Some pre-emulsion making questions . .

Hi To All,
Prior to every new batch of emulsion, I pray to the God of Emulsions for a good batch. No matter what one's Belief System, this cannot hurt ! Heck, It worked for George Eastman !
Bill

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Originally Posted by dwross

Do you ever watch Big Bang Theory? The guys in the comic book store arguing about story arcs?

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Yeahhh! Another Big Bang Theory Fan? !!

(a few days ago I was looking at it with French subtitles-
and last night I was enjoying it in German!)

Somehow I felt it was funnier in English but that is probably more related to the vocabulary used... I know most all the shows by rote.

Anyway, thanks for the smile...

PS
Not everyone's bread tastes the way it should of could of would of!
I often find fault with Baked goods... even those that seem to be selling well.

The slight disagreement on ammonia may, in additon to the points made by Ron, also relate to different degrees of complexing, actual treatment times and the specific Rx, &c.

But yes.

Hi,
As a 3rd (at least) generation chef/baker (the first one to not make a living at it) I must say that ,beyond all argument, the specific flour one uses makes a big, BIG difference in whatever one bakes. The only people who cannot appreciate the differnces are those who were raised on Wonder Bread and who are not interested in exploring anything that their parents did not teach them.
At the begining of my emulsion making days I was elated just to get an image. It took 5 tries befor I overcame severe fogging. But that must have been just me. The longer I do this the more obsessive- compulsive I become.
Cheers,
Bill
P.S. I have never even heared of a TV program caled The Big Bang Theory. Who was the Observer of the "real" Big Bang?

Yes, well be that as it may, the attached image from a glass plate is from an emulsion that was made at 50 deg C and used ammonia. It was an SRAD. Denise has this formula. This photo was shot in a Speed Graphic at ISO 40 and processed in D-76 for 11' at 68 deg. The hardener used was a mix of glyoxal and chrome alum. I have made this formula up to 60C.

PE

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P.S. I have never even heared of a TV program caled The Big Bang Theory.
Who was the Observer of the "real" Big Bang?

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See:
http://en.wikipedia.org/wiki/George_Smoot

Read the secton on COBE and also look at the section "Public appearances"

Well, OK. I think the answer to your question might depend upon where Adam's Dad was... and if he was looking in the right direction! :D

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Originally Posted by Photo Engineer

Almost any red safelight that works for your enlarging papers will work for your hand made emulsions. A film emulsion generally has a lower contrast than a paper emulsion by the very nature of things. So, it gains its speed and lower contrast by having a slower addition time of silver to salts. Higher temperatures increase speed and lower gelatin increases speed, but if you go too high in temperature (~80C) or too low in gelatin (~1%) you will get poor results.

Plan on coating your emulsion between 5 and 10% for best results.

PE

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Just wondering if you've mixed silver halides formed at different temperatures together?

Athiril;

I have done that at Kodak. As long as the surface iodide is the same, there is no exchange in halide, so it might be a 10% iodide and a 5% iodide, but if both are core shell and they have the same surface, ie pure bromide or 1% iodide, mixing them has no adverse effect. Temperature has no effect whatsoever on the mixture. Crystal habit has no effect on either emulsion.

PE

I have made this formula up to 60C.

PE[/QUOTE]

P.E.,
In case you misunderstood, I was agreeing with you.
Bill:D

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Originally Posted by Kami-the-Trout

I'm about to give a go at making a basic emulsin to coat on glass for my 13x18 plate camera. I've assembled all the bits and pieces (including a magentic hot plate stirrer) and have a coupe of questions.

1. If my darkroom safe light (red) is safe enough to not fog paper for several minutes, is that dark enough for emulsion mixing purposes? How do I know if the light is OK? I don't want to mix in the dark . . . :)

2. All the recipes say to add silver to the gelatin slowly, to increase the speed. A quick dump increases contrast at the expense of speed, as I understand it.

If I like the idea of contrast more than speed, is it OK to do a quick add? How slow would that likely make the final product? Any idea?

3. There are a variety of recipes to try, each with slightly varying amounts of silver nitrate to gelatin to pot. bromide/iodide. Is there a guideline that suggests more silver is better/worse, contrasty/less contrasty, faster/slower, etc? I'm trying to decide which recipe to do first.

4. Most recipes call for thymol as a preservative. I don't have that yet. Is it absolutely crucial, or can i do a batch without it, and still expect some longevity from the emulsion? Or should I wait until I get it?

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The advice already given is far more knowledgable that I could give, but I do have the experience of a novice trying to figure it out.
1. Don't worry about your safelight. My emulsion takes 1 minute of a 1watt red LED set on the emulsion iteslf to fog.
2. I think you will find the contrast satisfying even with a slower dump. My contrast is more dependent on the quality of coating than the makeup of the emulsion. ( I guess, to be technical, that would be Dmax, rather than contrast, I find my emulsion similar to the Arista Ortho Lith film when developed in continuous tone developer. I find the quality of the coating has far more to do with the final print than anything else)
3. I've tried PE's SRAD and a few others. They all take pictures, my advice is to pick one and get some practice coating it and making reproducible results.
4. While others cite shorter lifespans, I've left coated plates in room temp for over a month with no discernable difference in the quality of the neg and I use no preservative. I don't think preservative is critical.

We made PE's "A real formula", ammonia at 60C, and it worked very well. We even used food grade pig skin gelatin sheets and self-made silver nitrate (at least 99.9% pure silver dissolved in nitric acid).

We liked the contrast and curve shape. It printed well on normal contrast grade on Kentmere Multigrade paper. I've attached a scan of a print made from 35mm frame of this emulsion. The speed was below ISO 10.

Safelights;

Orangish-red leds fogged our erythrosin-sensitized emulsion. 1 hour from 1 m distance was enough to do it. So, better be too careful than not enough careful. Deep red would probably have been totally safe.Without spectral sensitization this is probably much easier. There might have been also another reasons for fogging (overwashing and higher temperature)