Is UV Resin Toxic? (Cured/Liquid/Vapors)

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Martin has a M.Sc. in physics and has gained many years of experience in industry as a lab manager and quality assurance manager. He has now tested dozens of 3D printers and is happy to share the collected experience with each new article.

UV Resin is Toxic

UV resin is a synthetic resin that is normally in liquid form. The synthetic resin hardens under UV light. The technology of 3D printers that work with resin is based on this.

Liquid resin is toxic and can enter the body through the skin. Resin is bad for your health. And not only your health: the entire printing environment is affected.

What many people do not know: Resin does not yet trigger any severe reactions when it first comes into contact with the skin or mucous membranes. You probably won’t see anything or feel any itching or burning.

However, if you repeatedly expose yourself to the synthetic resin or its vapors, your body will eventually become very sensitive to it. This is similar to a contact allergy, which only builds up over time.

Synthetic resin is widely used in industry and crafts. This is because the material allows many interesting applications, without which the comfort of modern life would be unthinkable. Since contact with the resin is initially unproblematic, occupational safety has long been neglected.

Today we know: The body becomes very sensitive with repeated exposure. After years, the skin reacts very violently to resin. A few vapors in the air are then enough to trigger severe headaches.

This sensitivity is irreversible: once affected, you can never work with the material again without severe pain.

You can avoid such sensitivity by handling the material responsibly and carefully:

avoid contact with the skin
wear personal protective equipment
try to avoid resin fumes outside the printer

Then you can safely work with resin without risking adverse health effects.

So careful and above all reasonable handling of the synthetic resin protects not only you, but also animals and the environment.

Light Hardens Synthetic Resin

UV resin can be extremely harmful. Other technologies of 3D printing are safer. Nevertheless, the resin printer is also suitable for schools, educational institutions and hobbies. To understand the dangers of resin printing, you need to know how exactly the technology works.

The toxicity of the resin is due to the chemical properties of the material. During the printing process, the resin hardens when you direct UV light directly onto the material. Only the hardened, solid resin is no longer toxic.

As long as the resin is liquid or soft, you must not touch it. Because in this state, the special chemical state of the material allows it to penetrate the skin very quickly. This is no longer the case with hardened, solid material.

Cured synthetic resin is even food safe.

3D printing with resin is safe when direct contact with the skin is avoided. This means: Make sure that your skin does not come into contact with the resin!

You use your resin printer not just once in a lifetime, but regularly. Therefore, it makes sense to simply adopt behaviors for greater safety.

Therefore, observe the manufacturer’s safety instructions for each application. Prevention is key!

Too Much UV Light Destroys Resin

UV resin does harden or cures under light and is no longer toxic in this solid state. But too much UV light, too long or too violent exposure, will destroy the material.

So if you expose your object to UV light for too long, for example in the post-processing of your print piece, you risk damage.

As a rule of thumb, you can assume that exposure for about six minutes is quite sufficient to allow even larger resin print pieces to cure completely.

Ignorance

Resin printers are popular in education and training. So the devices are not only in private households. They can also be found in schools, youth centers, fab labs and universities.

Nevertheless, the health consequences of contact with resin are usually not known. Often enough, topics such as personal protective equipment and occupational safety are simply not addressed.

There may be various reasons for this – after all, young people are supposed to learn how to use printers. Those who first have to deal with safety instructions and protective precautions quickly lose interest.

3D printing technologies have developed insanely fast in recent years. The first printers were still very, very expensive from a good ten years ago and only interesting for industrial applications. Companies have paid attention to occupational safety, but this is neglected in the private sector.

While health education in the workplace can be handled well by companies, it’s a different story at home. The manufacturers of 3D printers do provide information that handling resin is not entirely harmless. But nothing more happens.

So you need to do your own research on how to protect yourself when printing with resin. In small offices, schools and private rooms, the health hazards posed by resin must be assessed differently. Most accidents with UV resin happen in the hobby sector because the toxicity of the material is misjudged.

It is an ominous combination: the chemical resin is very dangerous. Initially, contacts with resin show no health consequences. And most people do not know about the fact that the contact poison takes effect only after a certain time. These three parameters come together and pose a serious danger!

UV Resin and Environment

Resin is dangerous not only to humans, but also to other living organisms, including pets and wildlife.

Because home 3D printers are not used in a hermetically sealed environment (kitchen table instead of lab), the material can escape into the printing environment and be carried outside.

