Rick said:
I did ask a previous question as to if the system would work with an Albumin medium. Is there a difference in viscosity between the two materials that would make a difference in using the tool for Albumin?
As for size, it pretty much sounds as though one's tool selection is going to be based on the size of paper one plans to standardize on using. Kind of like a matched set?
Your class outline does sound interesting, and at least for me, very much approaching rocket science!
By the sounds of your post, I think you're implying that the learning curve is going to be longer than a weeks worth of sessions in the darkroom!
Rick, sorry, I didn't give a full answer.
Here they are for each paragraph:
The blades work with anything that has viscosity. Therefore any polymer or albumen etc. will work, as long as you give it sufficient time to rest after coating to just set up a tad before moving. This is usually on the order of just 10 - 30 seconds but can be as high as a minute with very low viscosity, dilute gels and polymers. I have never used this for albumen though, so I cannot speak either way, but I have used it for lots of polymers at EK and I've even coated from solvents under a hood. You don't need to just use water if you have the right facilities.
The tool size is based on what size(s) you wish to coat. I would get one the maxiumum size for my work. IDK yet. Give me time. I may change that for the purposes of yield. If you do 4x5 and 8x10, you might get a better yield from 2 blades rather than one larger blade and cutting down the 8x10s. I have to get the yield up on the 8x10s and to do that I need the new redesigned end cap and blade set. Give me a few weeks to test things out at the larger sizes. Also, I don't even have the 11.25" blade yet.
I guarantee that the class will not be rocket science, This will be dump and stir for the darkroom hobbyist. I want to make this as painless as possible and as non-toxic as possible (there will be a few exotic chemicals that no one has ever heard of before (well, no one normal that is - just us abnormal photo engineering types), but nothing like mercury or lead).
The learning curve is not weeks or months, more like days or hours depending. I just don't want people going into the lab and wasting silver. That is just too expensive. I want it to be simple and easy time after time, once you learn the routine. I myself had not done any in years having turned into a desk jockey in my last years at EK, but going back to this was a simple job once I had the right blades. Once I had them, I was turning out 90%+ yield of 4x5s in one night after one afternoon in the light practicing.
Here is a simple test that anyone can perform to test their coating quality for a viscous system:
Dissolve 10 grams of photo grade hard gelatin (Bloom Index 175 or higher) in 84 grams of water at 40 deg C and heat until it becomes free of lumps. Add 2 grams of Red, 2 grams of Blue and 2 grams of Green food color and stir until mixed. Add to this, 6 drops of Kodak Photo-Flo 200 (see below). Use this to paint, pour, puddle push, or otherwise coat your paper, film, plate or whatnot. If you want to harden this, add 20 drops of 10% glyoxal.
You should get an even coating possibly with some small craters caused by the interaction of the food dye with the surfactant (called repellancies and mentioned in another thread on coating sulfonic acid couplers). I have not tweaked the surfactant yet for this test, but it will show up gross unevenness and coating marks. It is a measure of your coating technique.
This test makes a good starting point for judging your coatings for quality. If you get too many coating streaks or repellancies, there is either too much or too little Photo-Flo. Therefore, I suggest that you start at zero with the PF and add it dropwise with stirring and testing the coating mix above to get to the sweet spot. It differes with food dye and with batch of gelatin and with Bloom Index. The value above is an approximate mid-point for my current conditions. This uses a 'new improved' viscous food coloring. My previous batch of food colors was liquid and didn't use the same balance of surfactant. It also coated better.
This test works with any polymer or albumen when coated from water. I don't know how well it works as far as hardening is concerned except with gelatin.
Reflection or transmission density measurements will give you an estimate of uniformity, or just the plain Mark I human eyeball test will do well with this.
The goal is to have the exact same density from side to side and end to end of the sheet with no streaks, scratches or lumps. The repellancies (little round craters) don't count.
PE