Dry plate emulsion drying time

Nodda Duma · Jan 3, 2016

Just curious... After you've poured your emulsion and set the plates in a light-tight container to dry, how long does it normally take for your emulsion to dry? And what does that say about how the emulsion was prepped (thinking water content) or how thick the emulsion is?

I ask because it takes several days for my plates to dry in a light tight (and probably air tight) container...even with a container of Damp Rid desiccant in the container to pull moisture out of the air.

Wayne · Jan 3, 2016

overnight. but I just put them in an empty film or paper box, certainly not air tight

ThePhotoChemist · Jan 3, 2016

Like Wayne said, overnight in a container that is not air tight is usually sufficient. My darkroom gets very cold in the winter, which seems to slow down drying; so sometimes I put on a fan to gently move air across the plates.

I tried using a light tight box with a ton of silica gel and a tiny fan to move air around last year, but it never really seemed all that effective for drying.

removed account4 · Jan 4, 2016

I've waited overnight and I have only waited a few hours too. darkroom, not light tight box, And I have used a hair dryer to dry plates too .. but that was 20 years ago.. was store bought liqipuid light ..

Nodda Duma · Jan 4, 2016

Thanks for the feedback. The plates are drying in an unpowered, unused laboratory oven (with wire racks inside perfect for setting the plates on) in a basement with 35% R.H. I have the desiccant inside. So while there's no airflow, the air inside should be very dry. Checked this morning and 1 out of 10 were completely dried. That was two days drying time. I expect most of the rest will be ready tonight or tomorrow.

My theory (based on inexperience--this was my first DIY emulsion) is that I ended up with a higher water content in the gelatin mix that takes longer to evaporate out. Following this recipe: http://unblinkingeye.com/Articles/Emulsion/emulsion.html in Step 8, I may not have poured off enough excess water.

I think I'll test this theory using some of the Rockland Liquid Light emulsion I bought as a control during my emulsion making adventure to compare dry times.

This shouldn't affect sensitivity right? My first plates seemed to run at about ISO 0.5-0.8.

I think I may also try to rig a small computer fan inside to try to circulate air.

Wayne · Jan 4, 2016

yah my plates were with Liquid Light so ymmv. It occurred to me you were using DIY...

removed account4 · Jan 4, 2016

2 days sseems like a long time ..

Photo Engineer · Jan 4, 2016

In an average room at 70F (20C) and 50% RH, drying time can be 4 - 8 hours depending on air flow. With rapid air flow it can be as short as 1 - 2 hours though.

The emulsion depicted is rather slow and seems similar to those published elsewhere. It should be about ISO 1 or 2.

The concentration of silver in the final emulsion affects speed, contrast and Dmax. The concentration of gelatin affects coatability and development as well as hardness in the sense that it can swell unless hardening is complete.

PE

Nodda Duma · Jan 4, 2016

Extrapolating from the drying time in a room, my drying time seems to make sense considering the lab oven has a volume of ~1 cubic meter. If I was smart I'd pour a control plate and let that one dry outside the oven.

Fortunately I can observe when emulsion is hardened by viewing the reflection of the safe light at a glancing angle. It is easy to see the thickness difference between swelled and fully dried gelatin.

Regarding ISO: Checking my notes, I couldn't consistently control the rate of silver nitrate addition during the precipitation stage. The only item I had on-hand was a syringe and a timer. I'm guessing that inconsistent drip rate (I'd have to pause to suck more silver nitrate solution into the syringe) is why I lost sensitivity. I have a note to acquire a setup to provide a more consistent flow (or drip) rate.

Lessons learned for the second batch.

Photo Engineer · Jan 4, 2016

Addition rate affects contrast and to a lesser extent the speed. Temperature, concentration, digestion time and when and how the additions are made all affect speed and to a lesser extent contrast. But then, it depends. Phase of the moon, what t-shirt you have on, the contents of your pockets and whether you went widdershins first!

PE

Nodda Duma · Jan 4, 2016

Funnily enough, I had been doing night testing for work, so I know exactly what the moon phase was (waning gibbous), and I also recall that I was wearing the Tshirt I acquired while at the last International Optical Design Conference. I figured it would be good luck.

It also happens that the beer fridge is in the darkroom....which certainly was a factor as well!

Photo Engineer · Jan 4, 2016

Now you have to figure out widdershins!

PE

Nodda Duma · Jan 5, 2016

I have a head start by being left-handed..

Photo Engineer · Jan 5, 2016

I'm left handed as well, but am also somewhat ambidextrous. This helps.

PE

kb3lms · Jan 5, 2016

I haven't done glass plates but if I leave my coated film out to dry in the darkroom somewhere between 4 and 8 hours is about right. If I set a portable electric heater heater nearby time can be as low as an hour but curl sometimes becomes a problem. Curl wouldn't be a problem with glass, of course.

Nodda Duma · Jan 5, 2016

Last of the plates dried today. Just loaded them in plate holders. I had one which the emulsion didn't stick to the glass, and another which I dropped and broke

So that was a good 2 1/2 days to dry in a 1 m ^3 airtight / light tight container with dessicant.

widdershins were not used in the creation of these plates!

removed account4 · Jan 5, 2016

did you use a sub agent between the glass and emulsion ?
you can use a variety of different things, gelatin or clear urethane works
or nothing except for an extremely cold surface you rest the plates on
... after you coat the glass. ( mark osterman mentions this in one of his notes on photography essays .. )

the worst is getting your hopes up, make exposures
have the negative ( or positive ) look PERFECT in the developer
and then have it float off the glass nd in a long string slide down the drain.

good luck !
john

Photo Engineer · Jan 5, 2016

Subbing is not needed. Mark and I use no subbing and it works fine.

If things are right with the coating there is good adhesion, good drying and good processing. But, you do need a hardener fix.

PE

removed account4 · Jan 5, 2016

Photo Engineer said:
Subbing is not needed. Mark and I use no subbing and it works fine.

If things are right with the coating there is good adhesion, good drying and good processing. But, you do need a hardener fix.

PE

hi PE

really ?

i have had pristine clean glass and without subbing, and with COLD,
the emulsion just floated off and down the drain. unfortunately i didn't
have a guru like you to help, no internet, no books, no nothing but my own
guessing what might and might not work. it was the dark ages of the 1980s !

good to hear takes nothing but emulsion !

Photo Engineer · Jan 6, 2016

Yep, no subbing and no hardener.

Nick and Mark coat hundreds of plates a year, and so do their students.

We all use D-76 or Dektol (1:3), an acid stop and an acid hardening fix.

PE

Nodda Duma · Jan 7, 2016

I used a chrome-alum based sublayer on the first set of plates, and 50% of the emulsions peeled away before development. 80% of the remaining good emulsions floated off the glass during development. I ended up with 2/20 good negatives.

This time around I scrubbed with soapstone, no sublayer. I've only had one emulsion lift partially off after drying. TBD if more do before development.

Other notes: I used basic sodium thiosulfate fixer (which isn't hardening right?) and a normal acid stop. For development, I use Dilution A of HC-110, development time via eyeballing the plate in the tray.

Photo Engineer · Jan 7, 2016

Well, there was no hardener in the process.

I harden with chrome alum as well. It is not used at GEH, theirs are unhardened. We have no problems.

I suggest a hardening fix or a prehardener of 10% chrome alum. Use a wash after the prehardening step.

Peeling away before processing indicates improper cleaning before coating.

PE

Nodda Duma · Jan 7, 2016

What about a prehardener like Kodak SH-1?

That's an academic question.. I have some Kodafix coming in to use as a hardening fixer for these plates.

Dry plate emulsion drying time

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