File photos
By Marcia Y. Kinter
Many professionals in the sign industry work with ultraviolet-curable (UV-curable) inks and coatings in wide-format printing processes, but may not know or think about the associated health and safety risks. It is important to take certain precautions, not only with UV-curable materials, but also with the UV lamps used to cure them.
Ink ingredients
All inks contain both pigments to provide colour and resins to ensure they are flexible and can adhere to substrates. They also contain other additives to help them perform effectively.
In solvent-based ink systems, for example, the solvent acts as a carrier for all of the other ink ingredients and provides the proper viscosity. Once the solvent carries the ink to the substrate, it is no longer needed and evaporates.
In UV-curing systems, on the other hand, solvents are replaced by monomers. These are chemicals with a very simple molecular structure. Monomers can combine to form polymers.
UV-curable inks and coatings also contain photoinitiators. As soon as they reach the substrate, they are exposed to light from a UV lamp. The photointiators then begin a chain reaction of bonding between the monomers and the resin. This process continues until all of the molecules are cross-linked and polymerized, at which point the ink is fully cured, becoming a dry solid.
UV-curable inks are commonly used in both screenprinting (above) and digital printing systems (right).
Health hazards
Many printing professionals are already aware of the hazards associated with solvent-based inks, including dry, irritated skin and respiratory irritation. Further, some solvents are carcinogenic.
While UV-curable materials do not contain conventional solvents and have no chronic, long-term health effects, they can still pose acute hazards. Before they are cured, they can slightly or severely irritate the skin and eyes.
The skin irritation is the same condition that results from touching poison ivy or poison oak, causing a red, itchy, weepy reaction at the point of contact. For some people, this reaction happens within an hour or two. For others, it can take up to two days to show up.
If skin contacts UV materials, it should be washed immediately with mild soap and cool to tepid water for 15 minutes. Solvents should never be used to wash skin.
It is best not to wear jewellery at work, but any worn during contact with UV materials should be taken off while washing, to ensure no contaminants remain trapped underneath. Similarly, any clothing and shoes contaminated with the materials must be removed, as they will otherwise continue to contact the skin, eventually causing a reaction. Contaminated clothing should not be cleaned at home with other, non-contaminated clothes.
If a UV-curable material comes into contact with the eyes, they should be washed at an emergency station and flushed with cool to tepid running water for 15 minutes. Contact lenses, if worn, should be removed immediately, as they can trap contaminants against the eyes. And if any irritation or ‘gritty’ feeling remains after flushing, it is worth visiting a doctor.
