I had an opportunity yesterday to play around with your 'problem'. I used some slightly thinned-down polyurethane as a polymer substitute. The thicker surrounds, with their edges jammed tightly together, and pressed tight to the silicon sheet, held the urethane just a tad higher than the glass plate until things dried. It's an imperfect test, of course. Viscosity and drying times are sure to be different, but I think it's worth the effort for you to invest in trying the thicker glass for emulsion-dam pieces.
One thing I didn't know how to test was how easy it will be for you to cleanly separate the dried plate from the dam pieces. With the urethane, when everything dried, I lifted the whole assembly off the silicon sheet and threw it away. (Not worth the trouble to clean off the urethane.) With gelatin emulsion, the dam pieces can be easily loosened and cut away without cutting through the silicon sheet. Be careful with that when you test your polymer emulsion. The silicon is a super release material, but it is easily damaged with a sharp knife.
As far as applying the emulsion: pouring or squirting (my preference) it in the center works with formats that are close to square. Perfect for 4x5. With the more pano formats, you have to start the emulsion at one end and pull. Gravity alone won't cover the surface. The last time I coated pano (5" x 12") I used an emulsion well and puddle pusher, but I'll be trying it with the emulsion-dam system soon (same thickness edges and a wrapped-up puddle pusher.) Michael's results indicate it'll work just fine. http://www.thelightfarm.com/Map/DryP...latePart4b.htm
We're just going to have to get you started on making your own plate emulsions!
If I use thicker glass edge pieces, I draw down with a glass rod without any tape; If the glass edge pieces are the same thickness, then there is tape on the ends of the glass rod. Both methods use the edge pieces to stop the emulsion next to the plate. The glass is best preheated in both cases, not much, but not cold. I use a hair dryer before the emulsion is dumped out.
Originally Posted by wildbillbugman
[QUOTE]We're just going to have to get you started on making your own plate emulsions!/QUOTE]
Yes, I would like to do that. The Light Farm has a lot of great material to read on the subject. I've now started my readings there about emulsions; much was printed out; each section is marked in pencil as to how many times I've read it; I need to read things like this 10x to understand but I've started. I like how the older writing has tips not included in the rewrites; they are well worth reading for that information. A lot of lab equipment is needed, but I am scheduled to have new motorcycle tires put on; there goes that check; the MacBook Pro payments ate the rest of the money, and will for a while longer. I hope that by the end of the year I am making emulsions.
Hi Denise and all,
It will be an unknown period of time befor I can make another emulsion. I do not have anymore R-Polymer and B&S have not received their order yet. I see no reason to go back to using home made subbing, unless the Kurraray thing falls through completely. But I have a couple of questions-
Why do I need a space between the plate and 2 of the Dams. Denise's concern about not being able to separate the plate from frame is well founded. The emulsions dry hard and tough, and adhere to the glass like baby sh-t to a blanket. I absolutely Will have to use a blade. I am thinking that a blade sheved in such a way that it dose not penetrate down to the silicone sheet would not be hard to do. I can see the advantage for a space for cuting. But it could be ever so slight, and not required at all. with elavated dams.
If my emulsion dose not set up like gelatin, do I still need to preheat the glass?
Well, if you come to Rochester on your 'cycle as you threatened, you can be ushered into the world of emulsion making quite gently and easily. We would welcome you here of course.
We're just going to have to get you started on making your own plate emulsions!/QUOTE]
Yes, I would like to do that. The Light Farm
has a lot of great material to read on the subject. I've now started my readings there about emulsions; much was printed out; each section is marked in pencil as to how many times I've read it; I need to read things like this 10x to understand but I've started. I like how the older writing has tips not included in the rewrites; they are well worth reading for that information. A lot of lab equipment is needed, but I am scheduled to have new motorcycle tires put on; there goes that check; the MacBook Pro payments ate the rest of the money, and will for a while longer. I hope that by the end of the year I am making emulsions.
If your vehicle does not set up, you probably do not need to use a heated plate unless you desire to adjust viscosity by heating.
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Thanks for the feedback and motivation for getting back to writing on TLF. I need the kick. Like any artist, I get in phases when my own work seems far more compelling than just about anything else! But, I'm within days of starting on a 2nd ed of The Light Farm.
Each time I do an update, I stew and fuss about the right way. I love web instruction formats, but something is being lost in the current SOP for web publishing. That something is history, even very short histories. Back in the paper-between-cardboard days, 1st editions would stay on the shelves alongside the later versions. Invaluable. How to do that with a website as dynamic as TLF has been a puzzle I've just recently sorted out. Stay tuned .
You might very well not need much of a gap. The idea behind the gaps with gelatin emulsions is that the emulsion flows over the edge and fills up the gaps and then stops flowing. If you apply the right amount of emulsion (I use a catheter syringe) there is almost zip waste and the emulsion dries perfectly over the entire plate in the same thickness. Note: there's a caveat here: the coating/drying surface must be dead flat. If your surface is almost flat, you might not be able to tell until the fixing step. One side of the plate will clear before the other -- almost never a problem, though.
I'm guessing, of course, because I've never used your emulsion, but I don't think heating is necessary. Even with gelatin emulsions, I don't pre-heat my glass. I keep my darkroom at 70F, and know the right coating temp for a given emulsion. The room temp glass is actually a part of my 'process' (too grand a term for something as simple as the way I've been coating plates). By the time the emulsion has filled in the gaps around the plate, it is starting to set up.
Hope you get your R-polymer soon!
Denise and all,
Just had a thought. I wonder what would happen if you used teflon sheets insted of glass for the frame. Seems like it would repell the emulsion and whatever you pored or syringed onto the plate would stay on the plate. This might work even if the frame is the same hieght as the plate. Teflon sheets are availible in all thicknesses. But it occured to me that if this worked Denise would already be doing it.
Actually, Teflon has occurred to you before me I haven't gone beyond silicon and glass. I had a silicon baking sheet in the kitchen I'd never used, and like so many things from my kitchen, it winged its way to my darkroom. Worked so well, I bought it a bunch of brothers and sisters. Glass.. well, glass is glass. For gelatin emulsions, the two surfaces work so well (and are so readily available and inexpensive) I suspect I won't be inspired to test other materials. I did have to search around a bit for the right kind of silicon sheet after the kind I originally used stopped being sold. I've settled on the Target brand. I think it will be around for awhile, but I have bought a couple of spares anyway.
Your polymer emulsions are so different from the gelatin-based, that Teflon might indeed do the trick for you. Unprocessed gelatin emulsion is easy to remove from glass. Do I remember correctly that the R-polymer really dries tight? If you went with the Teflon, you'd need to mill out plate-sized squares from the center of the sheets (???).
I wonder if the teflon frame would slide around on the silicon backing. If not, I was thinking in terms of teflon strips, like the glass strips that you use to construct each of your frames. I was not thinking of cutting a rectangle in the middle a teflon sheet. On the other hand, if I can find a cement or glue that would adhere to teflon, I could contruct a dozen permanent plates, with even the base made of teflon. As I am writing this, I am liking the later more and more.
Love to Maggie,
Originally Posted by wildbillbugman
Poor mutt! She's very disappointed in me. I know she thought I'd finally decided to stay out the 'evil room' and spend all my time taking walks like a sane person. Now that I'm back in the darkroom, she's taken to sitting right in front of the door -- waiting. Every time I come out, she's sitting there, staring at me, as only a Sheltie can stare!
I just tried sliding a Teflon baking sheet on a silicon baking sheet and it didn't. Now you need to find the right adhesive. I like these people. They were wonderfully helpful when I was looking for the right glass adhesive.