D76 (for high school darkroom)

This is my first year as a high school photography teacher and I am a

little confused about D76 developer. I have only used Sprint before,

but the store didn't have it. I bought the 10 gallon sized container

of D76, thinking that I would be able to mix it in smaller amounts of

a gallon or two at a time, but the directions are only for making 10

gallons. I ckecked Kodak's site and there are different directions

for using a stock solution of D76 or a 1:1 solution. I really don't

know what I should be using. We are using Tri-X film. Can somebody

explain how to make one gallon of D76 solution? I don't mind dumping

it down the drain, I do not plan on re-using or replenishing it.

It is not really recommended to mix only a portion of a large package. This is perfectly ok with liquid concentrates but with powder chemicals, the mix tends to be separated to lighter and denser chemicals in the bag during transportation. So, the Kodak's official instruction would tell you to dissolve the entire bag in 7 to 8 gallons of water and add water to make 10 gallons. That's that, as far as preparing stock solution is concerned.

 

However, if you have a small industrial chemical mixer, you can thoroughly mix the dry chemical again, and split the chemical evenly into 10 portions by weighing (you have to do this by weight). This way, you can prepare 1 gallon stocks 10 times. Again, this is not a part of Kodak instruction, so you should do this at your own risk.

 

Furthermore, if you don't have an industrial dry chemical mixer, it's probably ok to dump the pack into a large container and manually mix for several minutes (watch out for chemical dusts) and follow as above. This shouldn't cause a huge problem with D-76 but again, do it at your own risk!

About all I can add to Ryuji's advice is to have students use only the 1+1 dilution for one shot use. Have 'em discard it after a single use.

 

When I was in school our teacher tried the replenishment method, assigning the task to students. Almost invariably someone would dump fixer in the D-76 and kill it, or get something else wrong which would produce inconsistent results.

 

That's why I switched to HC-110 in school. It's not superior to D-76 - the results are about the same. But I had control over my developer and the little square bottle of concentrate fit neatly into my locker or desk.

To add to the above good comments, using D-76 1:1 provides slightly sharper results than using it undiluted (at the expense of slightly more grain). I personally find the results to be superior this way compared to using it undiluted.

don't be affraid to mix just a portion at a time, I've been doing it for years myself. Surely, your high school's chemistry classroom must have a decent chemical balance

The easiest thing to do is to mix up the whole batch and decant into smaller bottles like gallons or quarts.

Another thing I've heard of people doing is mixing the D-76 in half the amount of water. That's going to require the water be hotter than the recommendation (I found 120 F worked for straight sulfite, it'll be probably be fine for the D-76), because the resulting 200 g/L of sulfite is close to saturation even in the absence of borax, but it does work, and the resulting double strength stock solution, in addition to being a bit easier to store, keeps even better than standard stock. Be sure it's carefully marked as double strength -- not a bad idea to put the corrected dilution requirements on the storage bottles, too. Dilute 1+1 to make standard stock solution for the lab, which can then be diluted 1+1 again for one-shot use -- and meanwhile, the undiluted double stock is happily sitting in its bottles.

I do not know what your experience with b&w photo chems are, but to say "I do not mind dumping it down the drain" concerns me a little. If you are not familiar with what you are working with, please don't dump it down the drain. All chemicals are dangerous, but some are more dangerous than others.

While I don't wish to negate the point Rich is making, there are relatively little health risk associated with most common darkroom chemicals used by beginners.

 

However, you should check your school district's policy on disposal of anything that might be considered hazardous materials. This would have more to do with environmental protection and protection of the water supply than with personal safety. Sad but true: People are seldom the #1 priority where such regulations are concerned.

 

A simple example would be the cleaning materials used by the janitors ... housekeeping ... uhh ... sanitation engineers ...? I'm not sure what the current titles are but it's almost certain that they will have copies of MSDS's (Material Safety Data Sheets) for their cleaning products, most of which will probably be rather harmless compared with products used in the past.

 

You can obtain a copy of the MSDS for each chemical you use in the darkroom. Kodak will probably have it online for D-76, their stop bath, fixer, even Photo-Flo (pretty much a simple surfactant) if you decide to use it to help minimize water spots on negatives.

 

I would suggest that you *don't* make a big deal about these issues with any school authorities until you've gathered the MSDS's and any available information about disposal so that if and when it does become necessary to discuss the issue with school officials they don't panic and decide to peremptorily shut down the darkroom rather than subject the children to the dangers of having fun and learning something.

Just switchs to liquid, that's much easier than all that shitty powder. Makes me wonder why anyone would ever go through the problems of powder, it's not that there no other great developers present.

Powders last a lot longer in storage, that's why. Powders are cheaper, too, something that to a school is a rather important issue.

I use D76 and love it. But for a school, use Hc 110. Both 110 and D76 have two year shelf life unopened.

 

Mixed D76 in full glass containers is good for 6 months. You are going to get oxidation of any partial unused powder if you mix it a bit at a time unless you can find a way to exclude air from the storage of powder.

Pour the D76 powder into a plastic garbage bag... Tie and duct tape the top closed leaving lots of air space above the powder... Weigh the whole mess - later, deduct from the gross weight the weight of the garbage bag and tape, after emptying it.... Put the bag in a cardboard box and tape the lid shut... Then vigorously, but carefully, roll the box over and over to mix the powders... Good project for kids...

Then open box, cut off one bottom corner of the bag, and decant the powder into air tight containers (tupperware from the home ec room?)...

When ready to mix up a gallon of developer weigh out 1/10 of the original powder weight and mix...

 

denny