Some pre-emulsion making questions . .

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?

Hi Kami,

First: Congrats! on taking the plunge. You're going to have a blast.
Here's my take on your questions:

1) If you mean commercial enlarging paper, I'd say you're probably safe. It's tricky, though. I had the same little red safelight for years; the incandescent kind covered with red film. It worked great. When it finally blew I could only get one that was covered in what looked like red paint. It took me three weeks to figure out it was a fog machine. I replaced it with a string of tiny LED Xmas lights. My darkroom is lit up like it has a red sun and I've never fogged anything since. There is no reason to work in the dark.

2) Given mid-day summer sun (i.e. good UV light), you won't go much lower than ASA 3 or higher than ASA 25 with a basic bromide emulsion without extra sensitizers. They are inherently contrasty. The speed of addition, combined with the temperature and the amount of mixing during ripening, influences grain size (i.e. 'speed'). You can push up the speed a bit and lower the contrast a bit without risking heat/ripening fog, but mostly it is what it is. If at some point you want to try for more speed or a smoother density scale, I've found that divided additions is better and more predictable than adding one addition slower. Make sure you follow the temperature recommendations and don't let the heat climb too high with an emulsion recipe that calls for ammonia.

3) The amount of silver to gelatin is mostly about how thin you can coat your plates and still get decent density. Again, the best advice is to follow the recipe exactly the first couple of times and then try a few changes to see what works technically and aesthetically for you personally. With the old recipes, I think it's best to start out rich. A higher % gelatin will be easier to handle while you are learning. Gelatin is essentially free and a gram or two difference in silver won't have much effect on the cost of making the recipe. When you start to customize your recipes the only trick is to remember to change the silver and the halide in the same proportion.

4) You do not need a preservative. Your emulsion won't be sitting around in the refrigerator long enough to grow mold! Don't fall for the temptation to make big batches. Your learning curve will be a beautiful thing to see if you make many, frequent recipes. And, if you screw up one, you won't waste more than a couple of bucks .

The best of luck and fun,
d
www.thelightfarm.com

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

Ron,

I think your goal of brevity (usually an admirable goal!) resulted in a couple of typos. As a general rule, decreasing the silver addition rate will lower the contrast of an emulsion. Also, 80C is almost certainly too high for an ammoniacal emulsion, the most commonly encountered type in old film recipes. 40-45C is about as high as I'd want to go to avoid fog.
d

Denise, boiled emulsions at 95C were common in the early part of the last century. They were not ammonia emulsions.

Since ammonia was not mentioned, I used that example, as temperature is a valid "knob" with or without ammonia the absolute upper value depending on ammonia. I make ammonia emulsions at 60C without fog problems.

I made the correction to clarify my remarks. Thanks.

PE

Well, I can see right now that I spend waaayyy too much time with my nose in dusty old emulsion books. I'm becoming a fact-checking, fact-arguing geek . Do you ever watch Big Bang Theory? The guys in the comic book store arguing about story arcs? J.M. Eder in 'Modern Dry Plates', 1881, describes ammonia in emulsions. He talks about keeping the temperature not much more than 40C, but notes that Capt.Pizzighelli (Captain Sweatpants!) claims the character of the particular gelatine employed "exercises considerable influence.., while one sample of gelatine will stand digesting for fifteen minutes with ammonia at 70C, another will produce a foggy emulsion if a temperature of 50C be employed." (p21) And, further up the timeline, both Baker and Duffin recommend 40C-45C.

From all that, I'd say you might have been lucky with fog. A novice just starting out might be advised to err on the side of caution and keep the temp low.

Geekfully submitted for your consideration,
d

Denise;

Inactive gelatin has leveled the playing field in a sense. Also, they never heard of TAI. I suggest that you check the class notes.

PE

Kami,

Pay absolutely no attention to all this nonsense You'll make a beautiful emulsion. Think making bread: You can bake a delicious loaf with all-purpose flour from the grocery store, or you could listen to a couple of obsessive-compulsive foodies argue blue about the relative virtues of high mountain spring wheat from Montana vs. Tuscan something-or-another. They just might drive you to Wonderbread!
d

Very good Denise.

I don't disagree in one way, but I do in another.

Best wishes.

PE

dwross said:

Kami,

Pay absolutely no attention to all this nonsense You'll make a beautiful emulsion. Think making bread: You can bake a delicious loaf with all-purpose flour from the grocery store, or you could listen to a couple of obsessive-compulsive foodies argue blue about the relative virtues of high mountain spring wheat from Montana vs. Tuscan something-or-another. They just might drive you to Wonderbread!
d

Click to expand...

Thank you both for all the advice! It is appreciated.

And Denise, especially, thank you . . . I've spent hours at the Light Farm reading and rereading all your info. It's what given me the confidence to give this a try.

I've decided to try Mark Osterman's recipe as outlined on your site for my first go . . . My goal is to have plates in the camera by the Easter weekend!

Thanks again!

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

dwross said:

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

Click to expand...

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

Adam's Dad

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?

Click to expand...

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!

Photo Engineer said:

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

Click to expand...

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

Kami-the-Trout said:

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?

Click to expand...

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)

!!

You can almost see pieces of the puzzle start to move together on the table. A dozen people working for one year will produce far, far more information than one person working for many dozens of years. Gelatin is a huge part of the picture (Thank goodness there aren't a bunch of silver variables, too! God Bless silver nitrate.)

Back to Capt. Pizzighelli's observation: "while one sample of gelatine will stand digesting for fifteen minutes with ammonia at 70C, another will produce a foggy emulsion if a temperature of 50C be employed". It's not just a matter of temperature in isolation. One gelatin will likely be fine in one recipe and bad in another, even given the same temperature. And, even variations to a recipe; hrst's observation about fogging a sensitized emulsion is spot-on with things I've seen. This is why totalamateur's suggestion about sticking with one recipe in the beginning is such good advice, and why it's best to start on the low side of a particular recipe's temperature range. Having said that: if one recipe seems to fail consistently for you, there are enough very good, very simple published recipes now to try something different. Just because the big picture is complex, does in no way mean that making a basic emulsion is complex.

Does anyone know how to start a 'sticky' thread? I think we should start to make a list of specific observations of exact times and temperatures, exact brands of gelatin, etc, with illustrations. I have high hopes that some of the lab equipment geeks here (a term meant to be the highest accolade!) will invent any number and manner of meters, but in the meantime, just a plain old list of brand names and procedures will go a long way. Important information gets buried in a thread like this.
d

With regards to to good Captain, I think that's why it's a good idea to start with photograde, deactivated gelatin.

Try to keep the variables at a minimum. And buy sufficient supplies so that you get to know them before you run out.

Kirk