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# Thread: Dilution question

1. Originally Posted by R.Gould
Simple anwser, divide the total required I:E 500 by the dilution +1, in your case 25, so divide 500 by 26,round it up very slightly, and you have your dilution, 20 to 480, this works for any dilution, and came from Patterson many years ago. one suggestion, when using Patterson tanks it is better to put a bit more developer in the tank, I would suggest 600, which at 1/25 works out at 24 developer to 576 water,as patterson reels can slip very slightly up the center colum, and leave a fraction of the film out of the chemicals,
Richard
Thanks for this reply. I plan to attempt all of this later today. You guys rock with all the great suggestions.

Last night I watched tv while practicing putting 120 film onto the reels. I think I have this part down.

2. Originally Posted by Steve Smith
So is a 1:1 dilution 1+0?
Yes, undiluted. Mathematically, it's the easiest way and least prone to confusion and error.

I think it's only chemists who think of 1:25 as one part in a total of twenty five.
You should think of it for what it is - a dilution factor; "one divided by twenty-five". That way you can easily determine volumes so long as you know the final volume you need. For instance, if you need 750 ml at 1:25 it would be:

725 ml / 25 df = 30 ml of developer
725 ml - 30 ml = 695 ml of water
--------------------------------------
30 ml of developer plus 695 ml of water is a total of 725 ml at 1:25

The rest of us think of it as ratio i.e. one part to twenty five parts.
Yes, I was corrupted by my high school photography teacher, too, nearly 40 years ago! Fortunately, I was straightened out by a college biology professor (who also taught photography in the department).

So 1:1 would be the same as 1+1 i.e. equal quantities of developer and water.
But 1:1 is a ratio, i.e., 1/1, which equals 1. And anything divided by 1 is undiluted, in this case, straight D-76.

3. This could be overcome by stating, simply:
One part of Rodinal, to 24 parts water.
D76 undiluted.
One part D76 to one part water.

That, to me, surpasses the 'least confusing' criteria, because it isn't even confusing at all.

4. Originally Posted by Steve Smith
So is a 1:1 dilution 1+0?

I think it's only chemists who think of 1:25 as one part in a total of twenty five. The rest of us think of it as ratio i.e. one part to twenty five parts.

So 1:1 would be the same as 1+1 i.e. equal quantities of developer and water.

Steve.
I have to agree with Steve on this. I am not corrupted by a chemist background however, I do have common sense. I may also add, it has always worked right, never a problem.

5. I know we have discussed this before but I have always thought of it like this:

1:3 can be stated as 1 to 3. i.e. one part of something to three parts of something else.

Steve.

6. Originally Posted by Thomas Bertilsson
This could be overcome by stating, simply:
One part of Rodinal, to 24 parts water.
D76 undiluted.
One part D76 to one part water.

That, to me, surpasses the 'least confusing' criteria, because it isn't even confusing at all.
But unfortunately Kodak uses 1:1 while Ilford uses 1+1, thus the potential problem. If they say in their data sheet "one part D76 to one part water" then that would be fine. But they don't.

Originally Posted by fotch
I have to agree with Steve on this. I am not corrupted by a chemist background however, I do have common sense.
I'll assume that you don't mean I don't have common sense.

I may also add, it has always worked right, never a problem.
And that's fine for you, but when communicating information to others, especially those who are new, 1:1 is more readily screwed up than is 1+1.

Originally Posted by Steve Smith
I know we have discussed this before but I have always thought of it like this:
1:3 can be stated as 1 to 3. i.e. one part of something to three parts of something else.
But to me, and many others, "1 to 3" is one part developer and 2 parts water. The "+" symbol is unequivocal while the ":" symbol isn't.

7. Originally Posted by Steve Smith
I know we have discussed this before but I have always thought of it like this:

1:3 can be stated as 1 to 3. i.e. one part of something to three parts of something else.

Steve.
Simply put, it is a RATIO not arithmetic.

A 1:3 ratio means one part something to make 3.

1 + 3 is not a ratio, it is arithmetic and means 4.

" i.e. one part of something to three parts of something else." would equal 4 and is arithmetic.

8. Originally Posted by Tony-S
But unfortunately Kodak uses 1:1 while Ilford uses 1+1, thus the potential problem. If they say in their data sheet "one part D76 to one part water" then that would be fine. But they don't.
I know that; my little recommendation was more of a dream scenario than anything. My own philosophy is to try to never use abbreviated expressions, because they cause confusion usually, as evidenced here.

9. Guys, can we please not have another 500 page thread on a topic we've all beaten to death already? :-)

I think we all know that depending on which field one is working with, 1:1 could mean straight/undiluted, because of parts vs total parts, but it's very well known to all of us, that within photo-circles, it is not parts vs total parts, but instead parts vs other parts. And since we're almost always dealing with something:water, common sense should translate 1:1 as half this, half that.

The only people who take issue with this are the ones who cannot adapt to the "corruption" of the measuring systems being used. However, I will once again reiterate that nobody ever said that it's ratio of one part : total parts, even with the ':' notation. 1:1 makes perfect sense if you think about it as parts : other parts.

If you see D-76 1:1 and you mix it straight because 'chemistry books say so damn it!' then you're not using common sense.

10. Originally Posted by Tony-S
But unfortunately Kodak uses 1:1 while Ilford uses 1+1, thus the potential problem. If they say in their data sheet "one part D76 to one part water" then that would be fine. But they don't.

I'll assume that you don't mean I don't have common sense.
the trouble wiyh common sense is thst it isn' very common.

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