Question about mixing chemistry from raw chemicals.

[fiddle]

Hello all,
I was interested in mixing my own developers from raw chemicals. Have sourced all I need for D72 and Mytol.
My question was with minimum amounts. I was curious if its at all possible to mix lesser amounts than the 1L the recipes call for? aside from mixing very small amounts for some of the chemicals that might be an issue,was not sure if halving one of the recipes would not have enough activity, etc.

Thank you.

 

[Doremus Scudder]

You can mix whatever volume of developer you need; just scale the recipe up or down from the one-liter formula. It's just convention that photographic-chemistry formulae are given in one-liter volumes. You can mix 500ml by cutting everything in half, or two liters by doubling everything, etc. The proportions need to be the same, that's all.

Best,

Doremus

 

[fiddle]

Thank you Doremus.
My concern was with activity minimums, as in xtol needing 100ml dev minimum per 35mm roll, etc. (or something like that)
Thanks again, appreciate it.

 

[koraks]

My concern was with activity minimums, as in xtol needing 100ml dev minimum per 35mm roll, etc. (or something like that)

That's unrelated to mixing the chemistry yourself, and is specific to the developer. Consult the documentation of the developer and/or online lore.

 

[MattKing]

For some recipes, cutting the volume down can create challenges if for any of the components very small amounts are required. The required precision of measurements being the issue.

 

[MattKing]

Thank you Doremus.
My concern was with activity minimums, as in xtol needing 100ml dev minimum per 35mm roll, etc. (or something like that)
Thanks again, appreciate it.

That won't change - just make sure you mix enough and use enough to deal with that.

 

[fiddle]

Appreciate it all.

 

[Alan9940]

For some recipes, cutting the volume down can create challenges if for any of the components very small amounts are required. The required precision of measurements being the issue.

This can be true for a normal amount of developer, too. For example, FX-55 has 0.1g added to 1L when making up a working solution of this developer. How I handle these very small quantities is to make up a percentage solution. I make a 1% Phenidone solution by dissolving 1g Phenidone in 100ml of propylene glycol, then add 10ml of this solution to my FX-55 working solution. This idea may work when other very small weights of raw chemical is needed, but I've only ever done it with Phenidone.

 

[koraks]

Appreciate it all.

Always welcome; have fun with mixing your own chemistry. I've always enjoyed it.

 

[xkaes]

As mentioned, percentage solutions is one approach, but it has its shortcoming too.

I've created tables for my chemicals for mixing 10 oz, 20 oz, 1000ml & 2000ml amounts. More often than not, I just need only 10 or 20 oz., but as mentioned that means really small amounts of some of the chemicals. This is easily handled with a scale that measures 100th of a gram. I use an OHAUS Cent-O-Gram that measures up to 311 grams at 0.01gr accuracy. These, and others, are very inexpensive used.

 

[dynachrome]

I don't think mixing batches smaller than 1 liter / 1 Quart is practical. Developers seem to last longer when they are mixed to make at least that much. Mixing smaller quantities may mean storing in very small bottles. There are developers like Rodinal, HC-110 and the late and lamented Edwal FG-7 which came in liquid concentrates and were easy to dilute for use. Rodinal is not suitable for with all films and HC-110 has changed a number of times and may or may not keep as long as it used to. I have enough sodium sulfite and metol to make a lot of D-23. For now I am mixing it up a liter at a time. If some doesn't get used while it is still active, I can live with that.

 

[xkaes]

I don't think mixing batches smaller than 1 liter / 1 Quart is practical. Developers seem to last longer when they are mixed to make at least that much. Mixing smaller quantities may mean storing in very small bottles.

Or, as I do, use once. For 10 oz of whatever working solution, the amount and cost is pretty close to free.

 

[koraks]

Developers seem to last longer when they are mixed to make at least that much.

There's no direct relationship between volume and shelf life as such.
Of course, if you mix 100ml of D72 and store it in a 1000ml bottle, there will be a lot of air on top and that will make the developer oxidize sooner. However, if you store it in a 100ml bottle, it'll have the same shelf life as 1000ml of the same developer in a 1000ml bottle.

The main determinants to unused developers going bad, in real life, are (1) the formulation, (2) exposure to oxygen and sometimes (3) temperature.

 

[Donald Qualls]

Another thing you can do with D72 to prolong its life (I've done this with commercial Dektol that came in a "makes 5 gallon" package and was free) is to mix with half the water. Dektol will all dissolve at the listed temperature (and by analogy, D72 ought to), and it will keep for years in closed bottles with minimal air space. Of course, you need to mark the container to you know to compensate the dilution when you use the developer...

 

[dynachrome]

Years ago I ordered several small bottles (16 oz?) of NACCO film developer. All were bad. The larger size bottles were OK. Were the smaller bottles older? Did they sit around longer? I don't know. NACCO is long gone. I was disappointed when Edwal FG-7 went from being sold in brown glass bottles to being sold in plastic bottles. The shelf life was reduced drastically.

 

[cmacd123]

I was disappointed when Edwal FG-7 went from being sold in brown glass bottles to being sold in plastic bottles. The shelf life was reduced drastically.

so was I -I never had any problem with FG7 in the glass bottles, it was my "go to " developer, but my usage was in fits and starts. several batches one month, and two months before the next batch. last bottle I bought was in the "easy Measure" Falcon plastic bottle. did one batch of film fine, but a few months later RUINED a batch of film, with 3/4 dead developer.

I understand that is an issue with the plastic bottles of Rodinal also

 

[Augustus Caesar]

1 liter is probably the smallest quantity that can be consistently measured out for most developers. D-76 after all, needs only 2 grammes of metol.

 

[MattKing]

If you are asking about much smaller than 1 litre volumes, that is challenging.
But something like 0.5 litres at a time, that is quite accomplishable.

 

[fiddle]

It would probably be .5 liter. I don't develop /print very often. Sometimes I'll do a bunch then a few months later I go back and dev is dead. Mix a new batch etc.

Figured making my own, I can mix a fresh batch if in doubt, and much cheaper than buying a 5L batch of whatever.

Also since dektol 1:2, xtol 1:1. If I mixed a full liter, would have a bunch to throw away if I were to not dev for a while. Mixing .5 would be less waste if that's the case.
I have a scale that supposedly reads down to .001 grams. So should be possible. Time to put this scale to the test.

Thanks again for all the helpful replies.

 

[Anon Ymous]

1 liter is probably the smallest quantity that can be consistently measured out for most developers. D-76 after all, needs only 2 grammes of metol.

250ml is IMHO perfectly doable and I've done it without any problems.

 

[koraks]

250ml is IMHO perfectly doable and I've done it without any problems.

Indeed, and usually smaller as well. For most developers I often start out with test batches of, say, 150ml, or even 50ml for concentrates. Then scale up as desired.

 

[lamerko]

Mytol probably won't last long, so there's no point in mixing large amounts. As for D72 - it should be relatively stable in a tightly closed bottle.

 

[Donald Qualls]

D-76 after all, needs only 2 grammes of metol.

If you have a decent scale, it's no big deal to measure out 0.2 grams to make 100 ml of D-76 stock. I have one I've had for more than forty years that will measure 0.1 grain (15.4 grains to the gram) and one I got recently that measures to 0.1 gram without presetting. The latter was sold as a kitchen scale.