The most important point is: how do you dispose of synthetic resin correctly and safely?

Some resin always remains in the bottle. You clean your tools, the tank and other objects. Resin is toxic, so you must not simply throw leftovers and cleaning materials in the trash!

Simply rinsing it off with water is also a bad idea: Resin destroys ecosystems via water. If the resin is disposed of through the sewage system, it kills animals and plants wherever it comes into contact with them. And that’s the entire water cycle system.

As far as that is concerned, the resin is still liquid and not cured. But synthetic resin also decomposes if it comes into contact with UV light for too long. This happens, among other things, when cured resin is exposed to strong sunlight.

For this reason, you should never use models printed from resin outdoors. Direct sunlight contains too high a proportion of UV light. The printed models are therefore a danger to the environment in the garden, in the yard or on the windowsill.

This is because direct sunlight is sufficient to decompose the plastic. In this case, too, particles are released into the environment.

When working with synthetic resin, the following things must be observed:

the danger posed by the liquid resin itself
how to dispose of leftovers and waste safely
how to safely dispose of personal protective equipment
keep resin and printed products of all kinds away from animals

Working Safely with Resin

Now it’s clear how toxic resin is for people and the environment. How can you work safely with such a material? One thing is clear: You have to protect yourself, and you are responsible for protecting your environment.

First, read all the safety instructions that the manufacturer of your 3D printer has put together for you. This may seem tedious. But reading the instructions before each use of the device will have a positive effect: you will remember them and always act responsibly when using the device.

Make sure that you prepare the environment of the printer. You should print in a protected environment. Pets should not be in the room when printing, nor should small children.

Next, prepare yourself and your equipment.

Protective equipment for handling resin:

chemical resistant gloves for hands (better to wear several layers on top of each other)
chemical-resistant safety goggles (laboratory glasses) to protect the eyes
clothing that covers your skin on arms, legs and torso as completely as possible
ideally a disposable overall or a protective gown

It is important that you always wear the heavily covering clothing and personal protective equipment when working with the resin and the 3D printer. This applies not only to the printing itself, but also to the assembly and disassembly of the printer and the post-processing of the printed pieces, as well as during all cleaning work!

Make sure that you work in a well-ventilated room. Under no circumstances should you breathe in the vapors of the synthetic resin! A respirator mask from the hardware store (FFP2 or FFP3) is useful.

Only set up the printer in rooms that you can ventilate well. An air-conditioned room with filtered exhaust air is even better. If you have a workshop with an exhaust system above the work table, this is ideal. Filter systems with activated carbon are often recommended because they can absorb the vapors from the 3D printer well.

Protect the Environment

In any case, you should prevent resin from getting into your surroundings and the environment. Resin is a toxic substance – so treat it as such! In concrete terms, this means keeping your workplace as clean as possible.

Whenever you work with resin, you protect the surfaces and prevent material from dripping, dusting or crumbling. Dispose of all 3D printing waste (liquid, solid, dust) in a safe manner. Observe the regulations for problem waste disposal in your region!

When finishing your printed parts, cover your work surface with a protective film. Always work with a face mask and gloves. Have tissues or toilet paper and a trash bag ready.

After Printing

Once the printing itself is complete, you’re far from done. You’ll need a base for the table or countertop when you’re finishing your printed parts. But before you get to the post-processing, you’ll need to supply your 3D printer.

After printing, there is still excess resin in the tank. Pour it carefully through a sieve back into the bottle, it can be reused. There is also liquid resin on the printing platform and the printing piece itself. Let it drip into the tank.

To do this, you should hang the printing plate diagonally over the tank. As a passionate 3D printing fan, you can find the necessary construction at Thingiverse and produce it yourself. Important: Always work with gloves, goggles and a mouth guard, even when cleaning up!

Once the platform is drained, wipe off the remaining adhesions with paper tissues. Toilet paper will also do. Put the paper in the trash bag immediately so that no liquid resin from the paper gets onto your work surface! Use a spatula or blade to separate your print object and other adhesives from the printing platform.

The printed parts are then placed in a container with isopropanol. Swivel the container until the resin film has dissolved from the surface due to the movement. Alternatively, rinse the printing plate together with the still adhering print object in isopropanol. This also reduces your consumption of paper towels. Keep in mind that you will need a larger cleaning container for this!

For a good print result, it is important that you wash out all excess resin from the corners and crevices. The isopropanol bath is therefore not sufficient. As a rule, you have to help with a soft toothbrush or a brush. This tool must also be cleaned thoroughly afterwards!

