Testing paper developer using refractometer

I have a salinity refractometer I use for saltwater testing. I tried it on my developer and it reads 1.027 were the developer spec sheets says 1.024. I have seen no chage in SG since I mixed a gallon of 110C about a month ago. Do you think it's still good even though SG reads same as freshly mixed? I have only used it less than six times for about two hours each time.

Which print developer are you referring to? I don't recognize "110C".
And I don't know whether a change in specific gravity will tell you anything about the health of print developer.
12 hours of use means a lot of opportunity for oxidation.

hi sruddy
sounds like you are over complicating things
no need to measure the SG.
what you can do is put a coin on a small scrap of paper
turn the lights on and develop the paper to the mfr's reccomendations
maybe 1 min RC 2 or 3 mins fb ... and see if you get blacks
if you don't have good blacks mix fresh ...
wet plate you need a SG reading not regular ol' DO paper

have fun!
john

MattKing said:

Which print developer are you referring to? I don't recognize "110C".
And I don't know whether a change in specific gravity will tell you anything about the health of print developer.
12 hours of use means a lot of opportunity for oxidation.

Click to expand...

Man, sorry that's the film developer I use, and it's actually HC-110. For paper I'm using ILFORD Multigrade and I just picked up spme ILFORD Harman Warm Tone.

jnanian said:

hi sruddy
sounds like you are over complicating things
no need to measure the SG.
what you can do is put a coin on a small scrap of paper
turn the lights on and develop the paper to the mfr's reccomendations
maybe 1 min RC 2 or 3 mins fb ... and see if you get blacks
if you don't have good blacks mix fresh ...
wet plate you need a SG reading not regular ol' DO paper

have fun!
john

Click to expand...

Actually I thought if I could reply on SG readings it would be quicker and easier. Maybe this isn't the case. I'll try your method but I would first need to know the test papers maximum black. I'll go ahead and make test sheets for maximin black as a reference. I could purchase a densitometer but that would definitly be a bit ecessive, I think my eyes will work well enough.

In principle the refractometer approach should not work. As an analytic device a refractometer is a convenient way of monitoring the concentration of binary solutions; one solute, one solvent. A paper developer is complex mixture = anything but a binary solution.
On the other hand if you can establish a reliable correlation between refractive index (in whatever units) and developer activity then it won't be the first time the impossible became possible.

sruddy said:

Actually I thought if I could reply on SG readings it would be quicker and easier. Maybe this isn't the case.

Click to expand...

Hi, I've read about a zillion specific gravities on photo chem samples, but they won't be much help in your situation. For the most part, a sp gr reading tells you the general weigh of chemicals dissolved in water. So if you mixed a developer wrong - perhaps the wrong amount of water - there would be a change in the sp gr. But for you, since you are mixing it yourself, it's easier to just double check that the amounts are correct. Now, if you sometimes use different dilutions of HC-110 and forgot which one it was, then a sp gr could help figure this out.

With respect to determining if a developer is still good, sp gr is of little use. For example, you could destroy a developer by bubbling air through it (this would oxidize the developing agent, ruining the developer), yet the amount of dissolved chemicals, and thus the sp gr, remain essentially the same.

By far the best way to check the condition of a developer is to develop a test sample of film or paper in it. In commercial work you'd want to have a densitometer and some sort of known-good reference, but for your own work, your eyes are probably just fine.