Lecture Notes on Early Photography Techniques

Introduction

• Discussion on the Gat types and early photography processes.

Gat Types (Direct Positive Photographs)

• Made on sheets of copper, silverplated.
• Unique photographs, not printed on paper.

Preparation of the Plate

1. Cleaning the Plate

   • Ensure the plate is clean, free of dust and grease, and polished.
   • Used buffing boards for polishing.

2. Making the Plate Light Sensitive

   • Utilization of a sensitizing box.
   • Two ceramic dishes: one for iodide solution, one for polished plate.
   • Iodine vapors react with silver to create silver iodide (light sensitive).
   • Exposure time: 15-20 minutes.

Making the Exposure

• Place sensitized plate in a plate holder in the camera.
• Remove lens cap for exposure; no visible image is seen immediately (latent image).

Developing the Image

• Chemical Treatment
  • Use of mercury for developing the image.
  • Exposed plate placed face down in a developing box over a tray of mercury.
  • Heat from a spirit lamp vaporizes mercury, reacting with silver to form a visible image.

Fixing the Plate

• Use of sodium thiosulfate (hypo) solution:
  • Place plate in solution to wash away unexposed silver iodide.
  • Agitate the solution to ensure thorough fixing and prevent further darkening.

Gilding the Image

• Final stage before protection:
  • Use a gilding stand with gold chloride solution.
  • Warm the plate and pour the solution, enhancing and protecting the image.
  • Final washing with distilled water before placing in a protective case.

Limitations of Gat Types

• Major drawback: Direct one-off positives.
• Multiple copies required rephotographing the subject or the original deger type.

Tolbert's Process: Negative Positive System

• Introduction of the negative-positive process by Tolbert.
• One negative can produce multiple positive copies.
• By early 1860s, the use of deger types had significantly declined; the future of photography lay in negative-positive processes.