Which coating inside old dev cans?

[The Ghost]

I've mixed some Microdol-X from a can. The code embossed on the top of the can reads "U7502" so I'm assuming it was manufactured in 1975; 51 years ago. As you can see here, the powder was 100% free-flowing, with ZERO brown to be found.

I'm in awe. I previously mixed a can of D-19 which had minor browning but is still kicking 1 year after mixing, but being D-19 it just made sense. (Great underrated developer, D-19, for Kentmere 400 and Foma 400, might I add)

But my main question is; does anyone know what specific coating Kodak used inside of these cans to impart such incredible keeping properties to their developers? Was there a specific process they employed to help like a nitrogen atmosphere or anything? Asking for a friend*. In any case, I'm super excited to try original Microdol-X (50 years old!!) with recently shot FP4+ for the #FP4party.


* I am in fact asking for myself, out of curiosity and possible future endeavors in film chemical R&D, manufacturing and packaging.

 

[MarkS]

That looks like a very late production can. Is it cardboard with a foil liner? Kodak had stopped offering chemistry in cans by 1975.
I was at the very beginning of my photography around then, but remember the metal cans. They were replaced by foil packages at that time, at around the same time EK discontinued the aluminum 35mm film cans and went to the plastic ones used since. I wouldn't assume that the code stamped in the lid has an obvious meaning.
I would expect that EK used canning methods similar to that which the food industry used.

 

[The Ghost]

Is it cardboard with a foil liner?

Nope, it's all-metal!
I assume that the manufacturing code *has* some kind of meaning; as to if my interpretation is correct, that, I'll possibly never know...

In terms of canning, though, I'm asking because I know different coatings were used depending on industry since back then they canned motor oil, cleaning products, and other wild stuff.

 

[mshchem]

Yep, steel cans, pretty sure it's some sort of epoxy coating. I'm not a package expert, pretty sure these are all pre-painted metal, (before it gets to EK) I've got cans that are 70 years old, powder is perfect, better than what we get in some cases today.

NEVER TRY THE PULL TAB ALUMINUM TOP CANS! Marketing must have had too much say for a couple years. Powder looks like tar in these cans.

 

[mshchem]

 

[ags2mikon]

Lovely picture there my friend.

 

[The Ghost]

View attachment 421386

*u* Whoaaaaaa! Beautiful!!
DK-60a, Selectol, Dektol, Microdol to the right? And is there anything special about these ethol paper devs, other than the incredible can design?

Cheers from up here in Canada

 

[The Ghost]

Powder looks like tar in these cans.

Thanks for the insights! And if I ever go the can route I'll make sure to avoid tabbed cans.

 

[mshchem]

*u* Whoaaaaaa! Beautiful!!
DK-60a, Selectol, Dektol, Microdol to the right? And is there anything special about these ethol paper devs, other than the incredible can design?

Cheers from up here in Canada

I've been trying to get into Canada for years Too old and not enough money ethol LPD was the bomb! Back in the day, when it came in steel cans. Others here can comment, different developing agent than Dektol, I use Bromophen today. Once mixed into stock divide it into absolutely full litre bottles. Stock keeps forever, use deionized water.

I have several of the 5 gallon Dektol, that's the definition of insanity!!!!

Cheers from Iowa, a weird place right now

 

[Yezishu]

To the best of my knowledge, the preservation relies on the airtightness of the metal cans. It the cans are well-sealed and the exterior coating prevents corrosion, the small amount of oxygen in the can will be rapidly depleted.

The coating is likely an epoxy-phenolic resin—such as Wolverine's ChemShield 1680. These coatings do not play the decisive role in preservation; they prevent the chemicals from contacting with the metal, thereby averting corrosion. A simple HDPE bag often serves much the same purpose.

A modern soft can utilizes aluminum-plastic composite films. These films feature an airtight aluminum foil layer backed by a plastic inner flim; they may not offer the same longterm preservation as metal cans, they are good enough in the product's shelf life.

 

[The Ghost]

The coating is likely an epoxy-phenolic resin

Yeah I figure they had epoxy in the 60's and 70's...