Keeping Properties of Developers
We are repeatedly being contacted by analog newcomers “how long does your developer lasts” or “how long does the developer lasts after I opened the bottle”.
So we felt it is time to write a little paper about it.
Photochemisry is organic chemistry and can somehow be compared to the expiration dates on a food product.
It slowly degrades from super fresh and awesome to very well usabel, well usable, quite well usable, usable, still usable, probably still usable, possibly gone bad to “dead”.
Your joghurt does not turn bad on the day which is printed on the cap and you may possibly enjoy it even weeks later.
If we were forced to give a guarantee date, we would need to be very conservative or tolerant.
“After purchase please use up our developers within 6 months”
“Our developer XY lasts in the unopened bottle between 6 months and 100 years”.
Does this help? No, it does not.
You need to find out yourself if you do not want to constantly replenish your chemistry stock.
Keeping expectations of the unopened bottle:
- Make a judgement how long the respective product has been stored on the shelve of the dealer before it got into your hands.
If you have purchased from one of the large suppliers like Freestylephoto or Fotoimpex you can assume that every standard product has had a very short run through time. A smaller, local shop probably stored the chemistry a bit longer. In general we expect our products to arrive with the customer within 12 months after the production date at the latest.
ADOX bottles show the production date (not the keeping date) next to the barcode (exept for very small units where there is not enough space to print this information) to make this easy and transparent to our customers.
From the date of purchase we expect our products to keep at least another 12 months in the unopened, cold and dark stored original bottle.
- Storage conditions affect the keeping time.
Ideally chemistry is stored in a cool and dry, dark place at around 8°C. This is cold enough to slow down chemical processes and warm enough to keep the usually highly saturated dilutions from crystalizing out. When crystals form needed substances are missing and deterioration is accelerated. This is why photocemistry may not be frozen. If freezing happened during transport and crystals were formed redissolve your developer as quickly as possible by gently heating and gently shaking it. Check the color. It should still be quite clear. If brown sludge (tar-like) remains do not use this developer anymore.
- The bottle plays a key role
The gas diffusion capability of your bottles affect the keeping properties. ADOX is using very expensive and highly gas-blocking bottles since about 2015. These bottles have the shape of PE-HD bottles but they are as good as PET bottles. Regular PE-HD bottles are inferior and no longer used by ADOX for chemistry which is subject to oxydisation. In general you can check if your bottle is made from:
- Glas = the best option. Cat.A
- PET or ADOX PE/PA = very good. Cat. A
- PE-HD or other materials which are non blocking = inferior for developers. Cat B
In a Cat. A bottle with at least 500ml of liquid the outlined keeping properties of 24 months after production should be reasonable and easily acomplishable.
- Surface to volume equation
The larger the surface of a bottle in relation to the content inside the more important is the oxygen blocking capacity of the bottle. Small units have a by far inferior relation than large containers. On top comes that a large container has thicker walls which protect better. So to make it simple: The smaller the unit, the lower the keeping time until it spoils. 5 Liter buckets are the best in this respect. On the other hand we sell the small units so they are used up after opening. This countercompensates the keeping problems.
Keeping expectations of the bottle after opening it:
The most important question is “how much oxygen has gotten into my bottle”. The oxygen caught in the bottle reacts and uses up parts of your buffering system. When the buffer is exhausted it keeps on reacting with the developing substances and the developer starts jumping the cliff.
Influencing factors are:
- The amount of openings of the bottle- the more, the worse.
- Have you used protective gas or glass marbles to push oxygen containing air out of the bottle again? (plastic bottles can be squeezed within limits in the beginning to press out the air)
- How fresh was my developer when I first opened it? The younger the better.
- How much concentrate is left? (An almost full bottle keeps very well, a puddle on the bottom does not).
My head is spinning! How do can I tell now if my brew is still OK?
We are sorry for being so detailed but we sometimes have a hard time explaining to people why the answer cannot be a straight number.
Key indicators for a developer having gone bad are:
- Cyrstalizations. If large crystals have formed and rattle around on the bottom it does not look good for your developer.
- Decoloring. The fallout of crystals will be often acompanied by a noticeable darkening of the developer. Most developers are bad when they have turned darker than ice tea. However this is a relevant information only in comparison to the look of the developer when it was fresh. Rodinal in its many variants may come dark brown from the beginning on and still works perfectly even when it has the color of coffee. X-tol on the other hand should not be used when even a slight color change has occured (in relation to it´s color right after mixing). Ascorbic acid paper developers turn dark yellow to reddish but often still work. It really depends on the individual developer and this can only be one factor out of many to base a judgment on.
- When sufficent indicators are met (age, storage conditions, crystals, decoloring) you should perform a test with a film developer to simply check if it is still usable. This is a little work but it gives you security and helps you get the most out of your developer concentrate. The only problem is: This only works if you have made the first test when your developer was still OK. Here´s how you can do this:
- Make a mix of your developer like you would to process your next roll of film. In daylight hang in a sniplet of film (for example a piece of the tongue sticking out of a 35mm cartridge).
- Note the time it takes to completely blacken the film.
- Repeat this test with seasoned developer. If the time is off by more than 15% do not use the developer anymore. Below extend the developing time acordingly (5%, 10%..)
- With paper developers it is not that critical. You see when the developer is bad. Most paper developers should develop to full Dmax in light within less than 60 seconds. If it takes longer, blacks do not come fully and/or the color shifts to brown your developer has gone bad.
- Do not buy a large amount of chemistry if you do not intend to use it. Buy only as much as you need. ADOX is offering more than 3 package sizes in most products to make it easy to buy the right amount of chemistry.
- Consider refilling chemistry to glass bottles if it was sold in a PE-HD bottle.
- Use protective gas, squeeze the bottle or throw glass marbles into glass bottles to completely remove all air trapped above the developer
- Keep the cap/thread clean from dried developer. Dead developer (brown powder) works like a catalyst and speeds up the degrading of the remaining fresh developer. Avoid bottles with horizontal rings for this reason.
- We do not recomend squeezing-bottles (the bellows shaped foldable bottles you can buy). Inside the bellows you cannot really reach to clean and old developer might reside. But most importantly the soft plastic lets oxygen pass through. These bottles are OK to keep paper developer from one day to the next but to not buy them for long term storage of concentrates. Keep the developer in the original bottle if it is a PE/PA or PET bottle. Refill developer sold in a PE-HD bottle to a glass bottle.
- Do not use any food bottles. We did have the hospital call us up one day for a fellow who had filled Rodinal into a CoaCola bottle! Always mark chemical bottles properly!
- Last but not least: This paper is on DEVELOPERS. Do not refill your stop bath 🙂