# SLA printers: safety with resin contaminated disposals

I've purchased an Elegoo Mars Pro recently, and I've been watching hundreds of video of all kind of processes, and everyone tells the same: resin is toxic, so you should cure it before throwing it to the trash, otherwise it must be treated as toxic waste.

But I've not been able to find anything with "things that are contaminated with it". For example, if I touch with some paper the resin, I guess that I should let it cure in the sun (like putting it in a plastic box and let it cure, maybe?).

But how about the IPA? How do I treat the rests of IPA contaminated with uncured resin? I don't think leaving something flammable into the sunlight during some hours is the best I can do (maybe I'm wrong and it's totally safe?).

Also, are resins water-washable (like this one from Elegoo) as toxic as the rest? Can I wash them in the faucet, or should I use a plastic recipient with just water and wash them there? What do I do with it once I finish? May I throw it into the bath, or let it cure into the sunlight, or...?

Hope this helps me and some others to treat resin disposals as they should be! Thank you!

• For general handling of a resin printer in your living space, refer to Best way to deal with Resin Printers in your living space – Trish Aug 19 at 22:47
• Partial answer (for pure resin & contaminated material) can be found in Safe way of disposing resin – Trish Aug 19 at 22:49
• Both answers give me more information about the subject and they will be useful for sure (regarding safety, there is never enough information)! Thank you so much! – Unapedra Aug 20 at 6:29

## 1 Answer

The IPA with the resin in it is a chemical waste and toxic to nature. As such, it needs to be given to a chemical waste handler. But those handlers do charge by volume, so you need to find a way to handle volumes reasonably. On the one hand, this means to not use huge volumes for washing the prints but reasonably small batches, and on the other hand to try to saturate them as much as possible before giving them to disposal.

It is not safe to leave the IPA in the sun or close to a source of flame, and it would certainly be not a good idea to try to torch the IPA to try to reduce the volume, but you might manage to try to concentrate the toxic waste if you might have access to a vacuum distillation apparatus - the IPA would be able to be distilled over to be reused while the original material would end concentrated.

At the moment I am waiting for an MSDS of eSun's Water-Washable resin, but the Eleegoo one is available, and it reads that it is classed as "Aquatic Chronic Class 2" - that's better than the Class 4 which IPA-washing resins have, but it is still not Sewer-safe: Do not allow product to reach sewage system or any water source. However, water is much less of a dangerous base for the waste than IPA, making it easier to handle. This mixture too needs to go to a chemical waste handler or be made inert but the waste also can be concentrated with less danger than IPA using a similar apparatus (cold distilling out water) or even a dedicated waste cookpot/evaporation vat that is exposed to heat - though you clearly should do this in a chemical-grade air filtration unit to mitigate the chance of resin fumes escaping into the atmosphere or your work environment if you heat it more than some. The dissolved resin might not be able to cure anymore as the photoinitiator might be used up during it evaporating.

• Even curated resin has to be treated as toxic hazard? I read that curated resin could be thrown away in the trash, and the only problem was uncurated resin. If it's not toxic, then I could maybe leave the contaminated water recipient into the sun (as it's not flammable as IPA) a few hours to ensure the resin leftovers are curated and then treat it as normal trash? – Unapedra Aug 20 at 6:27
• I didn't say that, but only talked about the uncured resin that is in solution in the IPA. I will make that clear in a little. That most certainly a toxic hazard. You can't just "cure it out" in the solution.Leaving the water in the sun will concentrate the solution as water evaporates. – Trish Aug 20 at 8:58
• Now it's crystal clear! So, even if you use water or use IPA to clean your resin printed parts, the rests of the resin and also the fluids used (even water) need to be disposed into a toxic waste facility. The difference between water and IPA is that water is much more easy to work with, has no fumes nor odors, and is easier to treat for the waste disposal facilities (if I understood well). But anyway, both of them are going to cost you a trip to your waste disposal facility. Thank you so much for the response! – Unapedra Aug 20 at 15:07