A question......stupid or not

[spb854]

Looking over various data charts, I see dilutions stated as:

1:25
1:50

and then I see:

1+25
1+50

My question................

1:25 = 1+25 ???

 

[BWGirl]

Looking over various data charts, I see dilutions stated as:

1:25
1:50

and then I see:

1+25
1+50

My question................

1:25 = 1+25 ???

Yep, they mean the same thing... mix 1 part of whatever with 25 parts of something else.
Not such a stupid question. I had to ask that myself when I first started developing film & doing my own prints!

 

[spb854]

BUT....when mixing HC-110 to make a batch use from original product,
i.e. 300 ml the literature says to use like 6 ml in 294 ml water.

That is NOT what you're saying. If I did it as you say, the volume would be
306ml.

See what I mean.

 

[dslater]

BUT....when mixing HC-110 to make a batch use from original product,
i.e. 300 ml the literature says to use like 6 ml in 294 ml water.

That is NOT what you're saying. If I did it as you say, the volume would be
306ml.

See what I mean.

If you're mixing 6 ml in 294ml, then you're using 1:49 ( 1 part HC110 to 49 parts water) or 1+49 ( 1 part HC110 plus 49 parts water ) - both of which yield 300ml solution.

 

[Bruce Osgood]

Kodak started this mix up many years ago. They would indicate something as 1:9 when they meant 1 + 9, or a total of 10.

When chemists say 1:9 they are saying take 1 and dilute it into 9, for a total of 9.

In the world of photo chemistry it doesn't make much difference.

 

[dslater]

When chemists say 1:9 they are saying take 1 and dilute it into 9, for a total of 9.

Hmm - that doesn't make any sense to me - if I take 1 ml and dilute it into 9 ml, I'll have a total volume of 10ml

 

[dslater]

In the world of photo chemistry it doesn't make much difference.

Well - for 1:9 it doesn't make much difference, but if it's more like 1:2 or 1:3, then it makes quite a difference.

 

[Bruce Osgood]

Well - for 1:9 it doesn't make much difference, but if it's more like 1:2 or 1:3, then it makes quite a difference.

Yes it does make a big difference.

Hmm - that doesn't make any sense to me - if I take 1 ml and dilute it into 9 ml, I'll have a total volume of 10ml.

Well then, I wasn't clear. Take 1 ml and add 8 and you have a 1:9 dilution. If you wind up with 10 then you have added 1+9.

 

[Neal]

Dear Bruce,

If chemists use a ratio of 1:9 and end up with 9 total parts, how do they handle the ratio 1:9:1?

Kodak did not make a mistake in their use of ratios.

Neal Wydra

 

[jstraw]

Doesn't it indicate "parts" in both instances and not ratios?

 

[Steve Smith]

Doesn't it indicate "parts" in both instances and not ratios?

I think that's the general understanding now. The colon traditionally refered to a ratio though or in the case of an engineering drawing, a scale (which is also a ratio). e.g. scale 2:1 is twice full size.

We had a long thread about this a few months ago. I remember that at the time I couldnt find any literature with 1:x style dilutions, just 1+x.


Steve.

 

[BWGirl]

BUT....when mixing HC-110 to make a batch use from original product,
i.e. 300 ml the literature says to use like 6 ml in 294 ml water.

That is NOT what you're saying. If I did it as you say, the volume would be
306ml.

See what I mean.

Yes, that IS what I am saying. I made up a handy-dandy little chart which I slipped into a plastic page protector. It contains many of the different dilution ratios and also how much of what to mix with what to make the solution. If you would like, I'd be more than happy to email you a copy! Just pm me with your email address.

 

[Michel Hardy-Vallée]

When you take a chemistry class, you're expected to be able to make a x% solution of something. The percentage is an accurate measurement of the concentration. A percentage solution takes into account the final volume of the solution (if, for e.g. you are mixing two liquids).

On the other hand, if you ask amateur photographers to make a x% solution of something, you'll have as many answers as you have photographers, and they will all say their method is best. So conscientious manufacturers just tell people to measure 1 unit of stuff with X many units of water. That's usually applicable to liquid concentrates. 1+50 is supposed to be the same as 1:50, but ":" also is used for ratios and can look like a percent solution. I use "+" myself to avoid ambiguities, like Ilford and Agfa do (good rational Europeans!).

The one thing that sometimes confuses me is the "add water to make..." When you mix powdered developer, you start with, say, 4L of water, dissolve the powder and then you add water to make 5L. Well, I personally measure 5L of water, use the first 4L to dissolve, and add the extra 1L after. I just assume that all the little developer molecules will tuck themselves quietly between the molecules of water.

It nearly bit me in the ass when I was mixing RA-4 developer yesterday. I had a 1-Gallon kit, and the liquids were 20oz. Had I used my usual technique, my developer would have been too dilute in excess of 20oz of water. I discovered this as I was mixing the liquids, actually.

Of course, a consistent mistake sometimes ceases to be a mistake, but at least with colour processing I wasn't feeling like losing my time readjusting everything to the "new" concentration.

 

[Sparky]

My understand has always been that kodak followed the IUPAC (or whatever) convention and 1:3 would mean one part reagent for a total of three parts - and that ILFORD broke with the tradition - their 1+3 always meant a total of FOUR parts - but since then - more people are adopting the ilford convention because the procedure is somewhat implicit in the formula...

So - you all mean to say that I was mixing my HC-110 11% or so too strong throughout the 80s....????

