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Chemical Dilution mixing

Shaggysk8

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This is a really stupid question, but I keep confusing myself.

Ok so I have 500ml of Rodinal and if I want to mix 1:100 my final mix is say 300ml do I divide 300 / 101 = 2.97

So I need 2.97ml Rodinal and 297ml water.

So does that really mean that I will get out of that 500ml 168 rolls of film?
That seems like loads.

I just need to double check as this saturday will be my first time developing, I might do 1:50 anyway as measuring 3ml might be hard.
 
First lets assume that by 1:100 you mean 1+100. When you get to dilutions this weak, the easy thing to do is mix a bit more than you need to keep the numbers even. So if you need 300 ml of mix, just prepare 3+300 = 303 ml of mix and then either toss the extra or go ahead and use a bit more than is called for if it won't make any difference. A tank that will hold 300 ml will probably not know the difference.

The second question is if 3 ml of active developer is enough to develop a roll of film. That is a more complicated question.

Denis K
 
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Measuring 3ml isnt hard if you have a childs liquid med doser. They come with either a bulb on the end, or look like a syringe. They are marked with the dose amount in tsp's. or ml's. I make sure the ones I get are marked in ml. when I measure , i use 3ml + 300ml.
Rick
 
The development times is 15mins thats why I was thinking 1:50 at 11mins that is at least 6ml, but it really does not seem like much, but I guess I will find out.
 
If you have a small graduate (e.g. the Patterson 45ml graduate) that is graduated in millilitres, put 40 millilitres of water in and then add enough of the concentrate to bring it up to 43 millilitres.

Matt
 
Don't mean to muddy the waters here, but about all you can cover with 300ml is maybe one 4X5 sheet in a tupperware sandwich container.
 
I have seen people say you only need 2.5ml of rodinal per roll. Agfa recommends 10ml per roll. I have used 6ml per roll of 120 and have had good results. I haven't tried only 3ml.

3ml + 297ml is actually 1+99, which is close enough to 1+100 to not matter. To make 3ml into a 1+100 dilution you would come out with 303ml of mixed developer.

edit: sorry your math is right, I was referencing the post below yours.
 
I use 1+500 for one roll of 120 film, which, I think is equal to a 36 exp 35mm roll. If you have a 2-roll tank, you could cover yourself for sure by mixing 1+500, put your reel in the bottom, with an empty reel on top. Use enough to cover the top reel, leaving a little space at the top for chem movement. For me, this is 425ml.
 
The best way (and clean) to measuring Rodinal is with 3 ml, 0,10 $, 6" long plastic pipettes.
 
In practice most people use 3ml Rodinal diluted to 300ml with water. It's more about being consistent than literal.

Greg Davis said:
A standard single roll tank for 35mm uses 250ml or 8 ounces.
Click to expand...

No, the tank you're using may take 250ml but the most common tanks in the UK and many other parts of the world, Paterson, take 275ml per 35mm reel, in practice most people use 300ml of developer.

Ian
 
A roll of 120 should contain less film than a roll of 135/36, out of the very basic consideration that a roll of 120 costs less .

I use syringes to measure small amount, the simple plastic one-use ones that are sold by the chemist's. I reuse them obviously, but being very cheap, one can afford a different 1 for every chemical you use. Syringes are very clean, you don't spill chemistry easily, not even if you snort while diluting it.

Considering that they are used to dose medicines, I expect the graduation to have "medical" exactitude.

One can use them with the needle on, in this case the syringe can go down in the flask to take the chemical substance, no need to pour it in an intermediate container unless the container is tall.

Fabrizio
 
According to Steve Anchell, "The Darkroom Cookbook" 3rd edition, using more developer is better than less for higher quality negatives. He recommends a minimum of 250ml (350 ml preferred) per 80 sq. in. of film (one roll of 36-exposure 35mm = one roll of 120 film = four 4"x5" negatives; think of each on an 8"x10" contact sheet). For D-76 this would mean using 250ml of stock solution. For liquid concentrate developers, 250ml would still be the minimum (350ml recommended). Of course, one would have to use oversized tanks (e.g., 16oz steel tank in place of 8oz for single roll of 35mm or 120); trays for LF would not be a problem.
 
Steve's right but it's not primarily the volume it's the amount of developing agent(s) required for developing the film itself. Below a certain level which is quite easy to calculate the developer exhausts to a point where development of the highlights slows considerably but shadow details continue to build up, the so called compensating effect.

Now that effect is sometimes used deliberately, what Steve's alluding to is when is done unwittingly and you don't get the contrast range that should be expected.

Ian
 
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Dead Link Removed

One of the latest published Rodinal / R09 one shot instructions by A&O in 2007.
The MINIMUM amount of Rodinal for each 135-36 or equivalent surface 120 roll film is 10ml for each film.

In practice it will be around 5-6ml for each film. Going under this limit it will depend on the amount Black and White area in your negative so this is not very consistent to do it.
Further Rodinal is pretty cheap, around Eur. 11,50 for 500ml so why take any risk?
 
For what it's worth, I'd like to see a standardization of mixing ratio notation. Personally, I find a plus to denote stock to water and a colon to denote stock to final solution to be pretty straightforward.

e.g., 1+24 is one part chemical stock, 24 parts water, and is the same as a 1:25 dilution.

Nevertheless, I see many chemicals listing ratios using colons the same way I use the plus. Just my $0.02...
 
I blame Kodak robert.

When I started bottles said 1:25 and 1+24 which is the same thing. Ok one would be in brackets.

Ilford are the most accurate with their 1+4, 1+7, 1+9 etc, which equate to 1:5, 1:8. 1:10

Agfa used the + sign as :, Kodak used all sorts and inconsistently.

Ian
 
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