate negatives and being enthralled by the images we’ve retrieved from them, but we sometimes wish we could visit the Knights-Whittome Studio and see for ourselves how it was done.

A few tantalising images give us some small clues about the studio set up, but unlike some other digitisation projects such as that of the Reeves or Winter’s collections of Lewes and Derby respectively, Knights-Whittome’s original studio, records and even equipment are all long gone.

Knights-Whittome at the investiture of the Prince of Wales, the future Edward VIII. This is one of the only images we have of the photographer with his camera.


A selection of plates which offer a small glimpse of the studio set-up

Alongside the rehousing and scanning of the plates themselves we have also been cataloguing the information written on the original envelopes which housed the plates. 

As well as an (usually!) unique identifying number, the envelopes offer details of the surname of the sitter or subject, sometimes an initial and/or title, plus a date. There is also usually a brief, often abbreviated summary of the orders placed against the plate. This summary rarely contains additional information pertaining to the client, nor does it usually give a price. We know from correspondence that a ledger or order book was lost at some point, so can assume that this information would have been stored separately.

Sometimes the instructions are lengthy, with detailed retouching notes, and dates for completion. Others are very brief: ‘6 Bromide’. As we have worked our way through, we have compiled a glossary of commonly used abbreviations and terminology. Again, some are very clear and can be understood easily, others seem baffling. The ongoing battle to decipher handwriting and understand these instructions has inspired us to find out more about what these instructions might have meant. The envelopes are in a dirty, fragile condition but they’ve yielded some precious information about the techniques which were used.

Kathy Nichols, a valued volunteer has put together this guide to the process of glass plate photography which explains some of the abbreviations that we regularly uncover.

Using Glass Plates to Take a Photograph

Photographic glass plates preceded photographic film as a capture medium in photography. A light-sensitive emulsion of silver salts was coated on a glass plate, which was then exposed to light, capturing the image. Originally plates would have been ‘wet-coated’ at the time of use, and pages from Knights-Whittome’s early notebooks devote many pages to this process and the ‘recipes’ required. However by the late 19th century pre-coated gelatin dry plates were largely in use.  They were the first photographic negative material that was manufactured and mass produced.  Among the few artefacts we have in the collection, and saved largely because they were re-purposed to house loose plates are some of the original manufacturer boxes in which Knights-Whittome would have purchased his plates.  These offer instructions as to developing the plates.

Ilford Plate Box

Once satisfied that his subject was sufficiently well lit and positioned in a visually pleasing way, the photographer would select a dry plate and take the following steps. (The dry plate or gelatin silver glass plate negative was manufactured using a sheet of glass coated with silver based light sensitive materials suspended in a gelatin solution which had been bonded to the glass using heat.)

  1. Place a dry plate contained in a plate holder into a slot in the camera.
  2. Slide the cover from the plate holder to uncover the dry plate.
  3. Uncover and then recover the lens. By 1880 photographic plates were so sensitive that an exposure of less than a second was often enough to achieve the desired result.
  4. Slide the cover on the plate holder back over the dry plate.
  5. Remove the plate holder containing the exposed plate which was now ready for processing in a dark room.

Developing and Fixing the Negative

  1. Moisten the plate with distilled water.
  2. Place in a glass or gutta percha developing dish and cover with developing fluid.
  3. Wash thoroughly when image  has appeared
  4. Place in a bath of fixing solution and then wash and dry the plate. It could also be varnished at this point but this was rare after about 1890.

Printing the Photograph

The printing process chosen would depend on the type of result desired.  Here are some that are mentioned on the Knights-Whittome glass plate envelopes:

Printing Out Paper Process (frequently abbrieviated to POP)

Printing Out Paper was a fairly thin paper treated with photosensitive silver chloride crystals in a gelatin glaze. It was used for printing photos which were to be mounted on strong card such as cartes de visite or cabinet prints.  These prints would usually be toned and fixed but proof prints could also be made (used to judge how good the negative was) without using toner and fixing solution. We sometimes find proof prints in the envelopes containing the glass plates but the images are usually much degraded.

With the Printing Out Paper process the image was developed solely though the effect of light and didn’t require further development with chemicals.

