Rodinal dilutions

[irq506]

Ok so this is more mathematics then anything else which is not my strong point.

Ok so I was gratiously given a 500ml bottle of the original Rodinal (not the new stuff), and I want to make up a 5000ml amount of it in a +25 dilution. For those of you who are imperial Im sorry I dont actually know how to speak your language, but 5000ml is 5 Liters.

I need to know how much Rodinal I need to put in my 5L bottle so that I can fill up the rest with water and end up with a total of 5L +25 solution.

yeah i know hit me over the head with a hammer

thank you.

[grainhound]

Doesn't Rodinal go off quickly once you dilute it?

[xayraa33]

Originally Posted by grainhound

Doesn't Rodinal go off quickly once you dilute it?

yes it does Guy, mix only what you need at the moment of use.
the stock umixed Rodinal keeps fairly well in its stoppered bottle.

[colinh]

Originally Posted by thomasw_

1:25 dilution: thus 40 mL rodinal for every 1 L sol'n. so 200mL rodinal for 5 L sol'n.

Except, of course, its 1 + 25. So that it's 40 mL for every 1 L of WATER (not solution). Making 1040 mL solution.

So, it's 5 L water PLUS 200 mL of Rodinal.

If you want to make up exactly 5 L, you would (theoretically) have to divide by 26 (= 192 mL + water to make 5 L).

Now, why do you want to make exactly 5 L of solution? As pointed out, you're supposed to make up what you need *immediately* before use.

I use 1 + 50. I need a bit more than 280 ml to cover a 35 mm film so, I aim for 300 ml.

6 ml Rodinal + 300 ml water. Nice and easy. Not a disaster to have 306 ml.

colin

[venchka]

One more thing. I don't know the answer, but somewhere in the Rodinal literature is a minimum amount of Rodinal to use per 36 exp. roll of 135 film. My guess is that the 6+300 example above is pretty close to the minimum one should mix and use.

I also have a question about Rodinal's life span after dilution. Suppose I need 500ml/tank and I have two tanks to fill. If I mix a liter and use half for each tank, will the Rodinal mixture be ok for an hour or so before I use it in the second tank?

[markinlondon]

The recommendation is a minimum of 10ml Rodinal concentrate for each roll. This is a huge overestimate. I've used as little as 3ml of concentrate to give 1:100 (OK, Colin, it's really 1+99 ) in a Paterson tank with no ill effects. In fact, as I normally use 1:50 I don't think I've ever used more than 6ml of concentrate per roll.

[colinh]

So, everything's clear now?

I guess it would keep an hour, but why bother? I use Rodinal (1 + 50) partly because it's so quick and easy to make up (and because the concentrate keeps so well).

Of course, YOU NEED A SYRINGE (with needle - get the widest/biggest. You may need to explain what it's for )

So, measure 500 ml. Fill the syringe with 500 / 50 = 10 ml Rodinal, Squirt it in. Finished. Rather easy. (You end up with 510 ml solution).

Then, an hour later do the same again. (Or next day, if you happen to have forgotten

colin

PS. Since it was a maths question, for the sake of completeness - here's the OTHER sort of solution mixing problem: You really do want 500 ml of SOLUTION. The concentrate is mixed 1:4 (1 + 4). Again this means 1 part concentrate, 4 parts WATER, which gives .... FIVE parts solution.

I.e. for every 5 parts solution ONE part is concentrate, the rest (4 parts) is water.

5 parts solution has 1 part concentrate.

500 ml solution has 100 ml concentrate.

For (1 + 4) you divide the solution volume by FIVE to get the concentrate volume.

For (1 + 7) you divide by EIGHT.

And yes, for (1 + 50) you *would* divide by 51 (to get the amount of concentrate needed for exactly 500 ml of solution), but since 500/51 (~ 9.804) ml is finicky to measure, you don't bother. You just make 510 ml instead.

[colinh]

Well, the Rodinal datasheet says continuous agitation for the first minute, and then once every 30 s.

But I don't know anything about developing ask MarkinLondon.


colin

[markinlondon]

Thanks, Colin . Agitation with Rodinal is very much a question of trial and error. With APX100 I give 30 seconds to start with and then two slow turns (takes about 5 seconds or so) every minute. This gives smooth negatives for scanning or a condensor head with well controlled highlights at full box speed. I gave a similar treatment to FP4 but it's been a long time since I did any. The initial 30 second agitation seems to be important with Rodinal, I don't do this with any other developer.

My dilution is not 1+50 but 1+49. As long as you're consistent it doesn't matter as you adjust your own process to suit.

[350D_user]

How I'd work it out would be you'd need 40ml of Rodinal for every 1L, going off the 1+25 strength, so you'd need 200ml of Rodinal for your 5L mix.

... I think.

