HC 110 dilution explanation

I apologise if someone else has asked these questions, they seem basic questions but I have not found clear answers yet.

Why the odd ratios? I can see 1+15 and 1+31 us measurement system 16oz to a pint etc, and assume that the 1+19, 1+39, and 1+79 could work with the UK measures ie 20oz pint 40oz quart etc but where does 1+47, 1+63 come in?

Is there a method of determining the development time from the strength of the solution by comparison to a known strength? ie does a 1+31 solution require a doubling of development time when compared to 1+16?

Does increasing the development time by reducing the strength of the solution assist with finer grain development?

AS a matter of interest can the same dilution tricks be applied to other developers such as Ilfotec DD-X?

I have read Covington's web site but this does not completely explain, particularly for dilutions E and F where the changes in dilution equate approximately to the change in development time, but G does not by a long way.

Grateful of any assistance

This is unrelated to the measurement system, because there is little chance that the quantity that you need is exactly, e.g., one pint. Assume you go for 1+47 dilution, and make life easy using a decimal system Assume you develop 35mm in a Paterson tank: you need 290ml; that means 290/48=6.041ml (round up to 6.0!!!) of concentrate, and water to make 290ml. Pay attention to the minimum amount of concentrate (stated to be 6ml) to develop one film.

Is there a method of determining the development time from the strength of the solution by comparison to a known strength? ie does a 1+31 solution require a doubling of development time when compared to 1+16?

Click to expand...

That's a good first approximation. Beyond that, it's personal calibration: agitation method, the error of your thermometer, etc.

I found the system annoying and don't use it. I measure HC-110 the same way I do Rodinal- 1:100, 1:50, 1:25. I will look at the Massive Development chart-
http://www.digitaltruth.com/devchart.php
and see what is recommended for a new film. I will then have to go look up what B and E and whatever else translate to once again because I never remember which is the 1:47 and the 1:31 and such. This gives me a starting point- 1:50 and 1:47 are close enough, etc. Then I work out what actually works for my process in tests.

Why not

Why not have odd ratios? If that is how much juice you need, then it is. Do you refuse to take photos if there is an odd number of folks in the frame of your camera? Do you not take photos on odd-numbered days? Odd.

The ratios are odd because HC110 was not designed to be diluted directly from concentrate.

It was designed to mix to a stock solution and then be further diluted from there. I don't know of anyone who actually uses it this way anymore...

When Kodak first began marketing HC-110 it was sold almost exclusively to BW photofinishers who used automated developing equipment. Since many of these companies used D-76 or DK-50 Kodak recommended dilutions that used the same development times for HC-110. Therefore the companies did not need to adjust their equipment. Just use the right HC-110 dilution and continue on as you did before.

For home use Kodak recommended making a stock solution which was then further diluted for use. Kodak's reasoning was that the concentrate was thick and syrupy and hard to measure. Today most people dilute the concentrate directly ignoring the various dilutions. For example I dilute 1+49 since it is convent for my size tanks using dilution E times.

Kodak recommends that for any dilution there must be a minimum of 6 ml of concentrate for each roll of film (or 80 in2 any format). However many people reduce this to 5 ml per roll without ill effect. So pick a dilution and use the times at the Covington site.

With this developer, development time is roughly proportional to dilution. Thus:

Dilution D Develop 25% longer than with Dilution B
Dilution E Develop 50% longer than with Dilution B
Dilution F Develop 2.5 times as long as with Dilution B

It appears that dilution B is the most common one used.