View Full Version : Panchromatic Emulsion
09-28-2008, 03:10 PM
Chrome alum is the preferred hardener for gelatin on glass regardless of preparation according to two experts, one of whom coated glass plates commercially.
Usually, you use either chrome alum or glyoxal at 10% in water, but remember that they both decompose over time. Also remember that glyoxal is nominally 40% in water so a 10% solution of that is actually 4%. I use the same liquid measure of either one, but they are both sensitive to other ingredients and I have had melts harden up instantly with both based on the pH and other ingredients present. And, due to the mix of ingredients and the expense, I was unable to identify the precise nature of the problem.
Maybe someday I'll revisit the issue, but for now, I know that Chrome Alum or Glyoxal at equal liquid measure at nominal 10% dilution works. There is more precise information on this in your class notes.
06-07-2009, 07:02 PM
[QUOTE= However, remember that Chlorophyll was the first red sensitizer. I have seen it done! It isn't good, but it works!
Hello PE, I have been looking at chlorophyll, both suspended in water and extracted with methanol, with some success. I have been adding it as the final adition to the batches, and mixing at 45C for about 1/2 hour. Is there a better place to add the chlorophyll than at the end?
06-07-2009, 07:09 PM
I have seen the sensitized emulsion, but have never worked with it. At our last lunch at GEH, Mark Osterman had about 100 ml of Chlorophyll sensitizer there to show us. Our next lunch is Tuesday. If I can go, I will ask him about it.
06-08-2009, 10:49 AM
Bill - did you buy some chlorophyll? Or did you extract it?
It should be easy to grind up some spinach and then leach it with acetone and filter. A little magnesium carbonate can stabilize solutions, but chlorophyll degrades with exposure to light and I think it should be stored in the freezer.
06-08-2009, 11:37 AM
Yes, I should have added that chlorophyll is not very stable once extracted and suffers if one overheats it during the sensitization process. It is reported to be very difficult to work with due to this stability problem.
There are some plants that yield "better" chlorophyll than others. This should be available in the literature, but I'll check if I can.
06-08-2009, 04:04 PM
Kirk and PE,
Thanks for your support. Kirk,at first I mistook your advice about spinach as pure sarcasm. But now I realize it is a valid suggestion. Why acetone and not methanol? I have found reffrences to extraction via methanol.
As to where I got my chlorophyll, I have used both an aquious suspension and a dry powder. Both were supplied as chlorophyll/copper compounds. In either case a methanol extraction, worked the best, as evidensed by shooting a color chart in daylight.
PE- I am going to give the SDA3057 a second try once I receive my new shipment of silver,later this week. I want to keep both methods going.
06-08-2009, 05:11 PM
Bill - my info on chlorophyll is from doing the Standard Methods test for chlorophyll. They filter the algae, grind the filter with the algae in a tissue grinder using 90% acetone with 10% water saturated with MgCO3 as the extraction fluid. Then we centrifuge to get rid of the tissue and filter residue, and then analyse it for the chlorophyll content. So that's where my thoughts come from.
06-08-2009, 05:20 PM
I would not use the form containing copper. It has potentials for side effects. Acetone may not be good either. The samples I saw, I was told, were extracted with Everclear.
06-09-2009, 12:02 AM
What effects would acetone have? I seem to remember that Bill can't get Everclear in California, but I can in Oregon. At least according to wikipedia, he can't get 190 proof Everclear, but he can get 151 proof. Interesting, you can't buy 190 proof Everclear in New York state as well!
06-09-2009, 02:07 PM
Well, at our lunch today, all agreed that acetone was not good as it can interact with gelatin and other emulsion ingredients.
Use either ethanol or methanol for extraction, and some suggest common Ivy as a good source for fresh chlorophyll. I am told that coating the plate first and then bathing in alcohol+chlorophyll is best.
I am supposed to get some references.
06-10-2009, 10:53 AM
Hi PE and Kirk,
Thanks for the info.
PE-It is interesting that soaking the coated plate in the dye solution works best here. I recall that you do not like this method for other dyes. Any idea as to concentration?
Kirk-You are correct in that Everclear is not sold in CA. But I have just ordered some ethanol and already have methanol. I have to go through 3rd parties to get the latter. Ethanol is availible from The Science Shop. Also I can purchase 70% ethanol from any drugstore. But it is purposely mixed with some poison to keep people from drinking it.
Agai, I have to wait for more silver befor I try this.
