friday: Collected Maybe

many small readings. short hand notes.

st/ages of theory: how-to / what / why

learning from the hobby lobby means you may never know a reason. you probably won’t ask them questions, after-all, you and they are just hanging onto each other’s opinion. You will never ask where he saw that work. Unless you remember, because you were a member of the academy, you wouldn’t realize that geography was a strong barrier to exhibitions in the 70s and 80s.

Dichromated Gelatin

ask the other camps. look in books and journals. maybe google has a bigger, better memory than you realize.

The advantages of Dichromated Gelatin over Silver Halides are:

  • More efficient recording material.
  • Has less scattering.
  • Is more transparent.

as dichromate is exposed absorption spectra changes.

the broader the exposure spectrum, the deeper the hardening reaction.

characteristics are listed below.

  • Initial thickness of the gelatin layer
  • Initial hardness of the gelatin
  • Concentration of sensitizing dichromate bath
  • Drying conditions: temperature, humidity, and time
  • Exposure, wavelength and energy
  • Time delay between exposure and processing
  • Alkalinity and temperature of processing baths
  • Composition of processing baths
  • Time in processing baths
  • Recording geometry

Factors Influencing Light Geometry

(a) Size of the light source. The larger a source, the greater becomes the angle of light rays travelling from its edges and therefore the degree of undercutting.

(b) Position of the light source. The nearer a light source is to the vacuum frame the greater is its effective size. Conversely if the lamp is moved further away, so its effective size is reduced. It is good practice to increase lamp distance when exposing very fine detail work to reduce the effect of light undercutting if at all practical, (do not forget that the exposure time will have to be adjusted if an integrator is not fitted).

the “printing out” tanning is similar in contrast effect as the “developing out” of tanning developers. DAS / Dichromate systems share the exposure effect: judge by depth of “cure” — tanning, hardening of the colloid. DAS exposure should begin with 365nm wavelength.

Absorbance and sensitivity are different. This is partial explanation for why color of exposing light should be broader with a longer (more depth) exposure requirement.