Cleaning Fluid

Resin accumulates in the isopropanol when rinsed off. The result is a mixture of resin and alcohol. To ensure that your printing piece is really clean, a second rinse in a fresh isopropanol bath makes sense. Less resin will accumulate here.

If you use a so-called wash-and-cure station (for example from Anycubic), this station must be kept clean. The wash-and-cure station is recommended because it can reduce your consumption of paper towels enormously. Remember: Here, too, you always work with a mouthguard, goggles and gloves! Because there is still liquid resin involved.

You can reuse contaminated isopropanol. To do this, simply leave the container with the washing solution until the resin has settled to the bottom. The isopropanol on top can be used again. Dispose of the residue properly.

Important: Liquid resin is absorbed very, very quickly through the skin and enters the body almost immediately. Therefore, you should avoid contact with the skin at all costs. Resin dissolved in isopropanol is immediately absorbed by the skin! Therefore, please always avoid contact and be especially careful with the isopropanol!

Isopropanol

Isopropanol is an alcohol and therefore highly flammable. You should not inhale the vapors of the cleaning liquid, and you should also protect your hands and eyes when handling it. And you must not simply dispose of isopropanol at the sink or in the toilet.

It is the same with other alcohols such as bioethanol and methylated spirits. These two chemicals also smell extremely unpleasant and are also highly flammable.

Water Washable Resin

Some manufacturers recommend water washable resin*. The advantage of this is that you wash your printing piece and printing plate in a container of water after printing. This is more pleasant and environmentally friendly than working with isopropanol.

But you still must not wash the tools and your printing piece under the tap, because the synthetic resin is still toxic.

This means that you still have to dispose of the water you used for cleaning separately, as well as the isopropanol. In any case, you will need containers in which you can safely store the contaminated liquid.

By the way, you get the resin to flake out of the cleaning fluid via irradiation with UV light.

If you then pour the liquid through a resin filter* into another container, you have a usable cleaning liquid available again. The residue remaining in the filter can be disposed of as problem waste.

Remember, even the filtering is done with a mouth guard, goggles and gloves!

Waste Disposal

It is often advised to cure the leftover resin and then dispose of it in the normal trash. But it is better to dispose of the residue leftover from printing and the resin filtered out of the isopropanol via the recycling center. This varies from country to country!

Therefore, it is worth collecting the residues and waste in tightly sealable containers until it is really worth disposing of them. And this also applies to the isopropanol or other liquids used for post-treatment. Over time, the liquid becomes somewhat gray because resin accumulates in it.

Isopropanol can therefore not be used forever. The grayed liquid eventually leaves gray and white spots on the printing piece. Then it is time to dispose of this liquid as well.

Isopropanol can either evaporate from the opened container (this takes a while and smells very unpleasant), or it is also disposed of via the recycling center.

Together with the remains and used cleaning cloths, also dispose of the used and resin-contaminated disposable gloves and the protective gown or disposable overall.

Do not wear protective clothing that you would wash in the washing machine. Because when you wash it, the synthetic resin gets back into the water cycle – and you want to prevent that at all costs.

Symptoms of Contact with Synthetic Resin

People are different. We don’t know exactly how your skin will react to contact with resin. These are possible symptoms of contact with resin or the fumes it releases:

watery eyes
puffy eyes
eye burning
redness of the skin
allergic contact eczema: pimples, cracks in the skin, wheals, extensive inflammatory reactions
itching or burning sensation on the skin
pain on the skin
burns
respiratory problems: irritated airways, extreme burning of the mucous membranes, shortness of breath, swelling of the airways.

If you experience one (or more) of these symptoms, you should seek medical attention immediately! If you expose yourself to resin fumes, you may also experience headaches, dizziness or nausea. The most common symptoms, however, are eczema, especially on the hands, arms, legs, face and neck.

It is possible that the symptoms will only appear after you have worked with resin several times over a longer period of time. So do not become careless if you have survived the first few prints without damage!

Anyone who works professionally with synthetic resin usually wears several layers of protective clothing and several layers of disposable gloves on top of each other. This is because once a layer is wetted with the synthetic resin, it must be disposed of.

To protect you and those around you from coming into contact with the liquid resin, the stained protective gear actually needs to be disposed of immediately – and in a garbage bag that can be sealed tightly afterwards so that the resin can’t come into contact with anything around the house.

