Category: labnotes

What is “Old Brown”

Posted on Posted in labnotes, morning wood, the LabTagged , ,

from days of Harvey’s [CHQ] and Edwal developers. It is seasoned developer, developers before greater knowledge of buffering the emulsion byproducts of developing. Fresh developer (777) was mixed in clear glass bottles; into this was put the butts and tails of the roll of film. After enough time, this clear became cloudy. This aged film was put into “old brown” jugs. Old brown was used as starter for “clear”

in paper terms, it doesn’t mean exhausted hydroquinone, it means chemicals from the paper emulsion intermixing with developer chems. In early days, when lith was a commercial, highly controlled procedure for making controlled dots, this could be a ‘bang’ paper such as Broivira 6. Current use of “old brown” can mean the seasoned [weaker] developer used in solarization, more likely OB means seasoned LITH developer.

These high contrast papers had cadmium, and rhodium chloride essential for high-contrast long storage paper. a darkroom would have grade 5, or 6 in stock, but likely use infrequently. These paper found their way into splashboard processes such as solarization, and lith, with lith meaning using exhausted developer from the lithographic side of the shop. These prints took on coarse clumped particles of warmtone hues, unlike lith-proof paper which remained true bowntone when processed in lith developer.

Like many specialties, photography borrows terms from existing fields. We also adapt concepts: old brown is similar to Solera:
[ Solera is a process for aging liquids such as wine, beer, vinegar, by fractional blending in such a way that the finished product is a mixture of ages, with the average age gradually increasing as the process continues over many years. The purpose of this labor-intensive process is the maintenance of a reliable style and quality of the beverage over time.Solera means “on the ground” –wikipedia]

Techday: Oct 8

Posted on Posted in coursenotes, labnotes, the fora

tuesday notes in passing.

Emulsion Making

  • Laboratory-scale photographic emulsion technique
  • Thomas T. Hill. A Tutorial Paper: Photographic Gelatin and Synthetic Colloids for Emulsion Use. Journal of the SMPTE 1968, 77 (11) , 1185-1188. https://doi.org/10.5594/J10922

DARKROOM safety: If mixed use, meaning, your kitchen, bathroom etc serves as a chemical mixing, storeroom, darkroom — think it is riskier if you share it with others, cats, children… Consider this: powder can collect: cabinets, containers, exhaust ducts, sink drains. Kodak’s dye transfer process relied on Pyro as tanning developer. One lab (MPC in Texas) was referenced by Kodak technicians for years to Portrait / Wedding photographers. The facility was declared hazardous waste site because of the contamination in the pipes and vents.

You aren’t going to be sloppy, but what do you expect to gain by mixing from “skratch” — if you expect that there is a secret to your trial and error chemistry, be prepared to accept more consequence. While it is true that food is a complex of chemicals, which taken in isolation seem dangerous. That is also true of the earth we walk. I am not prepared to call it poisonous, nor hazardous. I am not careful about eating apples, nor am I carefree in mixing raw photochemicals.

I mix chemicals, and have since 1960. In that time, I have increased my skill and cuations considerably. When mixing tanning developers, i use a glove box. My sink has multiple levels of exhaust — for heavier than air, and for lighter, the airborne items. My drains are changed, with the pipes turned in at hazard sites. My exhaust vents are also “smooth” channel with drop caps for cleaning.

Reminder: flakes “flake” into dust; dust into finer powder.

Is there a disadvantage, do you increase risk if you wear PPE? What do you give up, lose, surrender? What are the motives of those on the hobby boards? Is their situation the same as yours? Do you think they would assume your losses if you have an accident?

WHAT DO YOU do for a splash to the eyes? If it is apple juice?


Acute Oral LD50 is the dose of a substance or mixture of substances, in milligrams per kilogram of test animal body weight, which, when administered orally as a single dose, produces death within 14 days in half of a group of 10 or more laboratory white rats.
The oral LD50 of arsenic ranges from 15 to 293 mg/kg in rats, and from 11 to 150 mg/kg in other experimental animals

——-

TANNING effect — if current products exhibited differential tanning, dye transfer [imbibition printing] wouldn’t require special emulsion making. Using Kodak’s Tanning developer shows no sogn of tanning Tmax, Delta, nor FP4 films. Although silver is developed, and leaves a ‘hole’ in the colloid if it is bleached out, this isn’t tanning — D23 produces the same effect.