# A real formula

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• 11-15-2006, 08:35 PM
Photo Engineer
Robo;

Yes, film emulsions are almost always bromoiodide emulsions from about 0.3% - 10% iodide and very large in grain, or from 0.2 - 5 microns in size.

Paper emulsions are usually bromide, chlorobromide and chloride (Azo). Grain size varies from about 0.1 micron to about 0.3 microns but there are exceptions, even with film emulsions.

Paper silver varies from about 500 mg/ meter square to about 5 g/meter square, and film varies from about 1 gram / metre square to about 20 or 30 grams per meter square (X-Ray is the highest).

I hope I got that right. At EK we used a mixed english metric system and I was converting from mg/ft square to mg/meter square and rounding.

PE
• 11-15-2006, 11:07 PM
robopro
OK, give me a day or two to digest that. In the meantime, how do you feel about multiple coatings on glass plates? I guess my question is, using a 'primitive' process with gelatin and hand coating on glass plates, would more than one coat really be of any noticable benefit? Right now I'm using albumen with 4 coats. I've never tried less or more -- just doing it because that's what the formula my friend gave me said to do, and it makes sense because you drain the excess from a different corner of the glass with each coat, so common sense tells you 4 coats would give you a more even total coating. If I switched to gelatin, would I see any real advantage to multiple coats?
I have to ask these stupid questions because I'm not a chemist and I need things explained to me in 'easy' terms. If you say mix 6 grams per 100 ml and add 4 ml of 1% solution, I understand that. When you start saying add 26% of 2% strength per 1.5 moles -- factoring in surface area and total volume...uhm, OK, what was that again?
I asked a question once about building a 'simple' lens for my camera and people went off on discussions about refraction coefficients and diopters. What the heck is a diopter? (Do you believe I can actually develop my own prints? I just follow the formulas and procedures that come with the materials -- I really have no idea how they work...) :-)
• 11-16-2006, 10:03 AM
Photo Engineer
A simple answer on glass plates then. With silver halide in gelatin, you only need one coat. Pour the emulsion onto the center of a warm plate and rock the plate until it is evenly coated. Let the excess drain evenly from each corner by tipping all for corners down in turn and then let dry. That should do it.

Do not coat unwashed emulsions on glass plates. They will not adhere. Use an aldehyde hardener for best hardening and adhesion. If you have problems, a gelatin under coat will help.

Make sure plates are dry and free from oil before coating.

A bit of Everclear (ethyl alcohol) and spreading agent will help the coating.

PE
• 11-16-2006, 05:19 PM
robopro
I think I'm about ready to give this a try. I have some experience coating glass with albumen -- which is probably thinner than gelatin. I think the rest I'm just gonna have to learn by doing. Time to start rounding up suppliers!
It'll be interesting to see how handmade gelatin negs compare to albumen.

This whole adventure began because I had this crazy idea about sensitizing albumen to infrared, but the speed is just too slow with ULF pinhole. I put the IR idea on the back burner for now, but I would like to be able to do 11X14 pinhole portraits, and looks like gelatin is the only way I'm going to get the necessary speed.
I'll keep the forum uprised of my progress, if anyone's interested...
• 11-16-2006, 05:30 PM
dwross
robopro:
re: if anyone's interested...

Very much so. Thank you for sharing your explorations.
• 11-16-2006, 06:46 PM
Photo Engineer
Quote:

Originally Posted by robopro
I think I'm about ready to give this a try. I have some experience coating glass with albumen -- which is probably thinner than gelatin. I think the rest I'm just gonna have to learn by doing. Time to start rounding up suppliers!
It'll be interesting to see how handmade gelatin negs compare to albumen.

This whole adventure began because I had this crazy idea about sensitizing albumen to infrared, but the speed is just too slow with ULF pinhole. I put the IR idea on the back burner for now, but I would like to be able to do 11X14 pinhole portraits, and looks like gelatin is the only way I'm going to get the necessary speed.
I'll keep the forum uprised of my progress, if anyone's interested...

I'm very interested, and if I ever scare up an IR dye, I'll help you get started on that.

NOTE: To Simon Galley.... There is a market for this stuff. EK won't believe me, but here are 2 customers already. I'm sure that there are more.

PE
• 11-16-2006, 10:29 PM
25asa
xenocyanine is an IR dye

Neocyanine is available from Cole-Parmer \$88.50 for 1/2 gram.
3,3'-Diethyloxatricarbocyanine iodide is 107.25 for 1/2 gram
• 11-16-2006, 10:41 PM
robopro
so is 3,3'-Diethylthiatricarbocyanine iodide, available from Sigma-Aldrich for \$56.00 per 1 gram bottle.
• 11-16-2006, 10:51 PM
Photo Engineer
Try H. W. Sands Corporation in Florida. They worked with EK. Also, you might try Honeywell in Germany.

But, I can't tell you everything, now, can I? Oh, I already have! ~grin~

Actually, I have Paul Gilman here as a resource to help me with dyes, and I'm not ready for IR dyes. I'm still back working on Ortho.