Has MY PyrocatHD (A) Died ?

I agree Ian G probably knows far more than most but I was just informing others of my experience with the WPS Pyrocatchetol. Shame you have discarded the other 500ml it may have worked?
 
As Ian B alluded to earlier I also have some of the same 'orange' Pyrocat as him but when I saw conflicting opinions I decided to pop outside last night and do a quick exposure on Fomapan 100 film. I developed the film this morning in my 'orange' Pyrocat for 12 minutes and after a fix and wash I was delighted to see this 'proper' image: :)

Orange_Pyro_Test2.jpg

Please excuse the slapdash presentation but it serves it's purpose. :confused::D
 
To be on the safe side I have also decanted mine into glass bottles to hopefully prevent any further 'enhancements' ;) The only explanation for the colour change I can offer is that something in the Pyrocat formulation has reacted with the particular bottles used by Wet Plate Supplies. It is known that all plastics leech out chemicals, some more than others, so is it possible that these bottles leeched out some of their colour? Whatever the reason it doesn't seem to have caused the affected developer any discernable activity problems. It would be a shame to ignore this source of affordable Pyrocat so perhaps it would be wise to decant any further purchase of Pyrocat developer into glass bottles - just a thought.
 
I saw the bottle Ian brought with him yesterday, the black plastic bottle Pt A was in should be fine.

Pyrocat HD Part A won't dissolve in just Glycol so there has to be a little water as well. Pyrocatechin will oxidise very quickly in solution so Sodium Metabisulphitewhich is a powerful anti-oxidant is added in Part A, to prevent this, it works very effectively. However Metabisulphite itself breaks down with time to plain Sulphite, how fast depends on the freshness of the Metabisulphite and the type of bottle used for storage.

Pyrocat Pt A keeps well in just water, I'm just using old Rodinal or Ilford PQ developer bottles. There's two possibilities why this Pyrocat has begun to oxidise, either the Pyrocatechin or the Metabisulphite wasn't particularly fresh, the colour change indicates it's beginning to oxidise. the problem is once it starts it begins to collapse rapidy.

At what point the oxidation becomes a serious issue would be hard to pinpoint. The problem is that you get uneven background staining, I see this with Ilford IT-8 toner which uses a simple Pyrocatechin re-developer which oxidises in about 5 minutes and if not fresh stains the paper base, I now use Pyrocat HD as the re-developer.

Ian
 
I doubt that mixing in either distilled water or glycol would have any affect on the outcome of color. I suspect the reason might lay with different manufacturers of the Catechol and/or different quality of this chemical. It could be age, etc, of the metabisulfite, too. Interesting, though...over many, many years of mixing it myself, my A has always been clear to slightly straw color.
 
Alan, it's a change in the colour and is purely due to oxidation.

Ian
 
Oxidation alone won't explain the distinct difference between suppliers. Oxidation would affect all samples the same way. There must be some other factor. An undeclared ingredient, perhaps? It seems improbable that the users are divided into two camps.
If the orange stuff works as expected, then this is mere curiosity, of course.

Keith,
You are quite right. The Silverprint bottles seem very expensive. I looked at the Baldwin's site and found that they make dispensing pumps to fit their bottles. They dispense 2ml. Would that be worth considering?

https://www.baldwins.co.uk/black-plastic-pump-top-for-plastic-and-syrup-bottles
 
David M said:
......Keith, You are quite right. The Silverprint bottles seem very expensive. I looked at the Baldwin's site and found that they make dispensing pumps to fit their bottles. They dispense 2ml. Would that be worth considering?

https://www.baldwins.co.uk/black-plastic-pump-top-for-plastic-and-syrup-bottles
Click to expand...

I'm not sure I would trust their accuracy David but, apart from that, wouldn't leaving traces of developer in the nozzle pose a risk to conntaminating the next 'shot'? Personally I use either 10ml glass syringes or tall and thin 10ml graduates for measuring out what I need, both easily cleaned. :)
 
I did wonder about residue. A quick rinse under the tap perhaps? Repeatability is certainly a bigger worry. I mentioned it because it seemed interesting, not because I can personally recommend it. Might be useful for non-critical dispensing, like stop or wetting agent.
Some developers apparently thrive on a little bit of used solution, but I have no experience of this. Others may know. Keeping it simple is more than enough for me.
 
Ian Grant said:
Alan, it's a change in the colour and is purely due to oxidation.

Ian
Click to expand...

OK. In my experience, the only change in color that I've ever witnessed is straw (fresh) --> dark straw (still good) --> nearly brown (questionable at this point; I wouldn't use it) --> dark brown (dead).

I've read on other forums that folks mixing fresh batches have a red color like Ian's example on the right. Of course, this could still be explained away by oxidation because we don't know the nature of the water used, mixing technique, etc.
 
So, we are saying that one supplier consistently stores their ingredients in an unsuitable way?
 
David M said:
So, we are saying that one supplier consistently stores their ingredients in an unsuitable way?
Click to expand...

Maybe not intentionally. If it was the Metabisulphite that was not at its best when used, would there be any way of knowing that from it's Raw state.
 
Ian, just a thought... Do you have some sodium bisulfite around? If I remember correctly, you're mixing Pyrocat-HD in water? Sodium bisulfite becomes sodium metabisulfite when it hits water. Might be interesting to mix a small amount of Part A, using sodium bisulfite, and see what color you get.
 
Alan, Sodium Bisulphite doesn't form Metabisulphite when dissolved.

Pure Sodium Bisulphite is unstable and quite expensive. JT Baker sell both and the MSDS sheets differ, what's sold commercially as Bisulphite (not analytical reagent grade) is a mixture of 58%-99% Sodium Bisulphite and 42%-1% Sodium Metabisulphite.

Sodium Metabisulphite is >=97% Metabisulphite and is a much more powerful anti oxidant. What's important is the free SO2 associated with the Metabisulphite, this forms weak Sulphurous acid in solution that protects the developing agents from oxidation.

As the SO2 dissipates through the wall of a low grade plastic bottle the Mrtabisulphite becomes Bisulphite which is unstable without the presence of a little Metabisulphite/SO2, with no SO2 the Bisulphite begins to break down and become Sulphite.

Ian
 
You must log in or register to reply here.
Back
Top