problem: grey image
Dear photo enthusiasts,
I am a new member of your forum with a 'big' problem. After many years of practice in a darkroom (this includes the use of FOMA emulsion) I've decided to mix the emulsion myself. I followed a very simple recipe:
Potassium bromide 16g
Distilled water 125ml
Silver nitrate 20g
Distilled water 125ml
Everything went well until I developed the first test print. It was going to be a simple photogram to find out how the coated paper works. Unfortunately, all I could get from that were edges of the object: the part of the image that was supposed to turn black came out as very mild grey.
I must add that I used 240 Bloom Pigskin Gelatin.
I went through many threads on this and different forums, but I couldn't find any place that mentions similar problem, or the very basic rules of emulsion making.
Is there anyone who has any idea what could have gone wrong during my process?
I apologize if this issue has been discussed already but I really couldn't find any information (simple enough) that could help.
Welcome to APUG and emulsion making!
Could you supply a little more information on how you made your recipe? It's likely that it's just a lot slower than you're used to. A couple of possible solutions are more exposure and/or more heat during the emulsion making. Maybe letting the emulsion sit for a bit in the heat before refrigeration. If you washed the emulsion before coating, you may have left too much water so that the emulsion is too dilute. Perhaps coated too thin (?) There are a couple of other possible things to try, but these here a good start.
Best of luck,
thank you for your reply. I was wondering about the temperature myself; I am not really able to control it very much: I boiled water in a kettle and used it as water jacket. I have a digital thermometer. but I don't have any special device that would keep the water at stable temperature.
Anyway, I was unable to find any info on how the temperature affects the quality of the final product.
After the emulsion was mixed I immediately filtered it through cotton in a funnel and then I coated it straight on the paper; 1 layer only. I used plain wall paper which I always use with emulsion. I didn't wash the emulsion (don't really know how to do it and whether it is necessary).
I am sorry I must sound really dumb
Regarding to the longer exposure: I left a test strip on a direct light for about 30 minutes and I only got the same grey. It kind of looked like an unexposed, but fogged paper.
Thank you for any suggestion.
I would suggest that you purchase The Silver Gelatine book written by Martin Reed from Silverprint:
It is truly 'THE Bible' if you want to experiment with this area of photography.
Welcome to APUG .
I think you need to coat paper two times: once, let it dry, and then again. Try and let us know is it helping.
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OK, that drills it down a bit. If you coated emulsion when it was very hot, it's likely your coating is far too thin. Let it cool to around 35-40C before you coat.
It's not absolutely necessary to understand what's going on to make a perfectly good emulsion. You can just experiment until you get the results you like and then repeat each time. But, if you'd like a little more info, I can suggest The Light Farm. The best place for you to start would be here: http://www.thelightfarm.com/cgi-bin/...tent=06Jan2013
Last edited by dwross; 01-13-2014 at 09:59 AM. Click to view previous post history.
Reason: wrong link!
Oops and apology. Posted the wrong link for you. (Still had it cached from an email I just wrote.) Try this:
Thank you very much guys. Your help is much appreciated!
David: I have the book but it is still bit too difficult to understand; probably for its vast amount of information.
Darko: I've read about that and I will definitely try several layers. Thank you.
Denise: That is an amazing site with all the info I require. I am sure I will learn a lot from it.
Thank you again
Having recently participated in some salt printing experiments at the George Eastman House, I can say the paper you use can have a MAJOR effect on the d-min of your prints. Not all acid-free 100% cotton fiber papers are equal. You will probably need to experiment to find the most suitable paper.
The temperature of boiling water is usually too high for emulsion making. It is 100 C and emulsions are made between 40 and 80C. So, this may be breaking down the gelatin and ruining the emulsion. Try using 50 or 60C and add the Silver Nitrate over about 2 minutes. This may increase contrast.
Also, leaving the emulsion unwashed leaves bromide in it and this is a restrainer. That can lower Dmax.
Last but not least, addition of a tiny amount of Iodide as KI in a 1% solution may help. Based on Silver weight use about 3% of the Iodide for every 160 g of Silver Nitrate.
In any event, this emulsion will be about 3 stops or more slower than a modern enlarging paper, so beware of this big speed difference.
If you need more help, you might try my book available either through the Formulary or Fotoimpex. Ads with URL redirection are here on APUG at the top and bottom of the screen on a rotating basis.
Best of luck.