Dry plate emulsion help

[Elrin]

I'm trying out the dry plate process and used Mark Osterman's recipe. Everything seemed to work out fine until it comes time to coating the plates. They are washed and subbed and when I go to coat them, it doesn't spread evenly and almost looks like little bits of undissolved gelatin are in the emulsion once it begins to firm. So just to make sure I passed the emulsion through a fine-mesh sieve and it all passed right through, no problem. So I went to try and coat again but again, uneven coating (some of the emulsion will set quicker and/or when I go to tilt the plate, the emulsion is runny and doesn't properly coat, etc). Does anyone have any ideas what might be the problem? I rather try to use/save this batch rather than make another one if possible. Thanks!

 

[Peter Schrager]

is the setting where you coat level?
I think a block of some sort of stone might be the way to go for coating. the emulsion will coat faster on a cold surface

 

[Elrin]

Yeah I checked it and was perfectly level and it is a stone in my basement so nice and chilled. I tried a new plate and syringe and the emulsion stays right where I squirt it. It's also when I slowly try to tilt it to have the empty areas fill in that is seems to run rather than "flow" and sometimes seems like the gelatin part starts to set but there's a layer of runny liquid still on top that displaces the partially set gelatin.

 

[Nodda Duma]

Dilute your emulsion some with distilled water... it sounds like it’s too high a concentration of gelatin to give you enough time to coat the plate. Calculate concentration by amount of gelatin you used / total volume when you finished.. I bet you’re up around 8-10% or more but that’s just a guess. Add water to make that about 6% or so. You’ll need to take into account how much you’ve used already. Work faster when you coat (hint After squirting emulsion onto it, you can smear the surface with your finger to wet the entire plate with emulsion, then tip/tilt to distribute the bulk)

This should help quite a bit.

 

[Elrin]

I'll try that. But if the emulsion seems loose/runny now when I tilt the plate to coat, wouldn't the extra water make it even more "runny" and more difficult to control the flow?

 

[Nodda Duma]

It should be a fair bit runny. Somewhere between water and dish soap. The working time will be longer — like a minute or so — and that’s what you need.

 

[removed account4]

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[Peter Schrager]

man, I love this website.

we love you too!!

 

[jkharrell]

If you're using Chrome Alum as a hardener, if you add it too fast and not drop by drop, it can seize up the gelatin. That could explain the chunks. In my experience the glass plate should be warm until you've finished coating it, otherwise it will set too fast on the cool glass. I warm mine on a hot water bottle covered with a dish towel. I coat a plate the same way as coating a wet plate with collodion. I place it on my fingertips and pour a big puddle in the center almost to the edges of the middle of the plate. I let it run to and fill all of the corners by tilting it slightly each direction, and then drain a bit from one corner. I then immediately tilt the plate in the other direction and let it drain a bit of the opposite corner. Once I've drained the excess, and don't drain off too much of the emulsion otherwise the edges of the plate will lose density, I place it onto a large cool glass/stone plate to chill before placing them in a drying box.