  1. The POP paper would be placed under the negative in a special frame
  2. it would be exposed to daylight or artificial light until the image developed
  3. The print would be washed in water to remove excess chemicals
  4. then toned using gold and platinum toners (to convert the silver into more stable compounds)
  5. washed again and fixed using standard fixing solution
  6. air dried or squeegeed on a clean polished glass surface and allowed to dry

Platinum Print (often abbreviated to Plat)

The platinum print (also known as the platinotype) was often used for landscape or architectural photographs.

In this method the metal deposited on the paper through a series of chemical reactions is not silver but platinum.

Paper treated with a mixture of iron salts and a platinum compound would be exposed to light in the usual way and the image would then be developed out using a solution of potassium oxylate.

The platinum print had a great range of subtle tonal variations, usually silvery grey and was valued for its permanence. Unfortunately the price of platinum went up enormously and by 1907 was 52 times more expensive than silver. Most production of platinum paper stopped by 1916 though platinum prints are still produced by artists and enthusiasts.

Carbon Print

In the carbon printing process the paper used is made with carbon pigment treated with light sensitive chemicals suspended in a gelatin emulsion.  The paper is exposed to light through the negative and this causes the gelatin to harden more in the darkened areas than the lighter ones. The print is developed by washing it in warm water so that the softer gelatin comes away and the darker areas remain.

It has a matt finish and can be produced in a variety of colours ranging from rich sepia tones to cooler shades of blue and grey. Carbon prints are resistant to fading and so were often used for commercial editions of photographs.

The technique was difficult and time consuming but highly regarded amongst photographers.

Bromide Print (abbreviated as brom.)

Bromide prints were the standard type of black and white photograph in the twentieth century. The light sensitive emulsion on the photographic paper was made with silver bromide and produced neutral black or cold blue-black tones.

Other Terms Found on the Envelopes:

Bristol board – A type of stiff extra smooth card used for mounting photographs or for drawing and sketching.  It is normally white but comes in other colours

Cabinet print – A cabinet print was a format first introduced in 1866 as an alternative to the carte de visite (see below). It was a paper print mounted on stiff card roughly the size of a postcard. There would be side borders of perhaps a quarter of an inch and one inch at the bottom.

Knights-Whittome’s instructions for cabinet print orders include “on Burlington”, “on Riviera”. These were probably mounting cards with a particular design on the back which would have included the photographer’s details. Other orders specify colours such as green, grey or sepia.

Cameo – Portrait in an oval format

Carte de visite (often abbreviated to CDV) – a format for photos which was extremely popular with Victorians during the 1860s and continued to be fairly popular until the 1890s. It became little used after the advent of the postcard format around the time of the First World War.

A carte de visite was a paper print roughly the size of a playing card which was mounted on some stiff card of the same dimensions as the photo but with a half inch border at the bottom. The name of the photographic studio would usually be printed in this border area and more details would be on the back. We don’t know what the Knights-Whittome mounts looked like and would be interested to hear from anyone who has an example.

Mezzo  – Probably refers to Mezzo Tone photographic paper, a silver gelatin self-toning paper produced by Eastman Kodak. It was used to produce a warm toned sepia coloured print.

Vignette or Vig. – When a photograph is vignetted the image is faded towards the edges.

There are an array of other abbreviations and terms for which we cannot find adequate reference.  ‘Sepoy’ appears regularly, ‘Sutton or Woodcote Ovals’, Ivorine, Seltone, Riviera, Cosway, Lewis, Watman – all presumably styles of mounts or papers that Knights-Whittome offered his clients.  Other abbreviations which stumped us for a while seem obvious once they have been deciphered ‘Chr. Cir’ for example is ‘Christmas Circles’: ‘RO’, ‘right one’ in reference to the printing of doubly exposed plates.  No doubt there are some terms we will never understand – such is the esoteric nature of the annotation on these envelopes-but they continue to spark regular debate and conversation in the Past on Glass studio, which is just part of the fun of the job!



The National Media Museum

Stulik, Dusan, and Art Kaplan. 2013. The Atlas of Analytical Signatures of Photographic Processes. Los Angeles, CA: Getty Conservation Institute.
The Victorians in Camera by Robert Pols, published by Pen & Sword (2015)






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