# Dummies Guide on developer dilution?

Discussion in 'Film and Processing' started by smithmaestro, Jun 30, 2012.

1. So I have had this question ever since I nearly messed up my films. For example, D76 1:9 or HC110 1:7. I have no idea what to do or how to do it.
Here's what I was thinking before saving my self from messing it up:
1: Measured amount of liquid the container holds
2: Did math to find out how much water I need to dilute it
2.5: If it's 500ml, then i guess it's like 1/9*500?
3: Try it out and probably mess up
4: Cry and just put stock solution
5: Works and... still not too impressed.
So I guess it's time to man up and learn how to dilute and this is the place to do it, I guess.

2. Bryan,
Ratios can be confusing. 1:9 or 1 to 9 is not the same as the fraction 1/9. Basically it means add 1 part to 9 parts, which would explain why my first photo professor always wrote the mixing ratios with a (+) instead of a ).
1:9 means a 10 part solution where 1 part of it is one thing and the remaining 9 parts another.
For D76 it would be 1 part stock, 9 parts water.
So 500ml working solution of D76 mixed 1:9 would be 50ml stock and 450ml water.
The way I figure it out is to take the desired amount of working solution, divide it by the total of the two numbers in the ratio and then multiply that by each individual number.
For D76:
500/(1 + 9) =
500/10 = 50
50(1:9) =
50:450 =
50ml stock + 450ml water =
500ml working solution
For HC110:
500/(1 + 7) =
500/8 = 62.5.
62.5(1:7) =
62.5:437.5 =
62.5ml stock + 437.5ml water =
500ml working solution
Hope I didn't make things worse,
Raul

3. I will often round the amount of working solution up a bit to make the numbers even. For instance, if I'm developing 1 roll of film in a Nikor Q08 (8 ounce) tank, using Ilford Ilfotec DD-X 1+4, instead of trying to divide 8 by 5 (yuck), I'll make 250 mL of developer (which is a bit too much), but is very nicely divisible by 5. So that's 50 mL of liquid concentrate, and 200 mL of water.
Accuracy is important, particularly for uneven ratios. Use graduated cylinders of the appropriate size, so that the amount you're measuring is at least a third of the capacity of the cylinder. For HC-110 syrup, use a positive displacement method such as a children's dosing syringe, since you need the same percentage of accuracy on measuring the small amount of syrup.

4. OK your dilution is 1:7 and you need 500m.
Discoverer the total number by adding the two values of the ratio together thus 1 + 7 = 8
There will be 8 parts total.
How large is a part? Answer 500 ÷ 8 = 62.5ml
The dilution is 1 part developer = 62.5ml
Water = 7 parts thus 62.5 X 7 = 437.5mm
Answer 62.5ml developer diluted with 437.5ml water.
Let's do this again for a ratio of 1:9
To make 500ml at 1:9 ratio
Total parts = 1 + 9 =10
How big is a part? 500 ÷ 10 = 50mm (part size)
Developer = 1 part = 50ml
Water = 9 parts = 50 X 9 = 450ml
Try 1:16 (1 part developer diluted 16 parts water and make 500ml.
Total parts = 17
Developer = 500 ÷ 17 = 29.5ml (this amount of developer OK to round)
Water = 16 X 29.5 = 472ml

5. there are other ways to make what you need safely
there is an often critisized " spoonup.pdf
that uses spoons to measure powdered chemicals
many say this leads to error.
the other AWFUL confusion is making a STOCK solution of HC-110
that is for a big lab. and the "stock will oxidize and get dumped.
better to go to the covington hc-110 page and mix small amounts of syrup
directly from the bottle. use once and dispose.
what is this D-76 9:1 busines? d-76 is used stock 1:L 2:L and sometimes even 3:1
Typical liquid developers other than hc-110 might be used at 9:1
something like Rodinal is used 25 50 or even 100 :1
Rodinal is best for slower films.
also remember a certain amount of developer is needed to develop a roll of film.
if it is TOO dilute and there is too little developer
the results will be useless.

6. instead of trying to divide 8 by 5 (yuck)​

Not yuck, easy 8/5 = 16/10.

7. Yes, but there's no 1.6 ounce mark on my graduated cylinder -- the fluid once scale is by half-ounces. Eyeballing it is not the best idea. I can measure more accurately by making 250 mL, and that's the other reason I do it that way.

8. I will often round the amount of working solution up a bit to make the numbers even​
Same here, for pretty much the same reasons.
what is this D-76 9:1 busines? d-76 is used stock 1:L 2:L and sometimes even 3:1​
Good catch. D76 is used straight or 1:1. I have used Dektol 1:9 though.
I was going to edit my previous post to reflect the recommended D76 solution, but I guess I can't change an old post. Hope the OP reads all the responses.

9. If you want to make 500ml of D-76, diluted 1:9, measure out 56 ml of stock D-76 (=500/9) and dilute it with water to 500 ml. This is so routine, pharmacists have a term for it, "Q.S." That means something in Latin that I have forgotten, translated to "dilute to volume".
Technically, if you mix two solutions of different concentration, the final volume will be less than the sum of the components. The difference is small in this case, but measureable. That's why dilutions are always specified to a final volume or weight. I could explain why, but that's for another time and venue.
In order to reduce measurement errors, you would measure the D-76 in a 100 ml graduated cylinder, pour it into a 500 ml (marked) container, and rinse the 100 ml cylinder two or three times with the diluent to capture the concentrate sticking to the sides. When using a graduated cylinder, the liquid will form a curved surface, called a "meniscus." Measure to the lowest part of the miniscus.
The only D-76 developer I've used came as a powder, which was dissolved to make a certain volume of solution, such as 1 gallon. Rather than reusing that solution, I would dilute it 1:1, use it once and toss it afterwards. The processing time was adjusted to about 50% longer than normal, to something like 6 minutes. The dilution had two positive effects - a longer development time makes errors in timing less signficant (e.g., fill and drain times before rinsing), and the diluted developer results in lower contrast, which was good for subsequent publishing (shadow detail). The unused stock solution would last 2 or 3 times as long as recycled developer.

10. Edward you made a mistake!
If a 1:9 mix ratio is desired, you first we add together the left and right digits of the ratio to obtain the total number of parts. In this case 1 +9 =10. Thus 10 parts will be required to make the whole. If we are to make 500ml total we divide 500 by 10 to calculate the volume of 1 part (the developer part). Since we desire a total of 500ml, we divide 500 by 10 thus 500 ÷ 10 =50. This tells us the developer portion shall be 50ml. The water portion will be 9 parts thus 50 x 9 = 450ml. In other words mixing 50ml of developer with 450ml of water makes a 1:9 ratio solution.
You error was to divide 500ml by 9 = 55.6ml (56ml rounded). If you use this value, the amount of water now needed to make 500ml total is 500 - 56 = 444ml. Using this method the ratio is 444 ÷ 56 = 7.93. In other words, you formulated at 1:7.9 ratio not 1:9.
Q.S. = Quantum Sufficit -- Latin translated "top off to desired volume".