Mixing just enough for the drum?

Hello everyone,

I have purchased a tetenal 2.5ltr (RA-4) kit and I want to mix just enough solution for the drum, I'm using a H75 simma colour printing drum, it says on the instructions for it, that it only requires 2 ounces/ 60cc of working chemistry (I'm guessing I'll need more?), but what would be the easiest way to work out how much I need to make the concentrate up to just for the drum, as I don't want to mix all the chemistry up at once.


Thanks in advance.


~John~

Mixing Partial Amounts of Liquid Concentrates

Let

v = the volume of working strength solution wanted.

x = the volume of concentrate needed

a = the volume of concentrate supplied by the maker

T = the total volume of working strength solution obtained by mixing the entire supply with water

x = v(a/T)


Example: The developer concentrate bottle contains a = 250ml and you want 300ml of working strength developer. The total mixed volume of the developer is T = 2.5L =2500ml.

Then

x = 300ml(250ml/2500ml) = 30ml.

So, you’d measure 30ml of concentrate and add (300 – 30)ml = 270ml of water to obtain 300ml of working-strength developer.

Bullseye said:

Hello everyone,

I'm using a H75 simma colour printing drum, it says on the instructions for it, that it only requires 2 ounces/ 60cc of working chemistry (I'm guessing I'll need more?),

~John~

Click to expand...

I don't have the Simma drum but the Jobo drum will do a 10x8 print with 50mls so I don't think there is any reason to believe that the Simma will require more than it says.

pentaxuser

That's just what I was told on the phone.... I weren't really sure TBH but since you say it doesn't then I will take your word for it

Thank you for your help


~John~

Note that you probably won't be able to re-use that 60ml of solution, or at least, not for more than a couple of prints. I'd think it would be pretty rare that you'd want to develop just one sheet. The way I work, I do at least one test sheet with a ringaround, then do multiple sheets after that (typically a few small prints and a couple of 8x10-inch prints from a single roll). RA-4 developer certainly lasts long enough for a print session, so if I were using drums, I'd want to mix up at least 500ml or so. (I use open trays, mix up a liter at a time, use it for two or three sessions over a few days, and then discard it.)

There are two ways to use the dev- well in a Jobo system anyway. One is to mix say 500ml as srs5694 says, see how many times the 60mls can be used before discarding and then run down the 500ml at that particular prints to dev ratio. The other way is to pour the 60mls back into the 500mls container, shake and repour and then discard however many mls the Tetenal kit says per 10 prints and replenish. This was what I did with a Jobo.

It might be an interesting to see if use once/twice and discard gives better quality and/or better or worse dev usage rate. I think there are those here who use once and discard but this may be the Kodak kits. Certainly this latter system is foolproof from a quality point of view. No idea how this stacks up in terms of cost per print.


pentaxuser