Watkins Factor: developing

Posted on Posted in coursenotes, exs notebook, labnotes

Time of first appearance as estimator of developing time for that emulsion in that developer.

In re-working information about Deep/Thick vs Thin emulsions… da-net posers made me do it.

Deeper dive into Time-Temperature of photography.

  • Watkins
  • Sheppard and Meyer
  • Clerc, section 400, the influence of temperature
  • Clerc, section 380 & 381, watkins factors, & combined factors

How Does It Work?

Developing is a process of saturating the emulsion; surrounding the exposed material with fresh developer, then moving exhausted developer. This main process is agitation. The key part of the emulsion is the gelatin. Think of the emulsion as having depth, as well as surface. This emulsion, whether film or paper, has to absorb the fresh developer– this takes time. An induction time. How fast the exposed silver begins developing depends upon the strength (developing power) of the developer. It is affected by temperature, emulsion, etc, but the main factor was the developing agent(s) used.

The watkins method is mainly of use with emulsions suited to development by inspection. It is of great use in making lith negatives, or, somewhat, in making lith-prints. Sadly, in a developer containing two developing agents, the temperature coefficient loses significance when temperature varies much from 20 C.

Developing AgentC
Metol1.25
Paraminophenol1.5
Ferrous oxalate1.7
Pyrogallol1.9
Metol-hydorquinone1.9
Hydroquinone2.2 to 2.8
Catechol2.8

Some developing agents change activity with temperature — hydroquinone loses activity at low temperature. (Jacobsen, p.67)

Temperature coefficients vary slightly with emulsions. Concentration of developer has little effect.

The temperature coefficient of a developer is the increase in speed of development for a 10F increase. A TC of 2 means that a developer works twice as quickly at 75F as it does at 65F — typical Coefficients from the mid-century were: 1.8 for MQ developer(D76), for fine-grain developers (D23), and 2.3 for super-fine grain developer.

Note: pyro and amidol do vary by amount of grains per ounce. Bromide alters the pyro factor.

Compensating Timers

Temperature control is better than a compensating timer. Keeping agitation in line, changes of developer is more important to critical processing than is time-temperature duration. Build tray rockers, insulated, water-jacket trays with lids instead.

But, if you are interested search: Tundra. DLG. ProcessMaster.

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CARP Fishing

Posted on Posted in A Symbol Life, bead game, Carp Fishing, olden modern, The Biz

Writing about drying prints reminded me about Pakosol and drum drying of prints, even dye transfer prints.

Even though Kodak Dye Transfer paper was much thicker than most darkroom paper, it would still curl. This curl meant that retouching was harder, since retouching was the most common purpose behind making a dye transfer, we were making the process longer, and more expensive using any but the most efficient drying method.

I have, over many years, grown to test someone’s knowledge, trying to compare what they know by practice to what they know through overhearing; their gossip BS quotient. I did this because I hired people for labwork; since I didn’t have the patience to give them trial time, I talked, a bit, like an idiot, or I questioned them like their life depended upon correct, quick answers. In a way, it did.

A comment made to a Dye Transfer Group was that we used Pakosol when glossing our dyes. Not exactly true, although it went unchallenged. People too polite, or just didn’t have enough experience, which they realized. Only one of the 100+ talkers had lab experience; he was at BK+L. He may have known the use was to wipe the borders, not immerse the print for glossing, since those of us making dyes commercially were sending them to retouchers.

Wiping to White — clearing the borders was common practice; it carried over to “flashing white” to type Rs & Cibas. Art Directors expected R(review) prints to have borders they could write/markup.

Dye transfer died because of bullshit trumping behavior. As in most idler things, most people just doodle away, preferring to talk about it; so too in the camera counter world. People learn by shopping means they learn little of use beyond the sales chatter. The gossip review. The Efke Orthomatrix sold less than a third of what was made. No one bought more than 10 boxes! US importers basically stiffed the exporter.

Amateurs want a claim to meaning. This explains, rather, it justifies the costs of an in-effective hobby.

Back to print flattening: the solution is hygroscopic — something like dilute glycerin. Pakosol had glycol in it.

kodak’s 50s advice about drying paper flat.

dampen backs and re-dry between blotters under pressure.

Print flattening solution works well by slowing drying in winter atmospheres

[ from yesterday: https://webionaire.com/2023/04/02/drying-fiber-prints/ ]