Unicolor C-41 Mixing Question

[tron_]

Hello:

So I just picked up a Unicolor C-41 kit (2.0L) and Arista development tank. On the instructions in the Unicolor kit it says to add the powder to make a full 2L of solution.

My question is, is it okay to mix smaller quantities of the powder? For example I will be processing a lot of 120 film and on the bottom of my development tank it says for 120-220 film the capacity is 550cc (20oz).

Can I mix smaller quantities of chemicals so I do not have to make a full 2.0L worth of developer, fixer, etc all at once?

Thanks!

 

[kerne]

Yes, as long as you measure carefully. But whether you want to depends on how many rolls you have to develop. The kit says it's good for at least 16 rolls, so if you've got 8 or so mixing up 1L makes sense. if you've got more than 8 rolls, you'll want to mix up more so it doesn't get exhausted. That said, I know folks can stretch it past 16 rolls sometimes.

 

[tron_]

Thanks for the reply, I think mixing 1L would be good for me for now. What is the most accurate way of dividing up and measuring the material?

 

[kerne]

I haven't used the Unicolor powder kit personally. (I've tried the Arista liquid kit, but I don't shoot enough C41 for it to be cheaper than my local pro lab.)

For measuring other powdered chems I have a nice +/-1 gram kitchen scale. I assume the Unicolor packets are marked by weight in grams. If so, to split a 2L kit in to two 1L kits, just measure out half the total weight of each part and mix with half the required amount of water. Simple.

Also, I assume you have a way to temper your mixed chems at the recommended 100F during processing? One other suggestion, you may want to mix the blix in a glass container instead of a plastic one since adding acid to water can create heat. Although I've never had a significant problem with heat with most pre-mixed blixes. It's more of an issue if you're mixing up your own bleach with high concentration sulfuric acid such as the stuff I use for processing B&W as reversal.

 

[cepwin]

I have the 1 liter kit and I just mixed it up as per the directions and stored the chemicals in those chemical containers you can get from a photographic store (I also got those from freestyle.) I also used plastic beakers while I was processing the film with the required amount in each beaker. I ran into no problems with heat.

 

[tron_]

Hey thanks again for all the help heres what I wound up doing:

-Got a kitchen scale
-Cut everything into 1/3 (666mL) which was perfect since thats how much my tank needs.
-Got a digital kitchen thermometer to monitor temps (made sure not to cross contaminate between the developer and blix)
-Bought some nice aluminum bottles at the dollar store to store chemicals in (they were 25oz bottles, perfect for 666mL of chemicals)

I followed instructions and developed a roll of test 120 film. I'll be sure to post the photos!

 

[Prof_Pixel]

-Bought some nice aluminum bottles at the dollar store to store chemicals in (they were 25oz bottles, perfect for 666mL of chemicals)

I don't believe I'd recommend storing photo chemicals in aluminum bottles.

 

[MattKing]

I don't believe I'd recommend storing photo chemicals in aluminum bottles.

+1!

Also, good luck ensuring consistency from batch to batch.

Powdered chemistry is unpredictable - it is very difficult to ensure that it is homogeneous throughout, and generally it is impossible to tell when there is a problem (all white powder constituents tend to look similar).

If you mix it all at once, that problem solves itself. If not, there may be significantly different proportions of the various components that make up the powder at different locations in the package, and it may be impossible to ensure uniformity by re-mixing it.

 

[Photo Engineer]

Do not ever mix part of a powder kit. You can have severe problems with uniformity.

This is one of the biggest myths in photography. You can mix part of a liquid kit but not part of a powder kit! And never use aluminum for trays or storage.

PE