UV Printing Safety: Ink, Fumes and UV Light

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UV printing is not a dangerous hobby, but it is a chemical one. The liquid ink is the main issue, not the finished print. If you follow a few rules from the start, you will have no problems later. If you ignore them, you risk an allergy that does not go away again.

Uncured ink: the real risk

UV ink consists largely of acrylates, that is, reactive plastic building blocks, plus photoinitiators and pigments. As long as it is liquid, it can irritate the skin. Above all, though, acrylates can sensitise. That means: after repeated contact, your body develops an allergy. After that, even small amounts are enough to cause eczema, and the allergy as a rule lasts for good.

Safety data sheets typically carry the hazard statement H317 for this: “May cause an allergic skin reaction”. The German statutory accident insurance body BG ETEM (Energie Textil Elektro Medienerzeugnisse) therefore treats UV inks and varnishes as working materials for which skin protection comes first.

Download the safety data sheet (SDS) for every ink, every primer and every cleaning fluid. Reputable retailers and manufacturers provide it. It lists the specific hazards, the recommended protective equipment and notes on disposal. If there is no safety data sheet for an ink, that is a warning sign.

Gloves and skin protection

• Wear nitrile gloves as soon as you handle ink, cartridges, the print head, wipers or the waste container. BG ETEM names nitrile and polychloroprene as suitable materials. Latex and vinyl are not a good choice.
• Change disposable gloves after contact with ink, do not wear the same ones all day.
• Take gloves off correctly, without touching the outside.
• Wash ink on the skin off immediately with soap and water. Do not put solvents or cleaning fluid on the skin, as this tends to let the substances penetrate deeper.
• Wear safety glasses when refilling and cleaning if splashes are possible. If ink gets in your eyes, rinse for a long time with water and have it checked by a doctor.
• Change soiled clothing and wash it separately.

If redness, itching or blisters appear on your hands or forearms, that is a serious sign. Have it checked by a doctor and review how you work.

Ventilation and smell

UV ink smells, especially fresh after printing and during cleaning. Some of the constituents are volatile, and cleaning fluids add to this. Safety data sheets generally require adequate ventilation.

In practice this means:

• Do not run the printer in a bedroom or in a small, unventilated room.
• Ventilate regularly or use extraction or an activated carbon air filter, if the manufacturer offers one.
• No eating or drinking at the printer’s workspace.

Unlike older mercury vapour lamps, modern UV LED lamps produce practically no ozone. The smell comes from the ink.

UV LED: do not look into it

The curing lamp mostly works in the UVA range around 365 to 405 nm and is very intense. UVA is only partly visible to the eye, so the lamp can be stronger than it looks. Looking directly into the lamp can damage the eyes, and longer exposure also irritates the skin.

• Never look into the running lamp, not even briefly.
• Do not bypass covers and safety switches.
• With open machines, wear UV protective glasses as specified by the manufacturer.

Disposal

Uncured ink, ink residues from the waste container, used cleaning fluid and soaked cloths do not belong in the drain or in household waste. Printing ink waste containing hazardous substances is hazardous waste.

• Private: take it to the hazardous waste collection or the recycling centre, well sealed and labelled.
• Commercial: through a specialist waste disposal company.
• Collect soaked cloths in a tightly closing container, as BG ETEM also specifies for print shops.

Some manufacturers recommend fully curing small residues on cloths under UV light. Whether that is enough in your case is stated in the safety data sheet or can be clarified by your local waste advice service. Empty cartridges and bottles always contain residues and are to be treated in the same way.

Cured prints

Fully cured ink is much less problematic than liquid ink. For signs, decorations, phone cases and similar products it is considered uncritical by current knowledge, provided it was cured correctly.

Two caveats:

• Incomplete curing: If the lamp gets weaker or too much ink lies there at once, residues stay uncured. A print that is sticky, smears or smells strongly is not finished. Do not sell it.
• Food contact: Critical. Common inks for desktop UV printers are not intended for direct food contact. Constituents can migrate, that is, pass into food. The European printing ink association EuPIA requires a separate assessment for printing inks on food packaging, with migration testing where needed. A hobby set-up cannot provide that. So: no inside of mugs, no chopping boards, no plates, no drinking straws. The outside of a cup away from the drinking rim is common, but even there you should check your ink manufacturer’s information.

Children and pets

• Store ink, cleaning fluid and waste containers out of reach and closed, ideally in the original container.
• Do not run the printer in a room where children play unsupervised or pets sleep.
• Keep freshly printed parts out of reach until you are sure they are fully cured.
• Do not print UV ink on toys for small children that can be put in the mouth.

For business use

Anyone who employs staff needs a risk assessment and operating instructions for the inks. BG ETEM provides templates for this. For your customers: do not sell printed products for food contact without proof, and include care instructions with everyday items. Keep the safety data sheets to hand in case questions come up.

Continue with: What is UV printing?, Maintaining UV printers and, from the 3D area, Safety in 3D printing.