With such basic questions, I think you should step back and study a bit before you jump in. This is the deep end of the pool we are talking about despite what Denise says. I agree that it is not hard, but if you cannot understand some basics of photography and chemical mixing, it isn't an off the shelf cake mix.
For example, there is no relationship to what we are doing and permawash so don't even try to make the connection.
As for coating, figure about 6 ml of emulsion / 4x5 glass plate or 12 ml of emulsion / 8x10 glass plate.
I'm going to start with 4x5 just to make things a bit easier.
Originally Posted by Kirk Keyes
Thanks, I always get Hypo and Hypo clear mixed up...
Originally Posted by Kirk Keyes
One of the most common confusables in photography. That and f-stop numbers. It took me the longest time to internalize big is small Reciprocals and all that math nonsense (should have paid more attention in arithmetic class.)
Originally Posted by EASmithV
There's nothing to fear at the deep end of the pool if you keep a few flotation devises handy. I highly recommend Steve Anchell's 'The Darkroom Cookbook' and E.J. Wall's 1912 'Dictionary of Photography'. That's available as a Google Book:
It's amazing how much of the vocabulary we use today has come to us from 100 years ago, so an old dictionary is fun and useful even if you're not interested in making old emulsions. For those of us trying to time travel in our darkrooms, the old volumes are invaluable.
Here is Mark Osterman's ISO 3 - 12 plate emulsion, courtesy of Mark, for your enjoyment. It has been posted here before, but I had to look it up so here it is.
This formula will give an ISO 3 – 12 formula suitable for coating on plates. It is used by GEH (George Eastman House) for teaching purposes. It is a very early SR formula. I would like to thank Mark for permission to include it here.
• You will need:
Everclear (95% Ethyl Alcohol - NOT DENATURED)
Add 2.6 grams of gelatin to 84 ml of water and allow to swell, and then heat until melted. Add 10.3 grams of Potassium Bromide and 0.6 grams of Potassium Iodide. Bring to 120 deg F.
Dissolve 12 grams of Silver Nitrate in 84 ml of water. Heat to 120 deg F.
18 grams of gelatin with excess water to swell (this should be kept below 68 deg F or the gelatin will begin to melt prematurely)
Add B -> A in a fine steady stream with magnetic stirring.
Heat for 15 minutes at 140 deg F.
• Final prep and washing:
Drain the water off the gelatin in solution C and when well drained pour the emulsion over the swollen gelatin. Mix well then heat until all of the gelatin is melted and well mixed. Chill set. You may then shred the emulsion and and wash for 30 minutes with 3 changes of distilled water.
Add 4 ml of 5% Chrome Alum and 5 ml of 95% Ethyl Alcohol (Everclear). You may add one grain of Thymol as preservative. Coat at once on glass plates.
These plates can be used in-camera or to make lantern slides.
Thanks for posting this PE.
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Ditto from me. Give Mark our appreciation. This is an important contribution.
Originally Posted by Emulsion
I'm going to post a link to this thread from my website, and I hope others do the same. A lot of irreplaceable information is posted on APUG, and in such a casual way sometimes that the value of it can be underestimated by folks just passing through. I love the internet, but I worry a bit about information like this being lost again - the electrons drifting off into the firmament. The best guarantee I can think of (besides going through reams of copier paper and gallons of toner) is to cross-post in as many places as possible.
An additional note of interest on this recipe. It is included in the 2nd edition of Christopher James' book on alternative processes, http://www.christopherjames-studio.c...d/thebook.html
Originally Posted by Photo Engineer
Thirteen pages of information on gelatin dry plate have been added since the 1st ed. The pages include detailed instructions on the process, with illustrations courtesy Scully & Osterman Studio.
The instructions and illustrations are well done (overall, it is an excellent book), but many of the details differ from my observations and practice. Since I would never second-guess Mark Osterman, it is clear there isn't 'one right way' to make an emulsion. Anyone really interested in learning to make emulsions should try as many techniques as possible - all the while determined to put her/his own spin on things. A personal, hands-on comparison of your own plates will teach you more about emulsions in the beginning than will all the theory you can read. Theory will carry you forward after you've started, but it's definitely the cart, not the horse.
A case in point ready at hand is the difference between Osterman's recipe as posted here on APUG, and the recipe as published in James' book. The proportions of KBr and KI differ, as do a few of the making details, probably enough to change a bit the end character of the plates. You couldn't ask for a better early lesson on emulsion making than to try both.
And here ends my Saturday Soapbox