Please can someone help me with how to dilute chemicals successfully?

[still_learning]

Hello! I just posted this on another photography website forum and they were quite nasty about it and didn't help but instead chose to tell me how doomed i am if i cannot understand this simple thing.

Okay, i really should know how to measure out the ratios of darkroom developer/stop/fix etc, since i am at college, but i really don't. Everyone used to just get there first and practice and i would be like, oh, that's fine - everything is set up. And recently, i've been avoiding doing it because i might make a mistake and i shouldn't be at this stage!! ): For example, i don't understand the ratios '1:4 / 1:1' etc
Can someone explain how you know the amount of water etc to add and how the ratios work? Probably doesn't help that i'm not wonderful at math, right?
Please be patient and use layman's terms! I'm not always up to date with the darkroom language! Also, please don't tell me to ask my tutor or classmates. I'm posting this here for a reason!
Thanks! :blushing:

 

[Helen B]

Although there are two different conventions for what 1:4 etc might mean, the one most common in photography is 1 volume of developer concentrate to 4 volumes of water to give a total of 5 volumes. The first number is the developer and the second is the water, usually all by volume. Therefore to make, say, 250 mL of working strength developer, you would first divide by 5 to get one volume unit, ie 50 mL. Then 1:4 becomes 50 mL of developer concentrate to 200 mL of water to give 250 mL.

It's a lot clearer if the notation X + Y is used, eg 1+4. One volume of developer concentrate plus 4 volumes of water. Some manufacturers use that notation, and I prefer it because it is less ambiguous and easier to work out if you do not know which convention is being used.

There is also a convention that 1:4 means 1 volume of concentrate to 4 volumes of working solution, ie 1+3, but that is not common in photography.

It should be clear whether the ratios refer to volume or weight. With liquids it is usually volume.

 

[still_learning]

Thank you so much Helen! I'm beginning to understand it now. College on Monday will be a lot less confusing.

 

[Redeyejedi]

you too, can arrive early and practice. or show up during another time of day and practice/observe/inquire. college darkroom chemistry is replenished quite regularly...at least it was when i went.

also, gugel is your friend http://web.mit.edu/6.163/www/Resources/Basic_Darkroom_Rules_rev2.pdf
good luck, have fun and have test strips pre-cut

 

[gsgary]

For a roll of 35mm my patterson tank i need 300ml so for 1+4 you want 75ml of developer to 300ml of water

 

[Helen B]

Why not 60 mL developer and 240 mL water? Minimum recommended developer volume?

 

[Compaq]

What I have learned in my laboratory classes (I study chemistry), and the way I interpret these things, is as follows:

As already mentioned, there are different conventions. 1+4 and 1:5 actually means the same thing, it's just two different ways of showing the relationship between the constituents in the mixture.

1) I use Ilfotec DD-X as my film developer. The bottle says I'm to dilute it 1+4. Now, what does this mean? It means one part of the first liquid and four parts of the other. Since we're diluting the concentrate, it makes sense to use one part developer solution and four parts water. Then we have diluted the concentrate 1+4.

2) The bottle could just as easily have informed me to dilute the concentrate 1:5. This means that one fifth of the total volume is the developer solution. The rest would be water.

We need some concrete examples to hang this up on. I will use the same example for both ways.

1) I'm developing 1 film. I decide that I will have a total volume of 500 mL to be sure that the entire reel is covered by the solution. Let's say I'm using Rodinal, and I need to dilute to 1+24. So, one part rodinal and 24 parts water must equal 500 mL. Let's be a little more mathematical, and put up a simple equation that expresses our problem:

x + 24x = 500 mL. We need 24 times more water than rodinal concentrate, and the sum of these is 500 mL. We add the x-es, divide both sides by 25 and find that x = 20 mL. Remembering that one x represents the one amount of rodinal (1+24, remember?), I now know that I need 20 mL rodinal and 24*20 mL = 480 mL water. 20 mL rodinal and 480 mL water add up to 500 mL working solution, which is what I wanted. See how this worked? This is what I like to do when I need to calculate. With a few tries you see what the equation looks like, and you just enter the numbers on your calculator.

2) Same problem. I want 500 mL working solution, with the concentration of rodinal equals 1:25. In my final solution, one twentyfifth of the total volume is supposed to be rodinal concentrate. Okay, easy! I divide 500 by 25, and find that I need 20 mL rodinal. The rest should be water, and 500 mL - 20 mL = 480 mL. There, I've found the amounts of both constituents!

If we're working with extremely diluted solutions, it may make more sense to write 1:1000 rather than 1+999. If I just need to get an idea of how diluted some solution is, I find 1:1000 easier to grasp. I have a feeling that the convention in scientific articles is to report concentrations by 1:1000, and not 1+999. I can't back that statement up, so take it with a grain of salt. Either way, you should understand both, but you may like one over the other

I hope I didn't confuse you even more!

 

[Helen B]

Anders, as I explained in my first post the convention in photography is that 1:4 means 1+4, not 1+3. This is quite important -all explained in my first post.

 

[gsgary]

Why not 60 mL developer and 240 mL water? Minimum recommended developer volume?

I like wasting Rodinal, but the dilutions are that small with Rodinal there is minimal waste sometimes im using 1+100

 

[timor]

Anders, as I explained in my first post the convention in photography is that 1:4 means 1+4, not 1+3. This is quite important -all explained in my first post.

Agreed. No matter how it sounds, that the convention in photography. Sure, Ilford is much clearer with "+" and Kodak more confusing with ":" sign, but Anders you have to remember, that Americans are still using Imperial system of measurements and THAT confusing. I would like to see you implementing that rations using pints and gills. And remember : US pint is diffeerent from (nomen-omen) Imperial pint..

 

[gsgary]

Anders, as I explained in my first post the convention in photography is that 1:4 means 1+4, not 1+3. This is quite important -all explained in my first post.

Agreed. No matter how it sounds, that the convention in photography. Sure, Ilford is much clearer with "+" and Kodak more confusing with ":" sign, but Anders you have to remember, that Americans are still using Imperial system of measurements and THAT confusing. I would like to see you implementing that rations using pints and gills. And remember : US pint is diffeerent from (nomen-omen) Imperial pint..

I'll be using pints tonight :cheers:

 

[Compaq]

Darn non-logical, anti-intuitive and un-disciplinary conventions, then I apologize for confusing!

If I ran across a 1:25 on a bottle, I'd dilute it as 1+24, but I'll try to remember that that's wrong. Thanks for clarifying, Helen!

 

[timor]

I'll be using pints tonight :cheers:

I hope imperial (BIGGER !)

 

[gsgary]

I'll be using pints tonight :cheers:

I hope imperial (BIGGER !)

No pints having more tonight, Going to start off with a local brew from Spire brewery called Lighter shade of pale, American IPA here Find Real Ale Pubs, Bars in Chesterfield. Beer, Food, Music, Events at The Beer Parlour

 

[andrewprell]

Darn non-logical, anti-intuitive and un-disciplinary conventions, then I apologize for confusing!

If I ran across a 1:25 on a bottle, I'd dilute it as 1+24, but I'll try to remember that that's wrong. Thanks for clarifying, Helen!

Not necessarily wrong, mixing various dilutions can give you different images. Fun to experiment with such things.