Prescysol and Pyrocat-HD, actually the same -- any conclusions?

Going through some of the past posts discussing Prescysol and Prescysol EF, there is a supposition by some that they must be nearly identical to Pyrocat-HD. Has anyone come to any recent conclusions regarding this? Are the results seemingly the same? Where might any differences in their formulas lie? Are there any advantages to one over the other? Storage longevity, handling, agitation, film types, etc?

Is it Prescysol or Prescysol EF that most closely matches Pyrocat-HD? Any thoughts on what might be the difference in composition between the original and "EF" versions of Prescysol?

I've also notice that the Photographers Formulary now sells Pyrocat-HD "in Glycol", and says that this gives Pyrocat-HD a longer shelf life. Is this the only difference? Thanks.

Lotus M50 said:

Going through some of the past posts discussing Prescysol and Prescysol EF, there is a supposition by some that they must be nearly identical to Pyrocat-HD. Has anyone come to any recent conclusions regarding this? Are the results seemingly the same? Where might any differences in their formulas lie? Are there any advantages to one over the other? Storage longevity, handling, agitation, film types, etc?

Is it Prescysol or Prescysol EF that most closely matches Pyrocat-HD? Any thoughts on what might be the difference in composition between the original and "EF" versions of Prescysol?

I've also notice that the Photographers Formulary now sells Pyrocat-HD "in Glycol", and says that this gives Pyrocat-HD a longer shelf life. Is this the only difference? Thanks.

Click to expand...

You wrote: I've also notice that the Photographers Formulary now sells Pyrocat-HD "in Glycol", and says that this gives Pyrocat-HD a longer shelf life. Is this the only difference?

Based on the comparitive testing that I've done between Pyrocat-HD mixed in water and Pyrocat-HD mixed in Propylene Glycol, the only difference is shelf life.

Regarding your other questions, I have no experience with Prescysol or Prescysol EF, and their recipes are not in the public domain (unlike Pyrocat-HD, Pyrocat P and Pyrocat-MC).

I cant say they are Exactly the same but they are close. When I pour out the Pyrocat-HD from my tank after the time is up it looks pretty clear. Prescysol and Prescysol EF have a much darker color. That is all I can see that might say they are different. If I remember correctly the color of both was about the same before they were used to develop film. I think they use catchecol but I dont have any info on the formula.

lee\c

Quite a time gap had elapsed between using the Prescysol and becoming a steady PyroCat user. I pulled out some Prescysol negatives just now and did some comparing... They really are very similar in general tonality, highlight control and shadow detail. The grain is very similar, too. The Prescysol was the last commercial product I used prior to going into the home-mixed from components phase that I am still in. The Prescysol uses what appears to be a sodium carbonate based B solution. I recall my first PyroCat trials being with this alternative B solution, too. I tried the Prescysol following WD2D+ trials and recall the Prescysol giving denser, meatier negatives that were more what I was accustomed to with traditional developers such FG-7, DD-X or D-76. I recall being instantly comfortable with my printing from them and PyroCat negatives seem the same way for me and I find I'm doing a lot less burning and dodging and that many negatives require no manipulation in controlled lighting situations.

When I was ready for more Prescysol, it had reached the cold season in northern Wisconsin when I don't have very good luck shipping liquid items and this was when I was first re-energizing my return to the darkroom with homebrew and home-mix items. I certainly would whole-heartedly endorse anyone trying either of these (Prescysol, especially semi-stand and any of the PyroCat variants, as I've tried them all and had great results with all of them). During this same general testing period, I was trying some of Jay de Fehr's Pyro 510, HyperCat and other variations he was working on. They had good potential with great grain control, good mid-tones, decent highlight printing but I struggled to get shadow detail that I was happy with. I've meant to get back to some tweaking of them and never seem to get the time but there is also some potential there, I believe. The variations of PyroCat alone should keep me busy for some time! I needed to back off on agitation and time more than I expected to get the MC looking the way I like but that may become a new favorite, I'm sure!

Yes, my understanding is that they are both catchecol developers with strong similarities in dilution and use. This has lead to supposition by a few people that they may be nearly the same. As they say, however, the devil is in the details -- or in this case, does the possible small differences lead to differences in results with different films. I'll probably pick-up some Prescysol EF and try it with roll film.

craigclu said:

I tried the Prescysol following WD2D+ trials and recall the Prescysol giving denser, meatier negatives that were more what I was accustomed to with traditional developers such FG-7, DD-X or D-76.

Click to expand...

I had tried WD2D+ with roll film in the past (primarily Delta 100 and Delta 400) and I found the negatives a little thin. I'm ready to give Prescysol and/or Pyrocat-HD a try, particularly if they will produce a somewhat denser negative.

Weren't Prescysol and PyroCat-HD developed by different people. If so, it would be truly amazing if they were the same. As far as comparing negatives and saying that they were produced by the same developer that simply can't be done.

They aren't the same. The stain is a different color ( at least with ef). The development times are totally different.

