Rodinal 1:50 By Weight

RoboRepublic · Feb 15, 2021

I've been trying to speed up the setup process and decrease the amount of space by eliminating my volumetric beaker. I've tried a few times to measure out Rodinal 1:50 by weight using a scale; For 500ml (combined solution) I'm coming up with 490g of water to 16g of Rodinal.
I'd like to compare notes with anyone else who might be working in this way? It seems less error prone then having liquid sloshing around and trying to decipher where the surface of the liquid is based on the reflections in the beaker.

I know its a bit into the weeds, but its just plain faster to measure by weight for me, and if I can put the beaker away it would give me a few dollars worth of real estate back from my tiny apartment every month for.. film!

ic-racer · Feb 15, 2021

For 500ml I'm coming up with 490g of water

Formula 1 measures the fuel in the cars that way.
Your measurement are a little off as the specific gravity of water is 1.0 by definition.

RoboRepublic · Feb 15, 2021

Ah I meant for 500ml combined solution! So I think that should be 490ml of water, which should be 490g if I am understanding specific weight correctly, its been years and years since chem class!

Pieter12 · Feb 15, 2021

First, it is 1+50, not 1:50 and I believe Agfa recommended a minimum of 10ml for each roll of film being developed.

YoIaMoNwater · Feb 15, 2021

RoboRepublic said:
Ah I meant for 500ml combined solution! So I think that should be 490ml of water, which should be 490g if I am understanding specific weight correctly, its been years and years since chem class!

You’ll need to figure out the density of stock rodinal before calculating volume from its weight.

Pieter12 said:
First, it is 1+50, not 1:50 and I believe Agfa recommended a minimum of 10ml for each roll of film being developed.

There’s prob little difference if you’re adding 10 mL rodinal to 490 mL or 500 mL of water though.

runswithsizzers · Feb 15, 2021

Next time you open a new bottle of Rodinal weigh the contents and calculate the weight per mL. That weight times 10 plus 500g water should be close to 1+500 by volume.

Edit: This assumes the manufacturer fills the bottle precisely to the volume indicated on the label.

YoIaMoNwater · Feb 15, 2021

You don’t even have to open a new bottle. Just take your beaker/graduated cylinder and zero it on a scale. Pour enough rodinal so you can reach a exact volume. Take the weight then divide by the volume and you get its density.

For 1:50 dilution with 500 mL of total volume, just take your density in X g/mL and multiply it by 10. Then fill in water to 500 mL.

If I had a extra balance I would do this myself but since I don’t want to contaminate the balance in the kitchen then that’s not possible.

Pieter12 · Feb 16, 2021

YoIaMoNwater said:
You’ll need to figure out the density of stock rodinal before calculating volume from its weight.

There’s prob little difference if you’re adding 10 mL rodinal to 490 mL or 500 mL of water though.

The point is the mininmum recommended is 10 ml of rodonal for each roll of film.

Martin Rickards · Feb 16, 2021

Pieter12 said:
The point is the mininmum recommended is 10 ml of rodonal for each roll of film.

I use Foma's R09 substitute and get away with using 6 ml per 36 roll of 35 mm film.

koraks · Feb 16, 2021

RoboRepublic said:
It seems less error prone then having liquid sloshing around and trying to decipher where the surface of the liquid is based on the reflections in the beaker.

Lab 101: look at the beaker from the side so you can easily see the meniscus of the fluid and its actual surface. For measurements, you look at the actual surface. It's pretty easy to see with your eyes level with the surface.

If you want to save space and need to measure out small quantities of liquids, a syringe is an obvious solution.

Don_ih · Feb 16, 2021

RoboRepublic said:
I've been trying to speed up the setup process and decrease the amount of space by eliminating my volumetric beaker. I've tried a few times to measure out Rodinal 1:50 by weight using a scale; For 500ml (combined solution) I'm coming up with 490g of water to 16g of Rodinal.
I'd like to compare notes with anyone else who might be working in this way? It seems less error prone then having liquid sloshing around and trying to decipher where the surface of the liquid is based on the reflections in the beaker.