First Aid after Contact with Resin

Should you come into contact with the resin despite all protective measures, quick help is needed:

Remove contaminated clothing immediately.
Wash your skin thoroughly with a mild soap and water.
Ideally, you rinse the affected skin areas with lukewarm water for about 15 minutes.

Important: Never use very warm or hot water. Because this does not help to wash synthetic resin from the skin. On the contrary, the heat causes the pores of the skin to open. This makes it even easier for the synthetic resin to penetrate the body.

Contact with sunlight and UV light should be avoided at all costs. This is because the resin reacts with UV light. It will not harden and easily detach from the skin, but you will completely cauterize your skin.

If the resin sticks, loosen it with a waterless cleaner (do not dispose of it in the sink, but collect it in a bowl). If skin irritation or discomfort occurs, seek medical attention.

In case of eye contact, immediately rinse your eyes with clean water for 20 to 30 minutes. Pull back the eyelids frequently and call an emergency physician. If you receive help, note: First responders should also wear gloves, respiratory protection and protective clothing, as well as goggles, so as not to endanger themselves.

Safe Storage for Resin

To avoid contamination and contact in the home, you should store your resin properly. Temperatures between 15 degrees Celsius and 27 degrees Celsius are ideal. The closed bottles of resin should not be stored next to heat sources or oxidizing agents.

Make sure that the bottles are not exposed to strong light or sunlight. Ideally, you store them in closed containers that are airtight and located in a dark and cool, but well-ventilated room.

Behavior in the Event of Accidental Leakage of Synthetic Resin

If, despite all precautions, synthetic resin gets into the environment or into your home, you must react immediately:

Wear protective clothing, gloves, respirator and goggles.
Extinguish all ignition sources and ventilate the area immediately.
Avoid direct contact with spilled or leaked material.
You can pick up small amounts with paper towels.
Thoroughly clean all contaminated surfaces.
Dispose of protective clothing, cleaning cloths and contaminated items via problem waste disposal.

Are There Any Alternatives to Toxic Resin?

Synthetic resin is basically toxic. Of course, you can only comprehensively avoid the associated risks if you do not work with the material.

But there are a few alternatives: some manufacturers have developed forms of resin that, while not harmless, are at least less damaging to the environment:

Anycubic: plant-based UV resin*
3DResyn suitable for SLA
eSun: a cross between bio-based PLA and SLA resin*

These forms of resin are all toxic as well. You should always wear your protective equipment when working with these materials. This is because contact with the skin can have the same consequences as with conventional resin.

But the fumes released by these supposedly biological alternatives are not quite as dangerous. So it may be enough to set up the 3D printer directly in front of an open window when working. You can do without special ventilation systems at the workplace that include HEPA filters and carbon filters. However, you will still need a respirator.

Resin Prints in Your Home

Since even cured resin decomposes over time under UV light and causes damage to the environment, you should never print the following objects from resin:

Decorations for the garden
Decorations and flower pots for the balcony
Items for your aquarium
Toys for your pets
Children’s toys

Resin is food safe, but ask yourself: Do you want to drink your coffee in the morning sun on the balcony from a resin mug?

The resin will probably not harm the coffee – but daylight will still decompose the resin over time. And then traces of it can get into the coffee. You won’t see that, because the decomposition starts slowly.

Conclusion: Safe handling is possible, but time-consuming

UV resin is a great material and allows you to do amazing things in 3D printing. If you follow the safety precautions, the material is also relatively safe to work with.

Personal protective equipment when working with resin includes safety glasses, respirator, gloves, and some kind of coverall that also covers your arms.

However, make sure that you keep the resin safe at home. Remember that children, guests and pets may be present and could come into contact with the material. You should avoid this at all costs!

Synthetic resin and protective equipment and cleaning cloths contaminated with synthetic resin must not be disposed of with household waste (depending on the regulations of your country or city).

The popular resin printers for hobby use have built-in safety features. These include Auto Stop when the UV shield is not tightly closed.

If you’re working with resin:

Do not wear jewelry such as rings, bracelets or watches.
Wear nitrile gloves (chemical-resistant), safety glasses and a respirator.
Never eat or drink in the work area or even near the resin and printer!
Dispose of contaminated tools and cleaning items at the recycling center.
Never store liquid resin in the refrigerator or in other places where you also store food!
Do not use the printer in bedrooms and lounges, but rather in the garage or a pure workroom.
Protect your fellow residents, especially children and animals, by storing resin safely and using the printer only in a safe place.

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