Mixing Pyrocat-HD In Glycol vs. Water

Solubility, but you could leave out the Bromide entirely, Sandy King has said this himself. Even at 2 gms once diluted 1+1 to 100 that's only 0.02g/litre not enough to have any effect.

Unless you want to keep Pyrocat for years on a shelf just mix in De-ionised or Distilled water, as long as the Metabisulphite is reasonably fresh it keeps 3 or 4 years even in a partially full bottle.

Ian
 
OK noted thanks. I'd not noticed the Bromide not being soluble, but the phenidone definitely stuggles to go into solution. I think it was someone here (you, perhaps) that recommended first dissolving the phenidone in a small amount of alcohol and then pouring that into the mix - which works splendidly.

I did find another place on the 'net where Sandy King is quoted to have said to reduce the bromide to 1g for both water- and glycol based stock.
 
Many years ago, I'd guess 2008, I contacted Sandy King as I planned to mix Pyrocat HD part A at double strength to take back to Turkey, we discussed the issue of dissolving the Metabisulphite and Bromide, if mixing in Glycol. He said he used just enough water to dissolve them. I mixed at twice the weights and took 3 500ml bottles with me, I still have one and it's still OK. I bought the Potassium Carbonate in Turkey,

When I needed to use the Part A I just diluted to back 1+1 with water to normal strength Part A. However since then Ive never bothered using Glycol again it adds significantly to the costs. I found that the Pyrocat HD (in water) that I'd left in my UK darkroom was keeping well, and in fact was still fine after 4 years. So it made no sense wasting money using Glycol.

Ian
 
I have found my Part A (apparently) deteriorating within a year. Glycol was an attempt to make this problem go away. However ... in digging into this more deeply, it may be that my Metabisulphite is way too old and thus not doing its job, and THAT may be why I am seeing deteriorating long term results. I did a bit of reading and it seems that Metabisulphite is good for only 3-4 years in original packaging. I think mine is more like 25 years old!

In any case, mixing in glycol isn't - in my view - particularly more difficult and should ensure better long term storage. At the dilutions I use for long semistand, 500ml of Part A probably will last me the better part of 18-24mo.
 
The key to longevity is using relatively fresh Metabisulphite. It's cheap and can be bought in any town.

Ian
 
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So, a further question if I may. I've just mixed up a batch in glycol with my elderlyMetabisulphite. In your judgment is the low oxidation behavior of the glycol sufficient to preserve the developer in the face of likely weakened Metabisulphite, or should I just redo the whole lot?
 
Just buy some fresh Metabisulphite, add the same weight again, the level is low and just forms Sulphite when mixed with Part B, or add 4g of Ascorbic acid. Neither will affect how the developer works but will help preserve the developer.

Ian
 
Home brew shops, Boots used to sell it, eBay is the best place, or Amazon. Most expensive is as Milton powder :D

Ian
 
Campden tablets are Sodium Metabisulphite but you should be able to buy powder as well.

Ian
 
I suppose the tablets will be ready-weighed. A small extra convenience.
 
Just to tie off the conversation I started here...

I've gone ahead and mixed my first batch of Pyrocat-HD in Propylene Glycol. I'm happy to report that it was no different, really, than mixing in water, other than the PG has to be heated to about 150F whereas water can be used when it's raised to only 130F or so. In either case, I have found that mixing the phenidone in 5-10ml of 91% isopropyl alcohol does wonders for its solubility and ability to go into solution.

I'm running my first negs through this developer. Assuming it works, I will likely stick with PG because - given that I dilute significantly more than nominally recommended - my volume of work is such that a single liter of Part A is likely to last me well into several years.
 
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