catechol storage problems

Leon · Jun 22, 2005

I have a store of dry chemical packs (small plastic press-lock-type bags. ) already weighed out to be mixed up as Pyrocat (done for me last year). I checked them today and found that the catechol seems to have "sweated" into a brown liquid - possibly through condensation forming, although I tried to prevent this by putting the bags inside other bags inside yet another bag then in a large tupperware type airproof box.

Can anyone tell me if the catechol would be ruined by this - it still smells very strong so hopefully not. I have a few years worth of dry developer mix stashed away in there

colrehogan · Jun 22, 2005

Is all the catechol stored in bags? It may be going bad on you (and you don't want to be smelling it a lot either). I worked with it at work a while back and ISTR that it came in an amber jar (from the manufacturer) sealed with wax around the lid to keep out the air.

Ian Grant · Jun 22, 2005

The Catechol has definately gone off and oxidised.

Unless relatively fresh when made up Pyrocatechol developers will cause overall staining.

Fresh dev is pale just a hint of straw colour, once it tends towards the colour of weak tea it's useless.

Ian

gainer · Jun 22, 2005

For future reference, you may want to store catechol that you are not going to use immediadetly as a 10% solution in propylene glycol. 10 ml of this solution, of course, will be 1 gram of cathechol, and if it is fresh when you make the solution, it will be fresh when you use it. This solution has other uses than Pyrocat HD, though that is certainly a good one.

In order to dissolve the catechol in the glycol, some heat must be applied. I think it can be done at about 150 F, which is not much above the recommended temperature for mixing developers like Dektol or D-76.

If you buy 100 grams of catechol and 1 liter of propylene glycol, you have a long lasting supply of solution.

Gerald Koch · Jun 22, 2005

The MSDS says that catechol is stable under ordinary conditions of use and storage. I find no mention of it being deliquescent. Storing the solid in plastic bags is not a good idea since it should be protected from exposure to air and polyethylene is permeable to gases including oxygen. Keep it (and other developing agents) in the original container and in a cool, dry and dark place.

Since the catchol has turned to a brown liguid, obviously there has been some oxidation. I would toss it. The guiding principle with chemicals is that they are cheap in relation to film.

Leon · Jun 22, 2005

thanks for your replies guys ... the person who sold it to me and mixed it for me (a well experienced producer of photochemical mixes and chemist) seemed to think it would be fine packaged like that indefinitely. I should have mixed it into solution straight away - bugger!

fhovie · Jun 22, 2005

I premake dry kits all the time - each chemical goes in a small food grade plastic bag (4 mil) and is heat sealed and then the collection of bags goes in a kit bag that is heat sealed. I have never had any chemicals go bad in this double heat sealed configuration. I have sealed both gallol and catechol this way as well.

Loose Gravel · Jun 22, 2005

'Plastic bags' constitutes a wide variety of materials, some of which don't keep out anything but the rain. I notice while reading the Bradley bag catalog that they advertise some plastics for food, some for hardware, some are oxygen barriers, etc.

Just food for thought.

Claire Senft · Jun 22, 2005

Take some of the residue that you have and make a small amount of Pyrocat. Shoot a strip of identical negatives. Cut your strip into two pieces and develop one each in your known good Pyrocat and your apparently oxidised material for the same time. You will soon know if your cathecol is ruined or not.

bogeyes · Jun 22, 2005

Just to make it clear I will ask, is that warm up say 600ml of glycol add the catchecol then top up to 1000ml with warm glycol or just warm up 1000ml of glycol and mix in 100g of catchecol?

Tom Hoskinson · Jun 22, 2005

What Jay (and Pat Gainer) said!

I've got a liter of catechol/glycol stock concentrate in my darkroom that is now a year old - still fully active, with no color change.

catechol storage problems

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