I know its a bit into the weeds, but its just plain faster to measure by weight for me, and if I can put the beaker away it would give me a few dollars worth of real estate back from my tiny apartment every month for.. film!

I would just pick a concentration and go with it. If you try 490g water and 16g rodinal and get the results you want -- do that every time. It's as repeatable as 500ml water + 10 ml rodinal. And I can see it would be easy to do - container on the zeroed scale, fill to 490 g water then top up to 506g with rodinal. It probably is more accurate than any attempt to measure out exactly 10ml of it.

bripriuk · Feb 16, 2021

Over the years I've tried just about everything to measure small amounts of Rodinal. This 10mm dropper is the best I've found so far:

CLICK HERE

Brian P

YoIaMoNwater · Feb 16, 2021

Pieter12 said:
The point is the mininmum recommended is 10 ml of rodonal for each roll of film.

Not sure why you’re repeating yourself but 1:50 with 500 mL total volume is using 10 mL of rodinal.

jay moussy · Feb 16, 2021

Silly question here: Does it matter if the mix is 1;50 exactly?
Or, say 1:52?
But not 1:48?

(new R09 @ 1:50 user wants to know)

titrisol · Feb 16, 2021

I don;t think it does, as long as you do it consistently (same thing all the time)
measuring R09 with a syringe is easy because it measured with 0.5 ml marks ; with measuring cylinder is 1ml
However the water/mix cylinder has 10ml intervals (+/- 2ml)

jay moussy said:
Silly question here: Does it matter if the mix is 1;50 exactly?
Or, say 1:52?
But not 1:48?

(new R09 user wants to know)

Donald Qualls · Feb 16, 2021

The difference between 1+49 and, say, 1+52 is so small (about 0.6%) that I wouldn't worry about it. If you're someone who runs a densitometer test on every roll, then you probably want to use a developer you can mix from stock with less dilution (D-76, for instance, at 1+1), to avoid having to measure so precisely. For us normal people, there will be more variations in time, temp, agitation, and exposure from one roll to another than you'll get from "best effort" measurement errors in mixing Rodinal derivatives.

titrisol · Feb 16, 2021

I don't see why not, but it all depends on the specific gravity of your concentrate
I believe (in AGFAtimes) specific gravity of Rodinal concentrate was in the 1.38 - 1.385 range so you needed 500 g of water and 13.8-13.85 g of Rodinal
BUT today you will need to calibrate this density using a syringe that measures ml accurately. Add enough water for you solution by weight, and with the syringe add slowly 2, 4, 6, 8,... ml of Rodinal and check the weights of each addition so that you have an accurate ml to g conversion

In case you havent seen this
https://125px.com/docs/techpubs/agfa/c-sw16-e15.pdf
https://unblinkingeye.com/Articles/Rodinal/rodinal.html
https://unblinkingeye.com/Articles/Developers/Times-Rodinal/Rodinal.pdf

RoboRepublic said:
I've been trying to speed up the setup process and decrease the amount of space by eliminating my volumetric beaker. I've tried a few times to measure out Rodinal 1:50 by weight using a scale; For 500ml (combined solution) I'm coming up with 490g of water to 16g of Rodinal.
I'd like to compare notes with anyone else who might be working in this way? It seems less error prone then having liquid sloshing around and trying to decipher where the surface of the liquid is based on the reflections in the beaker.

I know its a bit into the weeds, but its just plain faster to measure by weight for me, and if I can put the beaker away it would give me a few dollars worth of real estate back from my tiny apartment every month for.. film!

Martin Rickards · Feb 16, 2021

YoIaMoNwater said:
Not sure why you’re repeating yourself but 1:50 with 500 mL total volume is using 10 mL of rodinal.

My Paterson tank needs 300 ml for a 35 mm film, and 6 ml gives good results with FP4+. A 120 film takes 500 ml.

mshchem · Feb 16, 2021

I've used Nalgene PMP (polymethtylpentene) graduates for 30 years. I have 10mL, 50mL, 100mL, and larger.

https://www.usplastic.com/catalog/item.aspx?itemid=42962
These are resistant to everything that is used in a darkroom.

