Best practice for mixing/storing chemicals

peen man dan · Feb 19, 2024

Hello! I just recently got the equipment to set up a dark room in my bathroom and now all I need to start making prints is the chemicals. I have a bag of D-76 stock powder and a bag of Kodak fixer each of which makes a gallon of the respective chemical solutions. I also ordered some dektol paper developer as I saw online that getting paper specific developer would save time. I obtained a variety of dark room equipment off of Facebook marketplace including three 1 liter collapsible chemical containers and other pitchers and containers for making a liter of chemicals at a time. My main concern right now is that I’d need three, one gallon containers to house the mixed stock chemicals which would not only take up a lot of space but seemingly would also need to be used in a timely manner in order to minimize waste. Is it possible to safely store the powders once they're opened in an airtight bag? That way I’d be able to make single liters of the chemicals which I could store in the containers I already have. Or is there a better way to do this? Should I look at different chemical solutions (like liquid concentrates) so I’m not being so wasteful? I am very new to the at home darkroom setup so I don’t really know what a standard consumption rate is for the different chemicals so maybe a gallon isn't a lot to use up, but I would definitely appreciate any advice here.

Kino · Feb 19, 2024

As long as you don't have children who will mistake them for soda, you can use dark colored plastic 2 liter bottles to store the surplus chemicals. Even if you don't have children, make BIG signs on the containers (skull and crossbones type) to show what is inside.

Mixing partial solutions from powder is generally not encouraged, but I do know some people have done it in the past, but I will not.

Too much of a chance of getting unequal amounts of components in each measure.

There will be a LOT of comments on this thread...

peen man dan · Feb 19, 2024

Kino said:
As long as you don't have children who will mistake them for soda, you can use dark colored plastic 2 liter bottles to store the surplus chemicals. Even if you don't have children, make BIG signs on the containers (skull and crossbones type) to show what is inside.

Mixing partial solutions from powder is generally not encouraged, but I do know some people have done it in the past, but I will not.

Too much of a chance of getting unequal amounts of components in each measure.

There will be a LOT of comments on this thread...

Thank you for the reply! I do not have any children (only cats who cannot read one way or another) but I intend on keeping all the chemicals and darkroom supplies in a closet or otherwise out of reach. I’m not super worried about messing up the ratio when creating partial solutions from the powder cause I figure as long as I have an accurate enough scale I can calculate the correct volume to weight ratio of the water to powder pretty precisely. I’m mainly concerned with the powder going bad really quickly after opening it resulting in more waste than if I made a gallon of the solution all at once.

Kino · Feb 19, 2024

It's not the ratio to water, it's the ratio of the base components WITHIN the powder.

However, if you do a search in Photrio, you will find a few threads where this is debated extensively.

I would just say, if you find your process not reacting consistently from batch to batch, this might be the problem.

To each their own.

Good luck!

Brendan Quirk · Feb 19, 2024

The idea is that the different powders may not be evenly distributed in the bag. The heavier ones may settle to the bottom etc. I use to weigh out and mix just a part of the bag without problems, but I really shook up the bag first.

MattKing · Feb 19, 2024

Some of the packaged products have very small amounts of some of the constituent components in them, and it is difficult/impossible to ensure homogeneity throughout the package. There is no guarantee that shaking the package will accomplish that.
The likelihood of inconsistent results - session to session - is relatively high.
That may not matter much with print developer, but it can create real problems with film developer.

uranylcation · Feb 19, 2024

It is possible to divide the mixed powder into smaller portions, but it's more complicated than just weight, say a quarter of whatever in the bag and make 1 liter solution.

The powder is a mix of different solid chemicals, and it's not homogeneous. Denser and smaller particles tend to aggregate at the bottom of the bag while lighter and bigger particles tend to stay on the upper layer. If you simply weight out a portion, it's highly likely you get more of a certain chemical in one batch than the other.

A better method, although would not eliminate the problem, is first to shake the bag well. Then tear open a corner, and slowly and steadily pour everything onto a large sheet of paper/aluminum foil. The powder would naturally form a cone. You want this cone as symmetrical as possible, by keeping your hand steady during the pour. Now, like in the movie, use a sharp razer blade to cut the cone from top to bottom as vertical as possible and separate the two piles slightly. Now you have divided the powder into two equal parts. You can further divide each pile into two, but cutting from top to bottom. Now you have four equal piles, for 1 liter each. This process is call sub-sampling, and is widely used in analytical chemistry to get a small representative sample from a larger sample, although it's more complicated than what I described. But for mixing darkroom chemicals that's good enough.

