What chemicals need to be protected from light?

[srs5694]

Hi,

The subject of protecting chemicals from light has popped up as a side issue in several recent threads related to bottles and storage, but the issue of light has not gotten much of an airing. The conventional wisdom, repeated on Web sites and books, is to store photochemicals in opaque bottles to prevent them from being degraded by exposure to light. My question is: How much of an issue is this in reality, and for what classes of products or specific products? For instance, should developers be protected from light but it doesn't matter for fixers? Are developers made with X, Y, and Z light-sensitive but those made with A, B, and C aren't? Are any raw chemicals (phenidone, sodium carbonate, etc.) sensitive to light? Of course, I realize that light exposure isn't all-or-none; I'm just wondering about ordinary levels of room lighting. Even in a darkroom, the lights could be full on for several minutes a day, and that level of exposure could add up over time. The need (or lack of need) to protect against that level of exposure could be important in deciding how to store chemicals -- in opaque vs. clear bottles, in boxes vs. on open shelves, etc.

 

[dancqu]

The conventional wisdom, repeated on Web sites and books,
is to store photochemicals in opaque bottles ...

Likely those who have a good store of light sensitive
photo chemistry could count on one hand the number
of light sensitive chemicals they do have.

Two such chemicals are silver nitrate and potassium
ferricyanide.

CLEAR amber glass Boston Rounds are a standard
for chemical storage. Opaque containers should
NOT be used. Clear glass or plastic allows for
inspection. Dan

 

[kodachrome64]

I am interested in this too, and whether plastic vs. glass actually matters in the real world. I can get plastic and glass bottles for about the same price honestly, but the amber glass bottles are definitely not opaque.

 

[David A. Goldfarb]

Glycin is always sold in opaque packaging.

 

[dancqu]

Glycin is always sold in opaque packaging.

Opaque is likely best for shipping. My amber glass
chemistry storage is cupboard kept. Bottle exposure
to room level lighting is short term. Any dark storage
space should do whatever the container color. If the
chemistry is not light sensitive then where ever.
Clear though for cleanliness. Dan

 

[Photo Engineer]

Potassium Iodide is another as is potassium dichromate. I never heard of pure dry ferricyanide requiring dark storage though.

Usually, dryness is more important than darkness. Along with that comes contamination or contact with air. Keep all bottles tightly closed!

PE

 

[Dave Miller]

I use amber glass screw top bottles simply because I wanted a couple and brought a box full. I also use the plastic bottles that I originally brought neat developer in, some are clear some not.