Glossary · Material

3D printing

Resin (photopolymer)

The liquid printing material of resin printers: a synthetic resin that hardens under light. It produces very fine parts such as miniatures or jewellery models.

Explained in more detail

Resin is a light-curing synthetic resin, a so-called photopolymer, which on hobby devices cures under light of around 405 nm. It consists largely of acrylates, that is, reactive plastic building blocks. Besides standard resin there are water-washable, tough (ABS-like), flexible, heat-resistant and castable burnout resins. Cold resin becomes viscous, and manufacturers usually recommend at least 20 °C, ideally around 25 to 30 °C. According to safety data sheets, liquid resin irritates the skin, eyes and airways and can trigger an allergy with repeated skin contact.

Where does the term come from?

Resin comes from the Latin resina. Photopolymer is made up of Greek phos, "light", and polymer: a plastic that cross-links under light.

In practice

• Shake the bottle well before printing and stir the resin in the vat, as pigments settle.
• Store resin in the dark, tightly closed and not too warm, Formlabs specifies 10 to 25 °C.
• Wear nitrile gloves and safety glasses when handling liquid resin, even with water-washable resin.
• Wash resin off the skin immediately with soap and water, not with isopropyl alcohol, as Formlabs expressly advises.
• Liquid residues do not belong down the drain: let them cure or take them to hazardous waste collection.

Not to be confused

Printing resin is not the same as casting epoxy resin: casting resin cures by mixing two components, printing resin cures with light. UV ink also cures with light, but it is an ink for the UV printer.

Frequently asked questions

Is water-washable resin harmless?

No. According to the safety data sheet, even water-washable resins irritate skin and eyes, and the data sheet for Anycubic Water-Wash Resin+ even warns of serious eye damage. You need gloves and safety glasses just the same, and the rinse water must not go down the drain uncured.

Does every resin fit every printer?

Most hobby resins cure at 405 nm and run on almost all MSLA printers. Still, check the specifications of the printer and the resin, and take the exposure time from the resin manufacturer's profile as a starting value.