06-10-2009, 11:24 AM
Do NOT use denatured alcohol. The added chemistry forms a colloidal suspension when mixed with water (among other nasty things) and will harm the emulsion.
As for soaking the plate, this was done in early days to sensitize, but was time consuming and not very precise. The amount to use is quite debatable, and my friends could not even begin to suggest a starting point. The soaking would have to be by trial and error and then, how would you quantify it? This is an added difficult step, verifying the effectiveness of the sensitization step.
06-10-2009, 01:24 PM
All sorts of chemicals are added to ethanol to denature it. You can see in the Code of Federal Register all the approved formulas for doing that: http://www.access.gpo.gov/nara/cfr/waisidx_08/27cfr21_08.html
From methanol to gasoline to pyridine are used - and you generally can't tell what you have when you get denatured alcohol. If the label says "SD alcohol XX" where XX is a number, you can look up in the CFR link above to find out which additives were used.
On the chlorophyll, it sounds like they use the soaking method for sensitizing to minimze the degradation of the chlorophyll.
06-10-2009, 02:38 PM
PE and Kirk,
I will NOT use denatured alcohol. That is why I paid $13 for 1 pint of ethanol from The Science Shop. The 70% ehanol is sold as "rubing alcohol". So the added chemical is probably something of low toxicity, like IPA.
I will just wait untill the ethanol arrives, then try to find ivy in the desserts of southern CA. Maybe spinach is not a bad idea Kirk.
06-10-2009, 03:13 PM
Isopropyl is one of the denaturant used.
A bottle of chlorophyll powder I've seen said it was extracted from spinach. Here's a nice extraction method that should clean up your extract pretty well.
It uses acetone for the extraction, and then cleans extracts the extract by adding water and hexane. The water will mix with the acetone hold onto the acetone and other junk in the first extract, and the hexane will extract the chlorophyll from the water/acetone mix. You can then blow down/evaporate the hexane to get rid of it and make some powdered chlorophyll to use in whatever solvent you want.
06-12-2009, 02:46 PM
Cool. I will buy some hexane.
The ethyl alcohol I bought turned out to be 90% ethanol,5%methanol and 5% IPA. That annoyed me because it was advertised a "Reagent Ethanol". Probably OK for extracting chlorophyll. But I will try the procedure that Kirk suggested.
But I can do nil until my silver arrives.
06-12-2009, 02:48 PM
Bill - that mix for your ethanol should work pretty well for extraction. You could use it that way in the alcohol solution as a stock, or concentrate into hexane and then dry it.
06-12-2009, 02:50 PM
That particular mix of denaturants is acceptable. At least as long as it does not turn cloudy when mixed with water. That is the crucial point with some denaturants.
As for doing a pan emulsion, everyone I associate with here says don't until you have a good ortho emulsion and don't until you have good test methods set up to prove the sensitivity.
06-21-2009, 12:33 PM
Ok, here is an update on chlorophyll supplied courtesy of Mark Osterman.
In the Photographic News, 22 June, 1888, an early report is given that plates can be sensitized by chlorophyll. This work was by Ives and also by Abney. No methods are described, nor are results, merely that it has been achieved and was done by bathing the plates in alcoholic chlorophyll.
In the textbook "Collodion Emulsion" by H. O. Klein, he describes the same work with much more detail including wedge spectrograms. He calls chlorophyll remarkably unreliable but good when it works. One problem is that due to the spectrum of chlorophyll, it can cause up to 5 peaks of sensitivity in the emulsion, and can actually increase blue speed. In fact, the increase in blue speed must be taken into account in order that one fully recognize that any red speed has been achieved.
The stability of chlorophyll solutions is not commented on, but the implication is that it varies depending on source and on keeping conditions. One report says that the solution was stored over zinc powder to improve stability.
All refer to it being best used by bathing dry plates in a solution of chlorophyll and then redrying the plates before use. They also comment that the sensitized plates keep better than unsensitized plates. No data is given on that.
06-21-2009, 02:53 PM
I am not trusting my life to chlorophyll as a red sensitizer, but I do want to try it. I also need to RE-TRY SDA-3057. This time at your recommended higher concentration and temperature. I have not been able to try anything this past week because I have been low in AgNO3 and low on time. But I expect to give them both a try this week.
I am storing both the SDA 3057 and the SDE 8006 at 1% in methanol, in brown glass at a temperature close to 0 degrees C. The SDE 3008 comes partly out of solution , even when brought to room temperature. But warming to about 100 degrees F redisolves it.
Has that been your experience?