Saganich · Feb 20, 2024

I divide large volume stocks into smaller glass bottles without airspace. They will last a long time that way. BUT don't use the collapsible bottles for long term storage. Plastic isn't gas tight, so air will diffuse into the bottle over time.

Sirius Glass · Feb 20, 2024

uranylcation said:
It is possible to divide the mixed powder into smaller portions, but it's more complicated than just weight, say a quarter of whatever in the bag and make 1 liter solution.

The powder is a mix of different solid chemicals, and it's not homogeneous. Denser and smaller particles tend to aggregate at the bottom of the bag while lighter and bigger particles tend to stay on the upper layer. If you simply weight out a portion, it's highly likely you get more of a certain chemical in one batch than the other.

A better method, although would not eliminate the problem, is first to shake the bag well. Then tear open a corner, and slowly and steadily pour everything onto a large sheet of paper/aluminum foil. The powder would naturally form a cone. You want this cone as symmetrical as possible, by keeping your hand steady during the pour. Now, like in the movie, use a sharp razer blade to cut the cone from top to bottom as vertical as possible and separate the two piles slightly. Now you have divided the powder into two equal parts. You can further divide each pile into two, but cutting from top to bottom. Now you have four equal piles, for 1 liter each. This process is call sub-sampling, and is widely used in analytical chemistry to get a small representative sample from a larger sample, although it's more complicated than what I described. But for mixing darkroom chemicals that's good enough.

PE, Photo Engineer, a former Kodak film and chemical research and development engineer who contributed to this website for decades advised against mixing partial packages of chemicals. Take some time to search out his posts and threads and you will find a wealth of information.

Doremus Scudder · Feb 20, 2024

Collapsible, accordion-style bottles are bad. The idea was good, but they have to be made of permeable plastic, which defeats the purpose, plus the pleats fail much too often.

Powdered fixer is really from yesteryear. Liquid rapid fixer concentrates are better and more easily stored. You can mix just what you need for a session or mix a liter for film developing, etc. The rest of the concentrate keeps for months in its original container.

Print developer like Dektol is best mixed and then stored in smaller glass or HDPE bottles till needed. Then mix what you need for the session.

Many film developers come in liquid stock form (HC-110, PMK, Rodinal, Pyrocat, etc.) and can be mixed in the quantities you need just prior to use. Otherwise, when mixing larger quantities of stock, these should also be stored divided into several smaller air-tight bottles.

Stop bath is easy, just mix what you need for a session from concentrate. If you use a citric-acid stop, like Ilfostop, it does not store well (grows mold/slime). I'd just use it one-session. Acetic-acid stop baths, like Kodak Indicator Stop, keep indefinitely in working-strength solutions, so you can use them till they are exhausted. FWIW, distilled white vinegar diluted to 1.5-2% makes a fine stop bath, but without the indicator. You just have to monitor throughput to know when to discard it.

Hope this helps,

Doremus

mshchem · Feb 20, 2024

Oh if only you would have bought liquid chemicals to start.
Rodinal, Ilford rapid fix etc.

In the meantime just go ahead and split the powders, it's not a good practice. Better to mix and store it in smaller bottles.

Personally I would put the powders on a shelf and start with liquid chemicals. The powders will keep if you don't open.

foc · Feb 21, 2024

I know that it is often not recommended, but I have, in the past, split a 3.8L pack of Kodak D76.

You can read the details here.

https://www.photrio.com/forum/threads/kodak-d76-capacity.198684/page-5#post-2674575

https://www.photrio.com/forum/threads/kodak-d76-capacity.198684/page-5#post-2674622

peen man dan · Feb 21, 2024

I appreciate all the advice from everyone! I already have the powder so I’m definitely going to use that, but the next time I need chemicals I will be getting the liquid concentrates seeing as those seem a lot easier to work with. Based on the suggestions here and other info I’ve found online I think I’m gonna go ahead and mix the full gallons and keep them in some plastic jugs I already got. I saw another post that suggested using canned air to flush out as much oxygen as you can from the top of a plastic container before closing it so I'll try that. I’m not too worried about oxygen seepage into the containers, but I’m gonna plan on doing a lot of processing with the chemicals in the first couple months after I mix them to get the most out of them just in case they do start to degrade.

