Shelf life of powders

[Snapper_uk]

I haven't done any home printing for a while, but I'm going to have a go this week. I've just found a few boxes Fomatol PW paper developer in the loft - expiry date is 2006 and it's been stored in less than ideal conditions. Is it worth giving it a go, I don't really want to waste my time using this if it's going to have gone off.

Also, how long to unopened bottles of liquid developer last for?

 

[Roger Hicks]

Powder developers are usually described ar having an 'indefinite' shelf life. I asked Ilford what they meant by this and they said, "A long time, but we don't know how long. If it were forever we'd say forever, but it doesn't usually go off in a hurry."

For liquid film developers, the answer is 'anything from a few months to several years, depending on the developer'. You can't rely on discoloration as some developing agents hydrolyze to colourless but inactive compounds.

Cheers,

R.

 

[sevo]

Except for some chemicals (e.g. liquid mix blixes and fixers) that self-destruct after a while, it is mostly a matter of the container failing.

Canned powder Kodak developers last until the can corrodes - i.e. forever if you store the can in a permanently dry place. And the same goes for liquid chemistry in glass bottles.

Modern packaging in plastic bags and bottles won't last quite as long until it leaks, and other, less easily observed/controlled environmental factors like UV or ozone can cause plastics to fail prematurely, so YMMV - but as long as the packages seem unharmed and colour and consistency of the contents are in the original state, they are probably still good. But as plastics can deteriorate so that they leak oxygen or some chemical while still water proof and solid, and as the chemicals might not change in appearance when affected by such a molecular leakage, there can be no definitive visual proof of integrity of chemicals in plastics containers.

 

[mwoenv]

I used to make 1 liter working solutions of Kodak Dektol paper developer and store the remaining powder in sealed double plastic bags. However, within a month the white powder would turn tan and then brown. I assumed the color change indicated oxidation and I did not use it.

So I would say that if it is discolored when you open the package it would not be worth using.

I now use all the powder make one gallon of stock solution and store it in a an accodian bottle to exclude oxygen and it is still good for making working solutions after nearly a year, despite Kodak saying it is good for 6 months stored in a full bottle.

Glass or PET (1 in the triangle) plastic bottles provide good barriers to oxygen, which causes the solutions to go bad. I use the PET bottles (plain seltzer water bottles) because they can be squeezed to exclude oxygen, they are thin-walled so the solution temperature can be rapidly changed in a water bath, they are clear so you can make sure all solids are dissolved, and they are essentially free. Just store them in the dark.