Category: collotype

friday: Collected Maybe

Posted on Posted in alt photo, collotype, labnotes

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.

Separations: start here

Posted on Posted in collotype, coursenotes, dye transfer, exs notebook, labnotes

notations on making separation negatives. bits from the past intended for today.

DSChromeCN
R252970
G586199
B4747b98
wratten filter numbers

direct seps are easiest, but you create “time seps” as well — trichromie. 

contact seps are easier than enlarged seps. 
learn what standard light is -- then you can begin to translate "old" literature. Use the theory and experience of those who made their living in labs.

contact: standard light
 standard light - tungsten -
first, early innovator lab: Evans & Peterson Color 
K&M filtermatic and K&M Point Light … Omega ULE system
3 FC = .3 density from a 3.0 wedge density
AIM ~= .4 shadow negative

using silver density steps will introduce you to the “green problem” — aka, green gaps
calibrate with color strips &&& silver wedges

derive “Relative Exposures” of the sep set
29, 61, 47b

notes from tabula rosa: super XX to Tmax. XX is twice over. convert those historical refs to current start points. Oh. use HC-110 B at 72F
—
visual evaluation/ no densitometer, make a BW print onto known paper.
print the Green Sep, unless GREEN is the dominant scene color. (then use red)

—
First seps from: DuPont Fine Grain Pan (20x) easy

Grain of seps: 1975-80)
Plus-X -- lowest, best enlargement
Sep Type 1 (reciprocity notes)
XX - highest grain
         -Green: less exposure longer Development
—
DS Base exposure: (working with ‘factors’)
(25) Red ~=~ 1
(58) Green +1/3
(47) Blue + 2 2/3
OR take blue as the base exposure, then apply ND filters to the RED & GREEN exposures.

— newton ring 
offset powder // gum glass
watch RH of film room.
don't mix exposure, storage, processing stages in same room.
—
tmax contact [at asa 6]
29	24 sec
61	14 sec
47b	135 sec

—
HC 110 A,B  // C,F
DK50  st, 1+1 // 1+2, 1+3
D76	st, 1+1 // 1+3
Seps // masks
from back in the day:
Dupont 16D  6,7,8,9  == for gammas of .6 to .9 /.Sure made it easy.
--
watch how you dry the seps. angles matter. never force dry (use "secret" dryer)
learn how to mix D76 so it doesn't "shift" on you. Oh, avoid those who don't know how.

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two shoes

  • the path is the destination
  • the destination isn’t on any path
  • MA (japanese)

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PS. what do I currently use? Ilford: delta, ortho plus, fp4+ — not Kodak. I have it. Have used it. don’t now.