With apologies, I see what happened in some previous posts....
This is a typical exposure on an 8x10 sheet testing with the Stouffer step wedge, 2 resolution charts and a normal photo.
In some previous posts, I had cropped the scan of the prints to illustrate the resolution charts and in another case to illustrate the contrast but I had not shown all 4 in one print.
Right now, I have 3 of the prints here, but cannot locate the full scan of the Ilford, nor the original print. The 4 print set got separated somehow. When I can, I will repost as much as I have here, but the exposure here is pretty typical of how I test my print emulsions.
If anyone wishes to see the film tests, let me know. It is just about the same as this though except shot in a camera.
Thanks, Ron. I'm glad you found the whole step tablet (I was wondering ) I see you are still having surfactant problems (unless these are the same prints from four years ago - they look familiar, but I know you follow the same basic research protocol I do, which is to re-use materials to keep an established baseline.) Keep up the good work. Post often!
I think a lot of things are coming together, each of us in our own areas of particular interest. I can hardly wait to see Ron's superspeed films. Bill Winkler is having very good luck with ortho emulsions and is well on his way to pan. If I were a betting woman, I'd bet Kirk will be busting open the T-grain puzzle soon. I'm almost ready to go public with hand-subbed film, which should make the 'capture' side of emulsions a lot easier. With apologies to Bill, as beautiful as glass is, a backpack full of dry plates is a load going up a trail!. And of course, there's Tim's great work with paper. I hope 'hrst' and 'totalamateur' haven't given up. I can tell you that I'm in regular contact with a number of people who have started working with emulsions, but are too shy to share just yet.
On a tangential note, I submit a gentle elbow nudge to lurkers. I see that there are many more hits to this thread in the last hour or so than views of Ron's jpegs. If you are just lurking here without membership jpeg privileges, you're missing half the fun. It's free and painless to sign up as an APUG member. You can always decide to support the site with a subscription later.
Please note a patent by Yost of Kodak that describes fog formation by corona discharge and methods to prevent it. I was not aware of this until I did a recent search. Dick Yost's work should have stuck in my mind, but it was so long ago.
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Several questions for PE & others
I would really like to make smaller batches of Denise's paper emulsion. I can handle scaling the ingredient quantities, but I'm unsure how to scale some variables, such as silver addition. Could anyone make suggestions or does this require elaborate and expensive control devices. I am using a stopcock buret and a timer to add silver nitrate. How about other variables, ripening, digestion, and etc.
A while ago I read some info on using rice starch to make a matt paper surface. I though I read it here on APUG, but can;t locate it for the life of me! Actually, I thought it was a post by PE. If memory serves correctly, the info described warming the starch until the coagulum settled to the bottom. This was then used as the matting agent in the emulsion. Well, I might be just full of it, but I would really like a matt finished paper.
If you scale the emulsion just multiply all volumes by the scale factor. This works between about 100 ml and 500 ml. After that, you need more vigorous mixing in the form of a magnetic stirrer on the bottom and a prop mixer in the middle or the solution viscosity (gelatin) will mess up the make.
Keep everything else constant. Keep addition rates and hold times the same. Heating things up and cooling them move more slowly and you will need to speed them both up.
Starch is a good matting agent, but I didn't bring it up. Someone else must have. Your comments are right about on. Modern coatings use Poly Methyl Methacrylate beads suspended in gelatin and that is about the same as starch in gelatin. It should work.
Best of luck.
With apologies to Bill, as beautiful as glass is, a backpack full of dry plates is a load going up a trail.
No apologies called for. Its all a matter of philosophy. When I am doing "Art" and not "Research",I will spend 3-4 days getting 4 shots. OTH, I know very good photographers who shoot hundred of shots in a day, then a week editing, looking for "the Good one".
Dry Plate Bill
Some new progress to report!
Thought I would update this thread with some notes. But first I want to say a big Thank U to everyone for the help and encouragement.
Had a chance to work with my first batch of emulsion this morning. It’s now four weeks old and starting to exibit a lot of peppering. So now I can use it under white light to prefect my coating technique; it’s fubarred anyhow.
I coated several test sheets of Fabriano, but first humidified them above water for about, well I took a nap, so a long time :rolleyes:. Anyhow I guess they where like 100% humidified. The paper was flat, soft, and ready to accept the coat. Of course the emulsion still floated of in the final wash, but not as badly as other test pieces.
I really like this paper, it dries flatter, has better contrast, is brighter, and I just like it better than Arches. Two different papers with the same emulsion is a nice idea though.
Did a little searching on the net looking for info on a chrome alum fixer and found this on Google form “The Focal Encyclopedia of Photography.”
Chrome Alum 12.5 g
Sodium Metabisulfite 12.5 g
Sodium Sulfite, anhydrous 6.25 g
Sodium Thiosulfate 400.0 g
Water to make 1.0 L
adjust pH to 4.0 – 6.5
The amount of sodium thiosulfate seemed high to me so I cut it back to the more common 24%. Not sure that was the right thing to do. I guess I will have to do some residual silver testing. Maybe PE could comment or improve upon this formula for us.
…And the emulsion now sticks to Fabriano.
Hopefully, this week I will have the time to make a new batch and coat it all in one go, on both Arches and Fabriano paper.
Just for giggles, measured pH of solutions.
Ansco 130 (10.1)
Metabisulfate Stop Bath (5.0)
Chrome Alum Fixer (4.9)
Today’s tap water (8.0)
My Humidifying Chamber
Very simple. Go to Lowe's or similar DIY store and get a sheet of egg crate diffusion material made for in ceiling fluorescent lighting and also some fiberglass screen. In a suitable sized developer tray lay several layers of paper towels. Pour hot or cold (your choice) water over the paper towels and then pour most of it out. Lay the egg crate material on the damp towels and a sheet of screen on top of this. Lay your paper to be humidified on the screen. Finally, cover the tray with something like a sheet of plexiglass to keep the moisture in.
Mike Ware describes the method on his web site with info on how to exactly control the amount of humidity using various salts.