Are cobalt blue containers okay for storing Procion dyes?

Name: Deana

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Country or region: USA (Austin, TX)

Message: Hi Paula,
I could use your advice and input on something. I bought some bulk dyes from Standard and I need to package them into smaller containers for student kits. I am debating between amber plastic jars and cobalt. I know amber provides the widest protection from light, but I can't find what wavelengths cobalt protects from.

How much protection do Procion dyes need from light? I've always been more concerned about moisture and air than light, but I also keep my powdered dyes in a dark space, so it hasn't been an issue. Since these jars will be going to students, I want to give them a good start. But I want the packaging to be attractive, too.

I agree with you that moisture (and the air that carries it) are bigger issues for dye longevity than indoor light. High temperature is also an issue, if it's extreme.

A very good dye supplier, PRO Chemical & Dye, sells Procion MX type dyes in colorless translucent jars. I have not had trouble with ProChem dyes spoiling faster than dyes from other suppliers. However, I usually store my jars of dye in a cardboard box, which does provide protection against light. I think your students' dyes won't be expected to last more than a few months, so there probably won't be a problem as long as they don't store them in direct sunlight. Cobalt-colored plastic would be no worse than unpigmented plastic, so I think the cobalt should be good enough. It certainly is attractive, though it can be more expensive.

Thinking about issues likely to arise with dyes handed out to students: it's important that your students not leave fiber reactive dyes in a car with closed windows on a hot sunny day, because the temperature can easily get high enough to destroy the dyes' reactivity in a single day. You may as well put a label on the jars, or on the package you put the jars into, saying something like "Store at room temperature, out of direct sunlight; do not leave in a hot car."

Cobalt blue glass blocks visible light between 490 and 670 nanometers, and transmits up to 75% of light in the blue and extreme red parts of the spectrum. It blocks the entire middle part of the visible spectrum, including green, yellow, orange, and orangish-red. Amber glass (which seems to me to be dark brown rather than amber in color) transmits about 20% of visible light above 580 nanometers. It blocks most light below 550 nanometers, and essentially all light below 500 nanometers. I don't know how cobalt and amber plastic compare to cobalt and amber glass, in their light absorbance; many plastics transmit more ultraviolet light than plain clear glass does.

Cobalt glass is inferior to amber glass when UV protection is needed, which is why brown bottles protect beer from skunkiness (caused by the effects of ultraviolet light on hops) better than blue ones do. For dyes, protection against UV light is often not as important as protecting against visible light, since the energy the dyes absorb from visible light can damage the dye molecules. Here's a chart showing which wavelengths a number of different Procion MX type dyes absorb (I must have gotten the data for this chart from Olli Niemitalo):

Procion mx dyes spectra

Some of the dyes, such as Turquoise MX-G, have a significant amount of absorbance in the ultraviolet range, which may make them more susceptible to damage from ultraviolet light. It looks as though the red dyes are likely to be well protected by a cobalt blue container.

You're probably already aware of how important it is to avoid breathing dye powder while you are repackaging your dyes. Make sure that your dust mask fits well enough that you don't breathe through gaps at the sides where the mask meets your face. Temporarily turn off fans or air conditioning that create a draft on your work area. Consider cutting holes for your hands in a cardboard box to make a dye mixing box (cover the top with plastic wrap so you can see what you're doing). Remove all food items and food preparation materials from the room, and cover all countertops and tables with plastic or a thick layer of newspapers. It's surprising how easily and quickly a few particles of dye will fly across the room to light on surfaces where you don't want them.

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Are cobalt blue containers okay for storing Procion dyes?

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