Question about mold

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Posted By: davidcycleback

I happen to be finishing a short book on ultraviolet light and if anyone is wishing to buy a light, the ultimate check is when the seller lists the wavelength of the light.

Germicidal lights (the ones that kills mold, aka UVC, aka shortwave UV) is 254 nanometers (nm). Germicidal light is used to decontaminate public air, water and sewage, clean air and surfaces in science labs and hospitals, irradiate milk, etc. While one has to take safety precautions with UVS, a positive is when the light is turned off, it's completely gone-- like when you turn off a light in your room, it's dark. This means, unlike toxic chemicals, it's 'green,' with no aftereffects to the environment, ozone, toxic residue down the sink or fumes lingering in the air, etc.

Blacklight (aka UVA, aka longwave, the kind we use to check for fake baseball cards) is normally 380s-390s, but can anywhere from 320 to 400nm.

The wavelenth is sometimes listed in Anstron (A), which is a simple decimal point conversion, as an Angstrom is 1/10th of a nanometer.

1 nanometer = 10 Angstroms
1 Angstrom = 0.1 nanometer

For perspective, the average human hair is 30,000 nanometers thick.

Germicidal light works because 254nm is the wavelength that damages the DNA of mold, viruses, anthrax, flu, etc, sterilizing the individual organisms (they can't have anymore kids).

As earlier noted, the practical shortcoming of germicidal light is that it only works on what it touches. It works sterilizes surfaces, air and water, but can't penetrate many materials. This may be why a light bleach solution may be best for cardboard. Of course, a T206 is thin for cardboard and mildly translucent, so that's where the question comes in. I can tell you that many of those 'ultra clean' science labs use germicidal light in conjuntion with other cleaning methods, due the limits of what light reaches and pentrates.

There is even much shorter ultraviolet light that is used and studied in advanced science. Some space rockets and stations have telescopes that detect very short uv light and astronomers use them to study stars and planets. For example, they can determine what chemicals are in a star due to the wavelengths of the light. They can also determine the age of a star by its light. This study must be done in space, as earth's atmosphere blocks much light. There is lso uv that is so short that it can't penetrate air and can only used on earth in vacuums.