Doremus Scudder · Feb 21, 2024

Do divide the gallon of developer (both print and film) into smaller bottles, e.g., four quart bottles or, better 3 quart bottles and two pint bottles (which can be refilled from the next quart when you get to it). You'll extend developer stock shelf life significantly.

FWIW, I always found mixing gallon quantities of chemicals bothersome. Get yourself an oversize bucket and calibrate it with marks on the inside (Sharpie or scratches or whatever).

Best,

Doremus

Don_ih · Feb 22, 2024

If you have a gallon pack of D76 and intend to use it one-shot at stock or 1:1, you can mix the packet into a half-gallon of water that can be stored in a 2-litre bottle and dilute it as you use it. Takes up less space and is potentially longer-lasting. @Donald Qualls mentioned once he did that and it lasted a very long time. The same could be done with Dektol.

guangong · Feb 22, 2024

Kino said:
As long as you don't have children who will mistake them for soda, you can use dark colored plastic 2 liter bottles to store the surplus chemicals. Even if you don't have children, make BIG signs on the containers (skull and crossbones type) to show what is inside.

Mixing partial solutions from powder is generally not encouraged, but I do know some people have done it in the past, but I will not.

Too much of a chance of getting unequal amounts of components in each measure.

There will be a LOT of comments on this thread...

Ditto. Kodak warns against partial use since chemicals can physically separate in package. The easy solution is to make developer from components as needed, or perhaps more practical, to use developers such as Rodinal or other liquid developer, which keep well.

Donald Qualls · Feb 22, 2024

Actually, I've done it with Dektol that was several years expired when I mixed it. I last used some of it four years ago and got slightly uneven development, so it probably "only" lasts about ten years in airtight jars at double stock strength -- but that's how I'll mix my next batch of D-72, since it worked so well and so long.

Richard Jepsen · Feb 22, 2024

I see the OP is new to developing. I advise making everything simple.

- Do not try use partial bags or store chems in an open bag as other posters cautioned
- 1L mineral water bottles made from hard plastic work great for storing film developer and fix
- Use a liquid fix such as TF-5
- Use a concentrated liquid paper developer such as Ilford Multigrade.
- Use a water stop for film developing.

The above tips reduce the footprint of stored chems and maximize convenience.

ID-11 in 1L size is available where as D-76 more common in 1gal packages. 1L quantity can avoid the issue of having 6 month old film developer. However you may shoot a lot of film and storage of 1gal not an issue. I always keep a second spare package ID/11 available. 1D-11 (same as D-76) has avoided Kodak brand package failures, provides development times for nearly all films. Don’t concern yourself on the cost of developers. In the big picture its minor. Fresh developer is important to produce top repeatable results.

Support Ilford and help them remain a viable manufacturer of quality Ilford paper and films.

Sound advice from the greats.

Stick to one developer and one film until you mastered their nuisances And have reason for a different result. A classic general purpose developer like ID/11 & D-76 is the starting point. Tri-X or FP4 are the films matched for the identified developer. In the case of Tri-X that film is more forgiving of small exposure errors.

Donald Qualls · Feb 28, 2024

Richard Jepsen said:
Fresh developer is important to produce top repeatable results.

This is truth, though the definition of "fresh" may lead to some, um, discussion...

Kino · Feb 28, 2024

Donald Qualls said:
This is truth, though the definition of "fresh" may lead to some, um, discussion...

Like using my 20 year old Metol and HQ to make a "fresh" batch of D76?

It's been stored properly; works fine...

Sirius Glass · Feb 28, 2024

Donald Qualls said:
This is truth, though the definition of "fresh" may lead to some, um, discussion...

Example: I have mixed Stock XTOL in 1 liter bags that has lasted, unopened for years and is still good. When I do go to use it, I will test it on a strip of film, as I would with any developer.

Best practice for mixing/storing chemicals

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