Does prescysol have some of the same chemicals in it as pyrocat? Probably, but then so do most developers.

Best,

Will

Gerald Koch said:

Weren't Prescysol and PyroCat-HD developed by different people. If so, it would be truly amazing if they were the same. As far as comparing negatives and saying that they were produced by the same developer that simply can't be done.

Click to expand...

Maybe not so amazing, Gerald.

APug's Sandy King created and extensively tested Pyrocat-HD and published the formula and the test results in the open literature.

After the Pyrocat-HD formula and test results were published; Prescysol, etc. appeared on the market as proprietary developers that claimed attributes similar to those of Pyrocat-HD.

Will S said:

They aren't the same. The stain is a different color ( at least with ef). The development times are totally different.

Does prescysol have some of the same chemicals in it as pyrocat? Probably, but then so do most developers.

Best,

Will

Click to expand...

Will, What color is the Precysol stain and how did you determine the stain color? Do you have sensitometry and densitometry data?

Will S said:

They aren't the same. The stain is a different color ( at least with ef). The development times are totally different.

Click to expand...

As far as I know from reading product information on PeterHogan's website , and product instruction sheets from Photographers Formulary on Pyrocat-HD both Prescysol and Pyrocat-HD produce a brown stain. Further, for a number of films recommended development times are not significantly different. The notable difference with Prescysol is the claim that all films can be developed with the same development times.

Judging from the published dilutions, it may be that Pyrocat uses Potassium Carbonate and Prescysol uses Sodium Carbonate.

One can obtain 100 ml of B solution with 100 gm or Potassium carbonate whereas the typical mixture of B using Sodium Carbonate (100gm) is 500 ml. The typical use solutions are 1-1-100 with Pyrocat while they would be 1-5-100 with the Sodium Carbonate mixture. I use the Sodium Carbonate in my Pyrocat since the two sources of alkali are interchangeable for this purpose.

I have never used Prescysol so I have no other information or personal experience to draw from.

Lotus M50 said:

...The notable difference with Prescysol is the claim that all films can be developed with the same development times.

Click to expand...

I'd like to see some well controlled Sensitometry and Densitometry test data that supports that claim.

Tom Hoskinson said:

I'd like to see some well controlled Sensitometry and Densitometry test data that supports that claim.

Click to expand...

I'd be happy with just some anecdotal information from users' experience in trying to develop different film at the same time with Prescysol -- but Sensitometry and Densitometry testing would certainly go a considerable distance in attempting proving the claim. So far, however, I haven't seen much evidence of any type to support the claim.

Tom Hoskinson said:

Will, What color is the Precysol stain and how did you determine the stain color? Do you have sensitometry and densitometry data?

Click to expand...

I don't see much stain using my eyeball on pyrocat-hd negs (which I think is usual from what other people have written about it). I see a lot of stain (brown) on the prescysol-ef negs. They negatives do not look the same (to me), though I get excellent results (to me) printing with both. I have developed J&C 100, TriX and Efke 100 (all 120) and Tmax in 35mm in both developers. I use 10.5' semi-stand for Prescysol with all of these films. The times are quite different for pyrocat-hd (also semi-stand).

I'll just say that I am not a photographic scientist and I don't want to get into any arguments with anyone where the word "densitometry" is even mentioned, so I'll just bow out of this whole discussion now. I would be surprised to see someone determine that pyrocat-hd and prescysol are the same formula though. I wouldn't doubt that they are probably similar in some ways as they smell the same and the B solutions seem to weigh the same compared to the A

Thanks,

Will

Lotus M50 said:

I'd be happy with just some anecdotal information from users' experience in trying to develop different film at the same time with Prescysol -- but Sensitometry and Densitometry testing would certainly go a considerable distance in attempting proving the claim. So far, however, I haven't seen much evidence of any type to support the claim.

Click to expand...

I've developed rolls of Tmax 100 and TriX in the same tank at 10.5' semi-stand. They both printed on VC paper easily. Beyond that, I can't say. I like prescysol and I like pyrocat-hd. I also like Rodinal....

Thanks,

Will

Lotus M50 said:

I'd be happy with just some anecdotal information from users' experience in trying to develop different film at the same time with Prescysol -- but Sensitometry and Densitometry testing would certainly go a considerable distance in attempting proving the claim. So far, however, I haven't seen much evidence of any type to support the claim.

Click to expand...

Well, in my estimation there is just not much reason for anyone to go to that kind of trouble. In order to make a real valid comparison one would have to run run tests with the same dilution, agitation and film to establish family curves for both Visual, Blue and UV readings, and see how they compare. But what would be the point? Better to just speculate and hold on to some of the mystery of life.

However, if anyone is interested it should be possible to get data sheets from PF showing what the two formulas actually. They would not tell you they were exactly alike however, because in formulas the actual ratio of the chemicals can make a very big difference.

Sandy

Donald Miller said:

Judging from the published dilutions, it may be that Pyrocat uses Potassium Carbonate and Prescysol uses Sodium Carbonate.

