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Fulvio
09-12-2008, 03:07 PM
I'm in the process of making an emulsion suitable for bromoil.

I did some attempt in the past with an unwashed emulsion recipe.

I'm trying now with a washed silver-bromide emulsion as described by Mark Osterman in the second edition of Christopher James book. The trick of doing bromoils is to create a matrix with a special bleach for a regular bw print. Since the bleach also hardens the emulsion while bleaching it, the emulsion itself shouldn't contain hardeners. At least this is my understanding.

In the past I used commercially available emulsions and only those without hardeners worked for making bromoils.

I made an emulsion without adding chrome alum in it. I still have to try it for bromoils. It prints fine in Neutol WA, but it is a little bit too weak (melts at room temperature). With two coatings of emulsion this problem becomes less apparent, but is there a way to make the gelatin more consistent without using chemical hardeners such as chrome alum?

Thank you

dwross
09-12-2008, 05:23 PM
Hi Fulvio,

I would love for you to try my latest negative emulsion with your bromoils. It is a washed, unhardened bromide formula. I use it to coat dry plates and it seems very durable. I wish I could link you to the recipe on The Light Farm, but I've had a terrible case of 'It's Summer!' for the last month and haven't gotten it posted yet. If you'd like to give it a try, pm me for my email address and I'll send it to you. If you're not in a hurry, it will available online within the month.

Best of luck,
Denise

Fulvio
09-12-2008, 06:34 PM
it's autumn :) you have a pm

Kirk Keyes
09-12-2008, 07:12 PM
It's finally summer, here in Oregon. September is always a beautiful month.

Photo Engineer
09-14-2008, 06:57 PM
The Osterman emulsion coats just fine onto paper as long as the process temperature is kept at or below 68 deg F. It gives good contrast in my experience.

It might be the developer or fix, or even the paper support you are using.

PE

Fulvio
09-16-2008, 07:40 AM
Yes temperature might have been a problem... I used this formula while it was quite warm in here (25-30C, that is above 68F)... Now that it dropped to 20-25C things are getting better. I actually played a little bit with the emulsion suggested by Osterman.... Perhaps my first batches were too thin. I had to triple coat to get successful results. With the new batch and lower ambient temperature with two coats it's just fine and acceptable, but haven't tried it with bromoil yet. It's quite slow (I haven't rated it, but I assure you it's very very slow)... I wonder for how long it will keep in the fridge. I added a little thymol as preservative. No chrome alum for the reasons I mentioned. When I need it, I scrap the necessary quantity and melt just that. So far I always prepared small batches (100-250 cc) because I'm afraid that making larger ones (500-1000) won't last enough before I use it all for prints. How long do you think it would keep?

Photo Engineer
09-16-2008, 08:45 AM
It should keep for about 1 month in a refrigerator at about 3 - 5 deg C.

PE

Fulvio
09-16-2008, 08:57 AM
that's great... But is there a way to extend considerably the shelf life of an emulsion? or do you know any formula for a home-made emulsion that lasts a very long time?

Photo Engineer
09-16-2008, 09:34 AM
Gelatin is a common culture medium for growing bacteria and mold samples. Silver metal is itself an antisceptic. These two balance out to allow an emulsion to keep for at least 1 month, but I've been lucky sometimes and have gotten 6 months out of an emulsion. The natural trend is to decomposition of the gelatin by 'bugs'.

Using rubber gloves and not breathing into your emulsion are good starts. We observed that if an emulsion was handled carelessly, it went bad faster. Dirty hands, breathing, sneezing etc. were definite problems.

Otherwise, nature takes its course. Sorry.

PE

Fulvio
09-16-2008, 09:41 AM
I undestand. However I've observed that commercial made emulsions keep longer than 6 months. I've been using a FOMA for months (almost 12) and its still good...

Photo Engineer
09-16-2008, 10:15 AM
Yes, and they probably use phenol or something similarly toxic. They also use stabilzers in the emulsion that prevent fog and speed changes. The Osterman emulsion uses none of these. It is intended for immediate use.

For more information, look at the full formula posted by Jim Browning here and on his web site. There you see the list of stabilzers including Sodium Azide which is one of them and as a solid is explosive!

Even so, I have gotten 6 months out of my emulsions.

PE

dwross
09-16-2008, 11:11 AM
Hi Fulvio,

There is an additional aspect to this that you might consider. I think that it is counterproductive to make a big batch that lasts months. It is my strongly held opinion that you should be making small batches that won't need preservatives and that you should be making them often. Big batches might be OK if you had years and years of experience making emulsions so that the technical details and tactile memory would be there for you even after months had passed.

But, for most of us, practice makes perfect. It really is trivial to make a batch of emulsion, and the more times you do it, the easier and faster it gets. And, the quality improves. I don't think you'll ever become proficient making emulsions if you only give it a go twice a year.

Denise

Photo Engineer
09-16-2008, 11:13 AM
Denise;

I could not have said it better. You nailed it. You see, I can make big batches with no problem as I have become used to it. Small batches are best, especially for starting out.

Thanks.

PE