Monday, 22 August 2011

Dry Glass Plate



A short history
At the turn of the 20th century the dry glass plate replaced the commercially used wet plate collidion process. Dry plate was much easier to coat and process but it's main advantage was that the plate could be pre coated days, weeks even months before exposing and developing. This advantage left the wet plate process obsolete because of its need to be coated, exposed and developed-all within 15 minutes and its need for a portable darkroom. Later advances in dry plate technology meant that photographer no longer had to coat their own plates but they could buy readymade plates from manufactures such as Ilford and Kodak. Commercial photographer’s love affair with the dry glass was short lived and was quickly replaced by black and white film. Film managed to correct two main problems with dry glass plates: film had a large tonal range, therefore landscape photographers were now able to capture clouds in their images, which was unable to be achieved in both wet and dry processes; the other advantage to film was it didn’t smash when it was dropped but was very light and flexible compared to what photographers were used to.          




Ingredients

-Silver gelatin emulsion (liquid light VC)
-Normal silver gelatin paper Developer
-Normal silver gelatin paper stop bath
-Normal silver gelatin paper fixer
-Polyurethane varnish
Equipment
-Paper towel
-Gloves 
-Dishwashing liquid
- Wash trays x4
- Beaker
- Glass (we are using 3mm frames glass, cut to size)
- 4x5 film holders (modified to hold glass plates) Or original glass plate holders (if you come across any)
- Camera- 4x5 (you can also use any box brownie/drop plate camera, simply cut the glass plates to suit the camera size)
-Tripod & cable release


THE PROCESS:
NOTE: The process achieves its best results when the temperature is under 20c as when it is damp or hot the emulsion may have trouble sticking to the plate and warp or buckle.
Subbing

The layer needed to bond the emulsion to the glass

Traditional Subbing
Can still be used today

-Gelatin
-Chrome alum
-Distilled water
-Photo flo
Step 1: Warm 50ml of distilled water to around 50c, then add 1g chrome alum (hardening agent) and mix until dissolved.
Step 2: Sprinkle 3.5g of gelatin into 236ml of distilled water, and then let it sit for 15mins while the gelatin swells. Now warm the mixture to 50c and stir until the gelatin has dissolved.
Step 3: Now add step 1 to step 2 and mix through.
Step 4: Add 15ml of photo flo to the mixture. Keep the mixture warm and coat the (Chemical Clean) glass with the subbing. Allow to the plate to dry for 8 or more hours
Contemporary Subbing –What we are using today

In this workshop we are using Polyurethane varnish
Step 1: (Chemical Clean) the pre-cut glass plate. First wash in hot soapy water using a brush, then wash in just hot water until there is no soap left on the glass. Rinse with distilled water this stops water mark. Then dry the plate.
Step 2: Polish the plate to remove any water marks
Step 3: Warm the polyurethane varnish in its container in a warm water bath (do this in ventilated room or outside)
Step 4: Pour the vanish onto the glass and then lay flat to dry.

Under RED light only

Step 5: Warm the silver gelatin emulsion in its container in a warm water bath ( do not warm in hot water it may damage the gelatin and the silver in the emulsion)
Step 6: Then apply the silver gelatin emulsion to the glass over the varnish
Step 7: Lay flat to dry in a completely dark place, the plate may take a couple of hours to completely dry (plate does not need to dry to be ready to use-it can be used straight away whilst it is still wet-but when shooting in the field make sure plates are completely dry before stacking them together for traveling).

The plate is now ready to use in camera


Expose plate

The exposure will depend on the emulsion used; I use Liquid Light VC which has an ASA/ISO of 2 and Ag Plus which has an ASA/ISO of 8. Double coat of the emulsion will half the exposure time and if you add extra silver nitrate to the emulsion will also speed up the exposure.
ASA/ISO= is the measure of the film's sensitivity to light. Low ISO/ASA is considered slow film as it is less sensitive to light-therefore takes longer to expose a picture onto the film.
Notes:If the plate is overexposed it will be too dark/if under exposed it will be too light.
-It is best to produce a plate that is slightly overexposed (rather than under) as to produce deep blacks-but it really comes down to the photographers personal tastes.
Under RED light only
Developing
(Best done at below 20c as the temperature could cause the image to lift or buckle)

Note: Develop like you would normal silver gelatin paper.
Bath 1: Developer (2mins)
Bath 2: Stop Bath (30sec)
Bath 3: Fixer (3-5mins)
Bath 4: Wash (10-30 mins)
Leave plate in a cool area to dry plate-never force dry the plate.
- You will now have a negative image that can be scanned, used in an enlarger or contact printed to produce a positive image.




Chemicals:
ACE Chemicals(SA)
www.acechem.com.au
Total Photographics (SA)
www.totalphoto.com.au
Gold streets studios (Vic)
goldstreetstudios.com.au
Bostick and Sullivens (USA)
bostick-sullivan.com
References:

The alternative photography website
alternativephotography.com
The book of alternative photographic processes
C, James, 2009, The book of alternative photographic process, Delmar, USA

1 comment:

  1. Great information, thank you, I will have a busy weekend!

    ReplyDelete