 

[Neal]

There is no ambiguity, only misunderstanding. Even in the use of ratios in an engineering drawing. If you are using a ratio of 1:3 and ending up with 3 parts, you are doing it incorrectly. For all those who think a ratio of 1:3 means you end up with a total of 3 "parts", how do you handle ratios of more than two components? How do you deal with a ratio of 1:1?

Neal Wydra

 

[Akki14]

I think I'm more confused now than ever. I'll try to stick with my theory of add numbers up and divide the needed amount of liquid by that number:confused:

 

[Bruce Osgood]

Dear Bruce,

If chemists use a ratio of 1:9 and end up with 9 total parts, how do they handle the ratio 1:9:1?

Kodak did not make a mistake in their use of ratios.

Neal Wydra

Neal,
Is 1:9:1 A RATIO? I don't think so. Perhaps a formula or recipe. A ratio is a relationship between two things, not more than two. In a Pyrocat HD working solution you are not directed to use 1 : 1 : 100 but 1+1+100, that is not a ratio.

 

[Bruce Osgood]

How do you deal with a ratio of 1:1?

Neal Wydra

Straight Stock Solution. Not diluted

 

[smieglitz]

BUT....when mixing HC-110 to make a batch use from original product,
i.e. 300 ml the literature says to use like 6 ml in 294 ml water.

That is NOT what you're saying. If I did it as you say, the volume would be
306ml.

See what I mean.

If your question is about HC-110 specifically the formula has been compounded so that dilution B for example will have 1 ounce of developer concentrate mixed with 31 ounces of water (1+31) to bring the total volume to 32 ounces.

The dilution from the stock solution is 1 + 7 for dilution B. The stock solution has been mixed 1 + 3 originally (= 16 + 48) so that in 1 ounce of stock there will be .25 ounce of concentrate.

To get 32 ounces of working developer one would take 4 ounces of stock (containing 1 ounce of concentrate total or 4 x .25) and add it to 28 ounces of water (4 x 7) to bring it to 32 ounces total (which still only contain 1 ounce of concentrate) hence the 1+31 dilution from concentrate.

This means that 1+31 ≠ 1:31 at least according to Kodak.

Joe

 

[dslater]

The problem here is the overloading of the : operator. mathematitions and chemists intrepret x:y to be the ration x/y. However, in many photochemical recipies, x:y is intrepreted to mean x parts + y parts to make a total of x+y parts. This is indeed an incorrect use of the : operator. The best wasy to insure there is no ambiguity is for a recipie to always specify what the total volume should be. i.e. 1:9 for a total of 10 or 1+9 for a total of 10 - and it would probably be better to just stop using the : notation entirely.
While the : notation may be quite useful to a chemist who is discussing a mixed solution, it is not so useful for a non-chemist who is just trying to mix up some developer.

 

[Andy K]

Well then, I wasn't clear. Take 1 ml and add 8 and you have a 1:9 dilution.

No, you have a 1:8 dilution.

1:9 is a ratio, 1 part developer to 9 parts water, resulting in a volume equal to 10 parts.

 

[Neal]

Dear Bruce,

I admit my (embarrassingly obvious) error in terms of a ratio being limited to 2 components. However, a dilution of 1 part of "A" with 1 part of "B" still gives you 2 parts.

Neal Wydra

 

[Bruce Osgood]

.....The best way to insure there is no ambiguity is for a recipie to always specify what the total volume should be. i.e. 1:9 for a total of 10 or 1+9 for a total of 10 - and it would probably be better to just stop using the : notation entirely.
While the : notation may be quite useful to a chemist who is discussing a mixed solution, it is not so useful for a non-chemist who is just trying to mix up some developer.

There it is, in a nutshell.
You say 1:9 = 10
I say 1:9 = 9

You say 1 + 9 = 10
Me too.


We don't need no damned ":" anyway.

Neal:
" However, a dilution of 1 part of "A" with 1 part of "B" still gives you 2 parts."

You are using the word WITH as in AND (Plus), this too I agree with. IF you were going to say dilute 1 part A to 2 parts I would say you will have one part 100% diluted and it would be written 1:2.

Like the man said, it is not so useful for a non-chemist who is just trying to mix up some developer

 

[Neal]

Hi Bruce,

I see we agree that how the instructions are written are key.

I must also thank you for sending me back to reinforce my old algebra skills. A ratio such as 1:2:7 (and so on) is legitimate and is called a "continued ratio". A formula of multiple parts can indeed be described using a continued ratio. Of course, the term ratio does, as you clearly pointed out, refer only to the two items operated on by the ":".

Neal Wydra

 

[Bruce Osgood]

Hi Bruce,

I see we agree that how the instructions are written are key.

I must also thank you for sending me back to reinforce my old algebra skills. A ratio such as 1:2:7 (and so on) is legitimate and is called a "continued ratio". A formula of multiple parts can indeed be described using a continued ratio. Of course, the term ratio does, as you clearly pointed out, refer only to the two items operated on by the ":".

Neal Wydra

I understand what you are saying about a "continued ratio". But when a photo chemist such as Sand King writes the working solution is to be used 1:1:100, do you consider that a total of 102 or 100? I interpeted that to mean 1 + 1 to 100. I realize 100 versus 102 is not significant and perhpas we're picking nits here.

By the way; I know exactly how many angles can sit on the head of a pin, and I'm not going to tell.