Help me understand ratios

[jamesj]

This may sound like a stupid question, but I am trying to get the hang of this.

I finally have decided to start develop my own rolls and I get the process But for the life of me cannot understand the ratios. I understand d76 is 1+1 so that would be equal parts water and developer. I have a 2 reel Paterson System 4 canister. everywhere I read they said to use 600 for the canister to make sure it is all submerged in developer. which makes sense to me.

The thing is I have some Rodinal and the ratio is 1+25 or 1+50 and so forth. But how do you figure out how much to use I can't figure it out. I found this in another thread but how does one come up with these numbers.

1. 6ml Rodinal concentrate + water to raise the measure to 300ml (one roll)

2. 12ml Rodinal concentrate + water to raise the measture to 600ml (two rolls)

 

[kokoshawnuff]

300/50=6
600/50=12

 

[jamesj]

ok that makes sense. Does it work the same at 1+25???

 

[*chris]

ok that makes sense. Does it work the same at 1+25???

pretty sure but don't quote me because i was asking how to actually mix it😛... what camera and film are you going to be using?

 

[jamesj]

my m6 and I was going to try acros 100

 

[*chris]

my m6 and I was going to try acros 100

nice you have the camera i want haha. i plan to get an m6 classic in the future🙄

 

[kokoshawnuff]

Yes or with 1+100, 1+75, 1+7, etc.

If you're new to the tank make sure to measure out the capacity (with a water prewash or something) the full container with film inside, because the numbers they give can be misleading one way or the other. You will either not make enough and the development will be uneven, or you'll make too much and you'll waste chemicals.

 

[andersju]

1+25 just means one part developer to 25 parts water in whatever unit of measurement. Take the total amount of liquid needed divided by the ratio and you'll get the amount of developer. With those plastic reels each film needs 300 ml, so for 1+25: 300 / (1+25) = 300 / 26 = ~11.5 ml Rodinal. Or 600 / 26 for two rolls.

So 1+50 is actually ~5.88 ml for one roll, ~11.77 ml for two... but rounding them to 6 and 12 (in other words, diluting it 1+49) makes it easier to work with and doesn't really matter - the most important thing is being consistent.

 

[V-12]

Ilford dilutions make it easier, 1+4 is one part chemical plus four parts water, so 1 plus 4 = 5 and you simply divide the total amount you need by 5 to find the amount of developer. Same for 1+9 (10), or 1+14 (15)etc.

 

[rpsawin]

If you have an IPod, iPhone or iPad you can download the "Massive Development Chart" app and it has mixing instructions included. I use it all the time. It's a great tool!

 

[ruby.monkey]

Ilford dilutions make it easier, 1+4 is one part chemical plus four parts water, so 1 plus 4 = 5 and you simply divide the total amount you need by 5 to find the amount of developer. Same for 1+9 (10), or 1+14 (15)etc.

Indeed. If you're after a total volume V of working solution, the volume of developer you need is:

Ratio A:B -> (A/B) * V
Ratio A+B -> [A/(A+B)] * V

 

[andersju]

Indeed. If you're after a total volume V of working solution, the volume of developer you need is:

Ratio A:B -> (A/B) * V
Ratio A+B -> [A/(A+B)] * V

It has to be noted that a lot of people take : and + to mean the same thing, which might cause some confusion. See for example Consensus on the notation of dilutions on APUG 🙂

 

[jamesj]

Ok this is making a little more sense everyone, thanx for the help.

Hopefully Ill get it right.

- james