Glycol and fog
This is the first time I experiment with a homebrew developer. I tried Pat Gainers PC-Glycol developer. I heated the ethylene glycol (antifreeze) and dissolved 100 gr of Ascorbic Acid and 2.5 gr of Phenidone A.
I exposed delta 100 and HP5+ from zone 0 to zone XI with a Nikon F4, and tested at 1+50 for 3, 6, 9, 12 and 18 minutes.
When measuring densities I zeroed on B+F. To my astonishment the exposed frames from zone 0 to III had uniform densities above B+F af about 0.4. Only after zone III the curves begin to rise.
I cannot explain this behaviour. Is it just fog? Then why don't I see it at unexposed parts of the film? And this way film sensibility would be minus 2 stops for both films. Is that normal?
Can anybody explain this to me?
I don't have any experience with ethylene glycol but some of my experiments with ascorbic acid and phenidone in glycol suggest that if the mixing temperature is to high when you add the phenidone, say over about 250 degrees F, there is an increase in fog. I have not tested this enough to be absolutely sure that the premise is correct but adding the phenidone when the solution is at about 150 degrees F solved the fog problem for me.
Originally Posted by argentic
However, with the ascorbic acid + phenidone developers I have found it necessary to add a little restrainer to get fog levels down to what for me are acceptable levels. With Pat's PC-TEA formula, for example, using 9g of ascorbic acid and .25g of phenidione per 100ml of propylene glycol, I also add 0.2g of bromide. Using FP4+ as an example, the addition of bromide drops the B+f value from about 0.20 to around 0.10. This vaue is still higher than the B+f value of 0.06 that I get with ABC, PMK and Pyrocat-HD but it does not present any particular inconvenience in printing.
Last edited by sanking; 08-13-2004 at 11:37 AM. Click to view previous post history.
jdef makes a good point: What alkali bath (if any) are you using?
Phenidone and Ascorbic Acid will dissolve in ethylene glycol (with continuous stirring) at fairly low temperatures - in the range of 70F to 150F. When I mix with any of the glycols, I start mixing at room temperature and add heat only if needed - and then only enough to get the chemical(s) into solution.
Hope that Pat Gainer will contribute from his experience with these developers.
Everything is analog - even digital :D
One additional point, my experience with Gainer's PC-TEA formulation with Kodak TMY 400 is Base + Fog of 0.14. See densitometry data below:
Developed 9.5 min. @ 70 F with gentle agitation: 10 sec/minute
Frame # Visual Channel
Everything is analog - even digital :D
When you use ethylene or propylene glycol or glycerine as solvent you must add alkali to the working solution. There are many possibilities. You don't say which, if any, you used. I never did try antifreeze without alkali. Perhaps some of the stuff that makes it green is alkaline enough to give some development.
You zeroed your densitometer on B+F, so the Zones that measured 0.4 surely can't be fog. They can oly be a mystery! Try using 1 tsp each of sodium carbonate and borax in a liter of water to dilute your glycol solution 1+50 for a quick and dirty test. This should give you a fairly linear plot from zones 2 on up with development of about 8 minutes at 70 F. If actual fog is too high for you, add some bromide to the working solution. I am not overly concerned about the fog I have seen, but if you use some of the alternative processes as Sandy does, double fog density means doubling an already very long exposure to UV light.
Keep in touch.
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You're right. I forgot to mention that I used a 0.5 % sodium carbonate solution to dilute the PC-Glycol stock solution, just like Pat says.
Originally Posted by jdef
I dissolved at 45 - 50 C which should be about 140 F.
Originally Posted by sanking
I used a 0.5 % sodium Carbonate solution.
Originally Posted by gainer
That's why I asked. I don't understand it either. If it's my Nikon F4 exposing for more than zone 0, I don't understand why this base density stays the same from zone 0 to zone III. And that on several different films. I will try another brand of ethylene glycol too. Maybe in this one there are additives influencing film development.
You zeroed your densitometer on B+F, so the Zones that measured 0.4 surely can't be fog. They can oly be a mystery!
I'm not overly concerned about fog either. But I don't like the curve to start rising only at zone III or even more. An EI of two stops less is a PITA.
Try using 1 tsp each of sodium carbonate and borax in a liter of water to dilute your glycol solution 1+50 for a quick and dirty test. This should give you a fairly linear plot from zones 2 on up with development of about 8 minutes at 70 F. If actual fog is too high for you, add some bromide to the working solution. I am not overly concerned about the fog I have seen, but if you use some of the alternative processes as Sandy does, double fog density means doubling an already very long exposure to UV light.
I guess I'm going to test the whole thing again with another camera, another brand of antifreeze, and bromide (one change at a time ofcourse). Restrictions on selling chemicals are very strickt here in Holland, so I cannot easily get chemical grade glycol or TEA. (I'm still looking for the Oil of Olaz variety of TEA )
I don't understand some of those restrictions, and I am sure you do not either. Propylene glycol is used in medicines, foods and cosmetics. It is also used by some dairy farmers and might be available from a supplier of such things. If you can get glycerine, it will do as well but is quite viscous.
Are you using shutter speeds to set the exposures for the various zones? If so, it might be a good idea to test the shutter for accuracy at the slower speeds. Of course, if that is the problem, it should show with other developers as well.