Pyrocat, Metol and Metabisulphite instead of Sulfite preventing oxidation

[pkr1979]

Hi all,

When mixing up Pyrocat M it is pecified in this thread that Metol should be the first ingridient: https://www.photrio.com/forum/threads/pyrocat-p-pyrocat-m.16994/

However, when mixing up D-23 (https://www.iconpublications.com/photon/july95/d23.html) its adviced to add some sulfite first, then metol... as the sulfite retards the initial oxidation of metol.

How is this dealt with when mixing up Pyrocat M... is it simply ignored or will Metabisulphite serve the same purpose as sulfite (a pinch of Metabisulphite first, then Metol, then rest of the Metbisulphite)?

Also, Ive seen a few variations of the Pyrocat M when it comes to Potassium Bromide... some includes it, some is replaced with Potassium Iodide, and some has none... Why apply it or not? Ive also seen different variations of the Potassium Carbonate solution (Part B) vary from 750g to a 1000g and wonder why... is this amount dependent on the content of the Part A solution?

Cheers
Peter

 

[koraks]

I don't think the rapid oxidation of metol when mixing a developer is a significant issue. If it happens, it's not going to make a noticeable difference in the activity of the final product. Btw, in my experience, this immediate oxidation doesn't necessarily happen when dissolving metol. It's usually barely or even not at all visible. I wouldn't worry much about it, really.

Also, Ive seen a few variations of the Pyrocat M when it comes to Potassium Bromide... some includes it, some is replaced with Potassium Iodide, and some has none... Why apply it or not?

I think Sandy King has always been quite clear on the thought that addition of bromide isn't really necessary with modern films. Perhaps if you use a lot of expired film, addition of a little bromide can help reduce fog somewhat, but again, it's not something to loose sleep over. Adding iodide seems somewhat risky due to the fact that a tiny amount can have a big effect on developer activity. I haven't read about adding iodide to pyrocat developers; surely it can be done, but I see no good reason to do so. If you really need to add a restainer, I'd stick with bromide or perhaps benzotriazole.

Ive also seen different variations of the Potassium Carbonate solution (Part B) vary from 750g to a 1000g

Again, I haven't seen this, but I'd just stick with the 75% ratio that is listed in the original formula. Increasing this will have some effect obviously on developer activity, but if that's intended, you might as well just increase the ratio of B to A when mixing the working solution. This is often done, especially when developing for alt. processes, by using ratios of e.g. 1+2+100 instead of 1+1+100 - which of course is a much more significant increase than increasing carbonate content of the B part by 33%. Frankly I don't see a good reason to increase the carbonate content of the B part, especially because it will make it more likely that the carbonate starts to drop out of solution. I've had the 75% B part on occasion crystallize out at the bottom, rendering it unusable because of the unverifiable concentration of the remaining liquid. In fact, if I were to modify the concentration of the B part, I'd rather decrease it to something like 37.5% and then use twice as much when mixing the working solution to prevent the B concentrate from throwing down solid carbonate when temperatures drop etc.

 

[pkr1979]

Thanks man - I'll keep this simple

 

[iakustov]

I don't use potassium bromide in solution A, my negatives print fine. However, I use 20% sodium carbonate as solution B and dilute 1+5+94 as described here.
What is not clear for me (and not only me) is why the dilution is not 1+3+100 which should be the correct amount based on molecular weight of both chemicals..

 

[destroya]

from experience, if you add the metol first then it will oxidize and you will be left with very a weak developer. I speak from experience, so let my mistake be a learning point for you -) . so now when I mix up my pyro-m, I put a pinch of sod sulfite before I put in the metol and I have never had issues since. but you are free to do what you want.

john

 

[john_s]

from experience, if you add the metol first then it will oxidize and you will be left with very a weak developer. I speak from experience, so let my mistake be a learning point for you -) . so now when I mix up my pyro-m, I put a pinch of sod sulfite before I put in the metol and I have never had issues since. but you are free to do what you want.

john

You could use a pinch of the metabisulphite that you have already got for the formula instead. You might as well do it even if someone says it's unnecessary.

Incidentally, there is a post here at APUG by Ian Grant in which he says that the metabisulphite needs to be fresh in order to preserve the Part_A, and that a little more would do no harm and might help. (This was with the Pyrocat_HD formula but would be the same situation with the metol vesion I expect).

 

[pkr1979]

Thanks guys,

I mixed the chemicals before seeing the latest posts, so I mixed the Metol withoud adding any sulfite or disuplfite first. I mixed at room temp and I think Metol is supposed to disolve better in room temp water then warm water... conntrary to other chemicals. I dont know that this is the case though. Anyway, I assume to figure out if it works as intended is to develop a film and see if it turns out as expected? I did check if a developer works with a film strip test but that doesnt say that much about the strength - I assume.

Also - I got both Potassium Bromide and Potassium Carbonate, so I used Potassium Carbonate at 750g/L.

Cheers
Peter

 

[iakustov]

I mixed the Metol withoud adding any sulfite or disuplfite first

I do the same and solution A I prepared 1.5 years ago is still good.

I think Metol is supposed to disolve better in room temp water then warm water

I can't give the exact figures for solubility, but all the formulas for metol-based developers I know suggest a warm water (around 50C) as it dissolves much better.