One can obtain 100 ml of B solution with 100 gm or Potassium carbonate whereas the typical mixture of B using Sodium Carbonate (100gm) is 500 ml. The typical use solutions are 1-1-100 with Pyrocat while they would be 1-5-100 with the Sodium Carbonate mixture. I use the Sodium Carbonate in my Pyrocat since the two sources of alkali are interchangeable for this purpose.

I have never used Prescysol so I have no other information or personal experience to draw from.

Click to expand...

Don,

That is a good observation, and I would bet dollars to dimes that this is indeed the case. And, as you remark, the use of either sodium or potassium carbonate in Pyrocat-HD is interchangeable at about a 75% stock solution of PC, used 1:1:100, or a 20% solution of sodium carbonate, used 1:5:100. In other words, you get the same results with both sodium and potassium carbonate, provided that you adjust for the percentage of the stock solution.

I prefer potassium carbonate because of the simplicity of the symmetry in ratio of the amount of Stock A and B needed in the working formula, but of course, there is nothing sacred about that either as it is sometimes desirable to use a higher ratio of Stock A.

Sandy

Donald Miller said:

Judging from the published dilutions, it may be that Pyrocat uses Potassium Carbonate and Prescysol uses Sodium Carbonate.

One can obtain 100 ml of B solution with 100 gm or Potassium carbonate whereas the typical mixture of B using Sodium Carbonate (100gm) is 500 ml. The typical use solutions are 1-1-100 with Pyrocat while they would be 1-5-100 with the Sodium Carbonate mixture. I use the Sodium Carbonate in my Pyrocat since the two sources of alkali are interchangeable for this purpose.

Click to expand...

This is interesting because while Prescysol is 1:5:100, Prescysol-EF is 1:1:100.

Lotus M50 said:

This is interesting because while Prescysol is 1:5:100, Prescysol-EF is 1:1:100.

Click to expand...

That suggsts to me that the B solution of Prescysol-EF is potassium carbonate. If the -EF version is in fact finer grain than the original Prescysol this would not explain the finer grain since, as Don mentioned earlier, sodium and potassium carbonte give identical results when the actual amount by weight of each is equalized in the working solution.

There would be several options for modifying Prescysol to give finer grain. In the case of a pyrocatechin + phenidone staining developer, just reducing the ratio of phenidone to pyrocatechin in the formula would give more stain, and thus more grain masking, but probably less EFS. So, if anyone has compared Prescysol to Prescysol-EF with the same film and type of agiation, was there more stain with -EF?

Thing is, there is usually something of a trade-off between grain and acutance, so another question, assuming anyone had made the above comparison, was there a difference in apparent sharpness?

Sandy

sanking said:

There would be several options for modifying Prescysol to give finer grain. In the case of a pyrocatechin + phenidone staining developer, just reducing the ratio of phenidone to pyrocatechin in the formula would give more stain, and thus more grain masking, but probably less EFS. So, if anyone has compared Prescysol to Prescysol-EF with the same film and type of agiation, was there more stain with -EF?

Thing is, there is usually something of a trade-off between grain and acutance, so another question, assuming anyone had made the above comparison, was there a difference in apparent sharpness?

Click to expand...

These are the relevant questions and I wonder if anyone who has used both Prescysol and Prescysol-EF could share their experience in this area? They are not addressed in any Prescysol product information which seem to suggest that the only difference is finer grain with Prescysol-EF (if so, is there any reason at all to use the original Prescysol or are there, in fact other differences?)

I am hoping that Peter Hogan, a member of the forum and the developer of Prescysol and Prescysol-EF, will eventually contribute to this discussion and clarify some of these issues for users and help give us greater understanding and comfort in selecting his products.

As I understand it Prescysol-EF is designed to achieve the best performance from 35mm negatives, whilst Prescysol is designed for medium format and larger. As far as I can tell they achieve that aim very well indeed.

Dave Miller said:

As I understand it Prescysol-EF is designed to achieve the best performance from 35mm negatives, whilst Prescysol is designed for medium format and larger. As far as I can tell they achieve that aim very well indeed.

Click to expand...

So what would happen if you used Prescysol-EF for medium format? How would original Prescysol be better? I can see that the claim of finer grain would be advantageous for 35mm. However, it would clearly also be advantageous for medium format. That is, unless you have to give something up that you rather have for MF to get the finer grain. What would you be giving up from original Prescysol by using Prescysol-EF to get the finer grain?

Lotus,

love the avatar I will be voting for the Kinkster myownself. WRT to prescysol and Prescysol-EF I cant say what the difference is. Don Miller thinks regular Prescysol uses Sodium Carbonate for part B and EF probably uses pot carbonate. I dont think it makes a dimes worth of difference what format you use with either formula. I suspect it it hype. Can't prove it but that is what I suspect.

lee\c

I use prescysol-ef on 120. It produces negatives which I can print from, so I'm guessing it works. (There is more visible stain than prescysol too it seems to me btw)


Best,

Will