How to Wash and Cure Resin Prints: Solvents and Timing

A part fresh off the build plate is not finished. It is a green-state polymer with a film of liquid resin on every surface and half-reacted chains underneath. Knowing how to wash and cure resin prints is what turns that sticky, slightly soft object into a rigid, handleable part, and both steps have a wrong direction. Wash too long and the solvent attacks the surface. Cure a wet part and it can crack. Skip the cure and it stays tacky and weak. The numbers below come from vendor documentation, so you can set a timer instead of guessing.

Why the print is not done when it leaves the vat

An MSLA printer exposes each layer at 405 nm for a few seconds, enough to gel the layer and bond it to the one below, not enough to finish the reaction. Formlabs describes post-curing as light-initiated cross-linking that raises strength, stiffness, surface hardness, toughness and temperature resistance over the green part. The wash comes first because any liquid resin left on the surface cures into a glossy, dimension-shifting skin the moment the part sees UV.

The order is fixed: wash, rinse, dry, cure.

Step 1: wash in the right solvent for the right time

Solvent. Isopropyl alcohol (IPA) is the default. Siraya Tech’s cleaning guide calls for 95% or higher IPA, and Formlabs requires 99% or higher for its biocompatible resins. Pharmacy 70% rubbing alcohol is 30% water and leaves a cloudy film. Formlabs also lists tripropylene glycol monomethyl ether (TPM) as a compatible alternative, with the note to use longer wash times if needed.

Two baths. Use a dirty first bath that takes the bulk of the resin and a clean second bath for the final rinse. Siraya Tech is explicit that dirty alcohol produces cloudy surfaces, so the second bath sets the finish. When the first bath turns opaque, retire it and promote the second.

Time. This is where hobbyists overdo it. The Prusa CW1 defaults to a 3 minute wash, and the same page says not to wash in IPA for more than 10 minutes because of surface cracks. Siraya Tech’s window is 2 to 5 minutes. Formlabs’ per-resin figures for its automated Form Wash show how much the ceiling depends on chemistry: 5 minutes for its V5 general-purpose resins, 20 minutes for Durable, and a hard limit of 6 minutes total for High Temp Resin because “excessive solvent exposure affects the quality of the final part.”

Agitation beats soaking. A rotating basket or an ultrasonic cleaner reaches hollows and support forests that a still bath never does; by hand, swirl and brush the support side in the second bath. Hollowed parts need their drain holes flushed with a squeeze bottle of IPA; trapped resin inside a hollow is the classic cause of a part that cracks weeks later.

Step 2: rinse and dry, completely

Prusa’s sequence is to wash in IPA, then rinse under running water and dry with paper towel before the machine’s own 3 minute warm-air drying cycle. The dry matters more than most guides admit: Siraya Tech’s water-washable guide states that failure to dry before curing may lead to cracks. Compressed air or a cool hair dryer speeds this up. A part that still smells strongly of IPA is not dry.

Step 3: cure under 405 nm, with heat if you can get it

Wavelength. Consumer resins are formulated for 405 nm. Anycubic’s Wash and Cure 3 Plus runs ten 405 nm LEDs at 36 W with a 1 to 30 minute timer. Siraya Tech specifies 395 to 405 nm. Sunlight works; expect tens of minutes, and rotate the part.

Time. Siraya Tech’s general range is 2 to 10 minutes under a lamp, 1 to 2 minutes for its Simple resin. Anycubic’s Water-Wash Resin 2.0 datasheet specifies 3 minutes at 405 nm at 25,000 to 30,000 µW/cm². The Prusa CW1 defaults to 3 minutes and its documentation says to re-run the cycle if the part is still sticky. Flip the part halfway; the face on the turntable gets no direct light.

Heat. Warmth accelerates the reaction, which is why the Form Cure heats to 60 °C and runs 14.5 mW/cm² at 405 nm. A study in Polymers on a 405 nm SLA dental resin post-cured at 40, 60 and 80 °C for 15 to 120 minutes found higher temperature improved flexural strength and Vickers hardness at every duration, reaching 147.48 ± 5.82 MPa at 80 °C for 120 minutes, with hardness of 19.4 to 25.7 at 80 °C against 14.89 to 17.51 at 40 °C. A budget station has no heater; a warm room helps, a kitchen oven is never acceptable.

Over-curing. Parts that go chalky or snap where they used to flex have been left too long. Cure in short cycles and stop when the surface passes the checks below.

Settings for one common setup

Standard grey 405 nm resin on a Mars, Saturn or Photon class printer, washed in a Mercury or Wash and Cure class station with 95% or higher IPA:

Step	Setting	Source
First wash (dirty bath)	2 min, agitated	Siraya Tech 2 to 5 min window
Second wash (clean bath)	1 to 2 min, brush supports	Siraya Tech two-container method
Total solvent time	never above 10 min	Prusa CW1 washing guidance
Rinse	running water, then blot	Prusa CW1 drying and curing
Dry	until no IPA smell; 3 min warm air if available	Prusa CW1 default
Cure	3 min at 405 nm, flip, 3 min more	Prusa default, Anycubic datasheet

For water-washable resin, swap IPA for water and wash at least 5 minutes per Anycubic’s datasheet. If you use Siraya Tech Simple, keep alcohol exposure under 30 seconds. Water-washable formulations absorb water, so the dry step is not optional.

How to verify the result

• Tack test. A gloved fingertip on a flat face should leave no print and feel dry, not waxy. Sticky means under-washed or under-cured; if a second cure cycle does not fix it, the wash was the problem.
• Surface. Uniform matte with crisp support nubs. Cloudy white haze points to a dirty second bath or water in the IPA. Cracks during or just after curing point to a wet part or solvent trapped in a hollow.
• Fit. Print a piece with a 5 mm peg and hole and check it after curing, not before. See how to calibrate resin exposure time and the resin calibrator.

Safety and disposal, briefly

Formlabs specifies nitrile or neoprene gloves, not latex, warns that skin contact may cause an allergic reaction, and says to wash skin with soap and water rather than alcohol, which drives resin deeper.

IPA is the bigger fire risk in the room. A 99% IPA safety data sheet lists a flash point of 12 °C, classifies it as a highly flammable liquid and vapour (H225), and notes that the vapour is heavier than air, spreads along the ground, and can ignite at a distance. Prusa gives a fill level of 2 to 3 cm below the tank edge. Keep the bath lidded between uses and away from the printer’s power supply, and never cure with the wash bucket still inside the station.

Used IPA and used wash water are handled the same way: let the solids settle, leave the container open in sunlight until the dissolved resin cures, then dispose of it as solid plastic waste. Anycubic is blunt about the alternative: do not drain it into the sewer. If the same room holds an FDM machine, the ventilation guidance on FDM Desk applies too, and the wash station belongs as far from the hot end as the room allows.

See also

• How to calibrate resin exposure time on an MSLA printer
• Resin print not sticking to the build plate
• Resin 3D printing starter kit: what you actually need
• Resin exposure and cure calibrator
• Desktop FDM printing guides
• Slicer profiles and tuning

Related across the network

• Resin Types Compared: Which Anycubic Resin to Print With — anycubicguide.com
• Anycubic Bed Leveling: The Paper Method and Z Offset — anycubicguide.com
• Photon File Validator: Check Files Before You Print — anycubicguide.com
• Resin MSLA or High Speed FDM: Which Process to Choose — anycubicguide.com
• Best Filament for Beginners: What to Buy First — 3dfilamentguide.com

Related on this site

• How to Dispose of 3D Printer Resin Safely: Cure It Solid First, Then Sort It by Waste Stream