Mixing solids with liquids to make a percentage solution.

Kirk Keyes · May 27, 2011

Photo Engineer said:
There are three ways to specify percentage of solution. They are w/v, w/w and v/v where w = weight and v = volume.

There's actually 4 ways - you missed v/w.

Not that it get's used much, but it's one more option to confuse the situation!

Megrez · May 27, 2011

holmburgers said:
Hahaha.... it just goes to show you that nothing in photographic chemistry as easy as you want it to be. But if you're at least consistent in what you do with a % solution, you can adjust it depending your results.

I would assume the OP is making a simple fix solution (?) or a stock solution for some purpose, in which case it seems like he didn't know the that a gram of water will have a mL of volume, or a mL of water will weigh 1 gram. After I learned this "dumbed down" rule, I closed that chapter in my brian and put it back on the shelf.

You are quite right, I didn't realise that a gram of water is approximately equal to a Ml of dry power. But now I do. For information, I am making fixer for salt prints, using the recipe on the Alternative Photography website: http://tinyurl.com/3hsutkn.

I must admit, reading through your replies I was concerned, at one stage, that I was concerned that I may have sparked WWIII. Thank fully not!

Thank you everyone for taking the time and trouble to reply. I am feeling less naive now!

Photo Engineer · May 27, 2011

One gram of water is NOT equal to a ml of dry powder. Powders can very substantially from that value due to the density of the powder. Even with liquids this varies. For example, 1 ml of mercury = ~ 13 grams! So do NOT measure solids by volume.

PE

wogster · May 27, 2011

holmburgers said:
I just find it amusing that the OP asks how to make a peanut butter and jelly sandwich and all of a sudden we're telling him about George Washington Carver's childhood, the climate conditions necessary for raspberries and the finest conditions for yeast cultivation.

Not that there's anything wrong with that.... it's just funny.

It's an interesting discussion nonetheless

I always heard this as someone asking what time it is, and the reply explaining how to construct a watch....

2F/2F · May 27, 2011

An "x-percent solution" is x grams in 100 mL of final solution volume. Scale that up to a liter, and you get 10 times x grams in 1000 mL. So, if x = 10 percent, you use 100 g of stuff to make 1 L of solution.

Look at how developer instructions usually instruct you to make a liter of solution. You start with less than the desired final volume, mix the powders in, then add "water to make" 1L. If you mix everything in to 1 L of water, you end up with too much solution, and it is at the wrong dilution.

Mixing solids with liquids to make a percentage solution.

Kirk Keyes

Megrez

Photo Engineer

wogster

2F/2F

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