Donald Qualls · Feb 16, 2021

Back to the point of the original post, the most effective way I can see to simplify and streamline the darkroom process (at least in terms of diluting your developer) with a Rodinal derivative is to premeasure the Rodinal(-derived) developer concentrate. You'll want a bunch of tiny vials for your 10ml and 2.9 ml concentrate doses, and I can't vouch for the longevity of a Rodinal clone once decanted from the original bottle over the original crystals (of sulfite?).

When it's time to process, fill your mixing beaker to the appropriate line (290 ml or 500 ml) and pour in the contents of the appropriate size concentrate vial. Stir, and ready to process. As I noted previously, this is plenty precise unless you're fanatical about your sensitometry and print only graded paper (and can get only #3).

For most of the rest of us, it's sufficient to have a 10ml syringe graduated in 0.1 ml -- pour concentrate into a small beaker, draw up the necessary amount, pour the rest back into the original bottle, squirt the measured liquid into the mixing beaker, rinse the syringe with the beaker contents, close up the concentrate bottle, stir, and ready to process. A pair of marks on your mixing beaker will suffice to eliminate a large graduated cylinder. With some brands of Rodinal clone, you can draw directly from the concentrate bottle with the correct size syringe, and eliminate a second graduate. And now you don't need to mess with a scale.

Doremus Scudder · Feb 16, 2021

Uh... I don't see why you're trying to do this. Surely, you need a container for your water for mixing developer, which could easily be graduated. I'd think a couple of syringes marked in ml would take up considerably less space than a scale, even a small digital one. Syringes are easy to read and accurate. 10ml sucked up in the syringe and injected into 500ml of water. What could be easier?

But, if you really want to spend all that time figuring out density of Rodinal and weighing out water... knock yourself out.

Doremus

pentaxuser · Feb 16, 2021

Pieter12 said:
The point is the mininmum recommended is 10 ml of rodonal for each roll of film.

So one 35mm film in stand development requires a litre of solution. Does this mean that if you want to do say, 3 x135 films at once you need a 3L tank? Is there a Agfa Rodinal source for this that you can refer me to?

Thanks

pentaxuser

runswithsizzers · Feb 16, 2021

koraks said:
[...]If you want to save space and need to measure out small quantities of liquids, a syringe is an obvious solution.

If I understand correctly, it is the volume of the water that is the issue - he wants to make up the Rodinal without using his 500mL volumetric flask - or any other measure of volume once he knows the equivalent weights.

koraks · Feb 16, 2021

runswithsizzers said:
If I understand correctly, it is the volume of the water that is the issue - he wants to make up the Rodinal without using his 500mL volumetric flask - or any other measure of volume once he knows the equivalent weights.

Yes, thanks, I see it now.
Frankly, my experiences with weighing water aren't too good. A scale always has a little response time before it shows the new reading, which means you very easily overshoot the mark when trying to pour an exact amount of water. I do this a lot in the kitchen when baking bread - in which case it doesn't have to be very exact. I wouldn't enjoy doing this if it had to be done with any accuracy.

pentaxuser said:
So one 35mm film in stand development requires a litre of solution.

That, and an angel on one's shoulder.
I'd say, with stand development, all bets are off. If the purpose of the approach is basically to wear out the developer, I'd also argue that minimum required amounts of concentrate are out of the window.

Doremus Scudder · Feb 16, 2021

runswithsizzers said:
If I understand correctly, it is the volume of the water that is the issue - he wants to make up the Rodinal without using his 500mL volumetric flask - or any other measure of volume once he knows the equivalent weights.

But the water has to go into something, even if it's the film-developing tank. Easy enough to once figure out where the 500ml level on the film developing tank is and mark it (with a scratch or something) and then just add Rodinal concentrate with a syringe to that. Likely, though, he's mixing in something and pouring it into the tank, which makes the whole idea of weighing out everything a little more complicated than necessary I'd think.

Best,

Doremus

Rodinal 1:50 By Weight

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Rodinal 1:50 By Weight

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