[colinh]

Originally Posted by 350D_user

How I'd work it out would be you'd need 40ml of Rodinal for every 1L, going off the 1+25 strength, so you'd need 200ml of Rodinal for your 5L mix.

... I think.

40 ml of Rodinal for every litre of what though?

1 + 25 means 1 part Rodinal PLUS 25 parts of ...


If you have 200 ml of Rodinal in 5000 ml of mix, how much water do you have in the mix?


colin

PS. In practice it doesn't matter. In maths, it does

[irq506]

EXELENT INFORMATION!
Thank you all very much.

I have currently 20 rolls to be developed and by the end of next week an additional 10, so I will make up the 5L working solution and use it up within a month. Im shooting a lot at the moment, the creative juices are flowing.

[venchka]

Originally Posted by irq506

EXELENT INFORMATION!
Thank you all very much.

I have currently 20 rolls to be developed and by the end of next week an additional 10, so I will make up the 5L working solution and use it up within a month. Im shooting a lot at the moment, the creative juices are flowing.

Originally Posted by xayraa33

yes it does Guy, mix only what you need at the moment of use.
the stock umixed Rodinal keeps fairly well in its stoppered bottle.

No way. Everyone has already said that the Rodinal goes off-deteriorates-won't work in that period of time. Mix. Use. Mix. Use. Wax on. Wax off.

[350D_user]

Originally Posted by colinh

40 ml of Rodinal for every litre of what though?

Um... battery acid...?

Originally Posted by colinh

1 + 25 means 1 part Rodinal PLUS 25 parts of ...

Water's usually the other half in those formulas.

Originally Posted by colinh

If you have 200 ml of Rodinal in 5000 ml of mix, how much water do you have in the mix?

4,800ml. Enough to make up the 5L. mix.

Do I get a gold star for maths now?

[350D_user]

Originally Posted by irq506

EXELENT INFORMATION!
Thank you all very much.

I have currently 20 rolls to be developed and by the end of next week an additional 10, so I will make up the 5L working solution and use it up within a month. Im shooting a lot at the moment, the creative juices are flowing.

Unless I read it wrong, mixed Rodinal doesn't keep for more than 2 hours, as well as the usual deterioration per film developed in it. However, the undiluted stuff will keep for a very long period of time.

[colinh]

Originally Posted by 350D_user

Um... battery acid...?

Water's usually the other half in those formulas.

4,800ml. Enough to make up the 5L. mix.

Do I get a gold star for maths now?

Excellent, so far

So you have 200 ml concentrate and 4800 of water.

The ratio is then 200 : 4800, which is ..... 1 : 24

Ooops.

But we wanted 1 : 25. Which is 200 : 5000.

The first two questions were supposed to show where the problem is. The 1 + 25, as you point out, refers to 25 parts of water. NOT of the final SOLUTION.

The Rodinal dilutions are not designed to make up nice round volumes. If that's what they'd intended they would have said 1 + 24, 1 + 49 or 1 + 99.

If that's what you're making up - big deal. I shouldn't think it matters. The thread is just about the fun of getting the maths right

Now on to the photochemistry. As has been pointed out,

DON'T MAKE 5 LITRES OF WORKING SOLUTION. IT WILL NOT KEEP.

Actually, I don't know this, not having tried it. If you want to waste a lot of Rodinal to test whether "Mix the solution immediately prior to use" instruction is valid, have a go. And show us the results.

If you want, you could do a scientific study of how long the diluted solution keeps. You would shoot the same scene 36 times. Cut the unexposed roll into strips 3" long. Make up the 5200 ml. Develop one strip immediately. One after say 30 minutes, 60, 90, 120, 180, 5 hrs, 10 hrs, 1 day, 2 days, 4 days, 1 week, 2 weeks, 1 month.

SERIOUSLY: IF YOU NEED TO DEVELOP LOTS, GET A TANK WHERE YOU CAN DO MULTIPLE FILMS AT THE SAME TIME. BUT STILL ONLY MIX UP WHAT YOU NEED TO COVER THE FILM.

colin

[Trius]

Not to muddy the waters, but ... I dilute 1:100 (or 1:25, 1:50, whatever), so use 1ml of stock to 100ml of final volume ... and it works fine. The issue is to test and get your times right, along with agitation, etc. For APX100, I use 1:100 @20C, 21 min. 30 seconds initial agitation, 5 seconds every three minutes thereafter. This gives long tonal scale and may be a bit low contrast for some scenes, but with roll film I prefer this to higher contrast since more shadow detail is good, and bringing up contrast in printing or PS is easier for me than taming high contrast. That's just me.

[d_ross]

yeah i know hit me over the head with a hammer

that's probably not a good idea really, just like mixing a months supply of rodinal isnt, unless of course you like headahces and very very thin negatives I have had bottles of rodinal concentrate that have sat half full for months and were still fine to use. But the working solution has an extremely short life.