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A clear way to heaven: Print 21 magazine article

Wednesday, 03 December 2008
By Print21

There’s nothing quite like star-gazing in outback Australia where the clear skies seem to bring the heavenly orbs almost within reach. But, as Steve Smith argues, keeping our skies smog-free isn’t helped by our current guidelines on VOC emissions.

One of my favourite quotations is a rather obscure one you’ve probably never heard. It’s from influential US historian Charles Beard, and he said, "When it’s dark enough, you can see the stars." I like the clever double meaning and encouraging sentiment behind Beard’s simple words.

Earlier this year I was gazing up at the stars in Bundaberg, Queensland; the country night sky is far richer than a smoggy city atmosphere that reflects the masking glow of a couple of million street lights. We’re lucky in the southern hemisphere that we are positioned for a grandstand view of the Milky Way, a cross-section of our galaxy splashed across the middle of the heavens.

Most of us learned when we were primary school age that the planets of our solar system are visible as unblinking points of light, whereas the distant stars twinkle; and we probably even remember the scientific theory behind that sparkling effect. This time, however, I’m not going to launch into an explanation for those who have forgotten.

As I gazed up at the star-spangled vault above this sleepy rural Queensland town, it occurred to me that another reason why stars twinkle is simply because it looks better that way.

The need to know

I write these articles for Print21 in an effort to explain chemistry-related aspects of the printing industry and general science. As a confirmed technical geek, I like to know what makes things work and why they happen. Some of my friends and colleagues have occasionally found this quite annoying, and I can empathise with that view, too. We don’t always need to know the real ‘Why’.

But, of course, in some instances we really do. For example, there’s an environmental issue which is impacted a little by our industry called volatile organic compounds or VOC. A typical volatile (or rapidly evaporating) organic compound is isopropyl alcohol, used in sheetfed printing. Additionally, most blanket and roller washes, flexographic inks, and some fountain solution ingredients are VOC examples. When the gases emanating from these volatile organic compounds evaporate, they react with certain exhaust emissions – for example from cars – and are cooked by sunlight to form smog.

A major component of smog is a super-charged variety of oxygen known as ozone. Ground level ozone where we live – not the ozone layer 10 kilometres above us in the stratosphere – is a major health problem. So, volatile organic compounds, while not necessarily harmful on their own, can lead to the formation of toxic ozone in the air we breathe.

As I wrote in Print21 last year, in the USA the test method for measuring volatile organic compounds is very severe and quite difficult to meet. The European regulations are a little more relaxed and, dare I say, rather more realistic. They look at the internal energy a liquid must have for the vapour to escape from the surface and enter the atmosphere as a gas, where it has to go if it is eventually to form ozone. This energy is expressed as vapour pressure, and it uses the same units you measure when pumping up the tyres on the family car: kilopascals, or kPa.

In Europe, any volatile organic compound (you can replace that phrase with the word ‘solvent’ if it makes you feel better) having a vapour pressure less than 0.01 kPa is not classified as a VOC. To make it even simpler to understand, that equates roughly to a solvent with a flashpoint of about 100°C. That’s pretty high, but not unheard of in blanket and roller washes, or the solvent components in fountain solutions.

Definition of absurdity

Here’s where it gets strange. In Australia, there is an interpretation of volatile organic compounds promulgated by our Federal Government that defines a volatile organic compound as having a vapour pressure greater than 0.27 kPa. That’s right, twenty-seven times higher than the European standard. The National Pollutant Inventory (NPI), part of the Department of the Environment, says that, by their definition, any solvent with a vapour pressure less than 0.27 kPa is not a VOC. That equates to a flashpoint of approximately 40°C, thus including most Class 3 flammable liquids … as non-VOC!

It’s just absurd. The saving grace is that a NPI definition is not a law or even a guideline; it is just a definition, albeit a misguided one. It is time the definition was changed to fit in with present environmental concerns. It has the potential for printers to be using a chemical that, in good faith, they thought was zero VOC but actually won’t be doing much at all to decrease smog and ozone levels.

In this year of the US election, I’ll leave you with another Charles Beard quotation which demonstrates his sense of irony looking back at the history of the USA: "You need only reflect that one of the best ways to get yourself a reputation as a dangerous citizen these days is to go about repeating the very phrases which our founding fathers used in the struggle for independence."

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