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# Thread: Help for the Math-Impaired

1. ## Help for the Math-Impaired

I was setting up a spreadsheet and this isn't a toughie, but I was feeling insecure about my factors. I wanted to figure (both directions) for 1:50 and 1:100 concentrates.....what would the 500ml test batch conversion factors be. I'm speaking of mixing up 500ml working solutions to tweak formulas that will later be made into concentrates? Also, going the other direction, if I want to tweak a known concentrate what is the conversion factor to the 500ml. I'm feeling like I'm looking at this in some way that is making it more complicated than it is as one can scribble this out on paper readily enough but I was having trouble simplifying for a single spreadsheet factor.

2. 1+50 -> 9.8 concentrate + 491.2 water but I suggest using 10 ml of concnetrate + 500 water = 510 ml

1+100 -> 4.95 concnetrate + 495.05 water --> 5 concentrate + 500 water

3. 1:50 is the same as 1+49, so that makes 10ml concentrate to 490ml water.

1:100 = 1+99 : 5ml concentrate and 495ml water = 500ml finished developer.

The difference between 1+x and 1:x has been discussed in depth here before. It is no big deal at these concentrations, but try 1:2 and 1+2 and it makes a BIG difference!

4. Originally Posted by Ole
1:50 is the same as 1+49, so that makes 10ml concentrate to 490ml water.

1:100 = 1+99 : 5ml concentrate and 495ml water = 500ml finished developer.

The difference between 1+x and 1:x has been discussed in depth here before. It is no big deal at these concentrations, but try 1:2 and 1+2 and it makes a BIG difference!

but, 1:1 == 1+1.

5. Originally Posted by GaussianNoise
but, 1:1 == 1+1.
NO!!!!!

1:1 = 1+0, no water added!!!

Some manufacturers insist on writing 1:1 when they mean 1+1. We should not believe that this is correct, but try to find out what they really mean. 1+1 is unambiguous, 1:1 is (sadly) ambiguous.

6. What about 1:2:100 My god two colons? This was on the Unblinking Eye web site.

7. 1 part of solution A, 2 parts of solution B and 100 parts of solution C.

8. Originally Posted by hortense
What about 1:2:100 My god two colons? This was on the Unblinking Eye web site.
It would have been nice if someone had replacd those colons with "+"es.

1+2+100, or even 1+2+97.

9. Originally Posted by Ole
Some manufacturers insist on writing 1:1 when they mean 1+1.

including, I believe, the BIG one in the yellow box. to wit...
• D-76 (1:1)
• HC-110(b) == HC-110(1:31)
• X-tol (1:3)
• etc...

I heartily agree with you Ole but the 800 pound gorilla says otherwise....

10. craigclu,

once you get the impression that someone made an acceptable explanation to the 1+x and 1:x solutions, just buy a beaker and put several markings on it for the amount of water PLUS x amount of developer (or watherever).
I've got one beaker with marks for the amount of water used to develop 1 135 film, 1 120 film, 2 ... and the amount of Rodinal to add to the water in dillutions of 1+25 and 1+50 (I tend to use the latter mostly).

I hope this is clear to you as English is not my mother tongue.

G

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