Topic: a math question + a fix question

[formica]

tonight while developing some bw film, i started to get confused about mixing the chemicals. if you are mixing say 1 to 9 for a total mixture of say 100, the amount of chemicals should be 10.  am i right in that?

and my second question, how do you know when fix is going or has gone bad?

          william

[Pete_R]

tonight while developing some bw film, i started to get confused about mixing the chemicals. if you are mixing say 1 to 9 for a total mixture of say 100, the amount of chemicals should be 10.  am i right in that?

Yes ... 100/(1+9)=10

and my second question, how do you know when fix is going or has gone bad?

I always check the clearing time and when it's twice what it was when it was fresh, it gets chucked. Don't remember where I got that from - too long ago - but I've always used it.

[formica]

and my second question, how do you know when fix is going or has gone bad?

I always check the clearing time and when it's twice what it was when it was fresh, it gets chucked. Don't remember where I got that from - too long ago - but I've always used it.

what do you mean by clearing time, the time printed on the bottle it comes in about how long it should last? and thanks for clearing up my math stupidity.

                 william

[Francois]

Taking note of clearing time will tell you when fixer gets exhausted.
To calculate it, clip the undeveloped leader off a 35mm roll.
Take a small container and fill it with fixer.
Take an eyedropper and put a single drop on the film.
Wait 1 minute. You should see a relatively transparent dot.
Put the leader in the film and start timing.
When you don't see the dot anymore, stop the chronometer.
This is the clearing time.

[Pete_R]

what do you mean by clearing time,

Francois isn't wrong but I don't go to those lengths. I clip the leader off the film and dip it in some fixer and watch it until the film goes clear. It's pretty easy to tell when it happens.

[Francois]

The drop helps in finding what the base density is like... just a bit more precise.

[LT]

and my second question, how do you know when fix is going or has gone bad?

My fixer has gone bad when I finish my session - a bit wasteful I know, but fresh chemicals each time give me peace of mind.

[Francois]

If you want an easy way to "push" your fixer safely, get a small bottle of hypo test.
I have a small bottle I found at a garage sale (the guy was liquidating parts of his lab)... got it for cheap.

[db]

I know my fixer has gone bad when I find cigarette butts and liquor bottles in the darkroom sink next morning..

[outofcontxt]

That fixer isn't just bad, Don, it's just plain wicked!