It is perfectly known that the UV curable inks and coatings are highly sensitive to the sunlight and must be protected from the sunlight. Pretty much every dealer and printshop pay attention to the lighting conditions of their warehouse and to the storing conditions of their UV curable material. Good conditions of storage mean, that the UV sensitive materials are stored in dark and dry place, away from excessive heat sources and protected from freezing.
I have seen many situations, where the press (coating) rooms conditions are easily overlooked. Shading (painting or covering) the Windows, to block the penetrating sunlight is a good practice and highly recommended. It is surprising, that there are still some print shops available out there, where the windows are not covered, by the belief, that the sunlight through windows on the other side of the factory won’t reach the off-line coating machine. That is wrong. With some small and practically free of charge precautions, you may ease the cleaning process of your rollers and blades.
Another potential threat for your UV sensitive materials in the press room are those strong fluorescent lamps. Even though these lamps emit colder lights from the spectrum, today’s well-developed photoinitiators used in UV curable materials are sensitive to a wide bandwidth of wavelengths. This property is required to ensure the suitability for all different types of UV lamps with different power output. (LED curable UV products are out of the scope of this topic.)
There are few simple, yet very effective precautions to take in the press room, to protect the UV sensitive materials.
- Always keep the packing (jerrycan, bucket, drum…) closed or covered,
- If a proper warehouse room/section is available, store the inventory in the warehouse and only take the necessary amount into the press room,
- If the circulating / returning UV coating is collected in an external bucket/container, make sure that it is also covered (cut a piece of carton to block the day and ceiling lights to penetrate)
- If you have strong lighting above the UV coating unit/section, make sure to cover the rollers where the UV coating is delivered. A wide cut of a cardboard will cost nothing. Easy to produce in-house and very effective in blocking light exposure. This will be helpful especially between shifts, between jobs, during breaks, etc, when the rollers are still wet by the UV coating but staying still. This cover will avoid any possible low level of polymerization on the exposed side of the rollers and blades. This under-cured polymerization (in worst situations) may cause line markings on the substrate, will make the cleaning of the roller difficult, thus possibly damaging the roller or shortening its lifespan.
Have a look around, in your press room and think where you can add some simple protective light shields.