Complete Guide to IPA for Resin 3D Printing

Resin 3D printing produces stunning detail and smooth surfaces that FDM printers simply cannot match. However, every resin printer operator quickly learns that the printing is only half the battle—the washing and curing process is equally important. At the heart of this post-processing workflow is isopropyl alcohol, the solvent that dissolves and removes uncured resin from your prints. This guide will help you master IPA usage in your resin printing workflow.

Why IPA Is Essential for Resin Printing

When a resin print finishes, it emerges from the vat covered in liquid uncured resin. This sticky, often toxic material must be removed before the print can be safely handled and properly cured. Isopropyl alcohol is the go-to solution because:

• It dissolves most resins effectively: IPA breaks down uncured photopolymer resins without damaging the cured print
• It evaporates cleanly: Unlike water-based cleaners, IPA leaves no residue that could affect surface finish
• It's relatively safe: Compared to other solvents, IPA has a manageable safety profile
• It's affordable and accessible: Readily available from hardware stores and online retailers

Choosing the Right IPA Concentration

For resin printing, concentration matters significantly. The higher the IPA concentration, the more effectively it dissolves uncured resin and the faster it evaporates.

The 1% water content in 99% IPA is low enough that it evaporates quickly with the alcohol, leaving your prints ready for curing. Higher water content can leave prints with a white, hazy appearance and may not fully remove all uncured resin.

Setting Up Your Washing Station

A proper washing setup makes the difference between a frustrating process and an efficient workflow. Here's what you need:

Essential Equipment

• Washing container(s): Use containers with lids to minimise evaporation. Glass or HDPE plastic works well
• Ultrasonic cleaner (optional but recommended): Dramatically improves cleaning efficiency
• Soft brushes: For manual cleaning of detailed areas
• Wash and cure station: Dedicated machines like Anycubic Wash & Cure combine washing and curing
• Nitrile gloves: Essential for handling prints and IPA
• Safety glasses: Protect eyes from splashes

The Two-Container Method

Experienced resin printers often use a two-stage washing process:

1. First wash (dirty IPA): Removes the bulk of uncured resin. This container gets contaminated quickly but handles the heavy lifting
2. Second wash (clean IPA): Final rinse to remove any remaining resin. Keep this container cleaner for finishing touches

This approach extends the usable life of your IPA significantly, as the clean container stays usable longer and the dirty container can be refreshed independently.

The Washing Process

Follow these steps for optimal print cleaning:

Step 1: Initial Drip

After removing the print from the build plate, let excess resin drip back into the vat for 30-60 seconds. This reduces the amount of resin you'll need to wash off and keeps more resin available for future prints.

Step 2: First Wash

Submerge the print in your first (dirty) IPA container. If using an ultrasonic cleaner, run it for 2-3 minutes. For manual washing, agitate the print gently for 3-5 minutes. Use a soft brush to clean detailed areas and supports.

Step 3: Second Wash

Transfer the print to your clean IPA container. Agitate for another 1-2 minutes or run the ultrasonic cleaner briefly. This removes any remaining resin traces.

Step 4: Drying

Remove the print and let it air dry completely. You can use compressed air to speed this process and remove IPA from crevices. Ensure no liquid remains before UV curing.

Maintaining Your IPA

IPA doesn't last forever in a resin printing workflow. It gradually becomes saturated with dissolved resin, reducing its cleaning effectiveness. Here's how to maximize IPA lifespan:

Signs Your IPA Needs Replacement

• Visible cloudiness or discoloration
• Prints emerge still feeling tacky after washing
• Strong resin odour from the IPA
• Visible resin particles or sludge at the bottom

Extending IPA Life

Several techniques can help you get more mileage from your IPA:

• Solar curing: Leave contaminated IPA in a clear container in sunlight. UV light cures the dissolved resin, which settles to the bottom and can be filtered out
• Filtering: Use coffee filters or fine mesh to remove solid particles
• Settling: Let containers sit undisturbed; resin sediment settles and can be decanted
• Use the two-container method: As described above, this keeps your finishing wash cleaner

Cleaning Your Printer with IPA

Beyond washing prints, IPA is essential for printer maintenance:

Build Plate

Clean your build plate with 99% IPA after every print session. Residual resin can cause adhesion problems and contaminate future prints. Wipe thoroughly and ensure no residue remains.

Resin Vat

When changing resins or cleaning after a failed print, carefully wipe the vat with IPA. Be gentle around the FEP film—scratches can ruin print quality. Use a soft, lint-free cloth.

FEP Film

The FEP at the bottom of your vat can be cleaned with IPA, but handle with care. Apply IPA to a soft cloth and wipe gently. Never use abrasive materials or excessive pressure.

LCD Screen (Masked SLA)

If resin spills on the LCD screen, clean it immediately with IPA before it cures. Cured resin on the LCD can permanently damage the screen.

Safety Considerations

Working with IPA and resin requires attention to safety:

Proper Disposal

Contaminated IPA must be disposed of responsibly. It cannot go down the drain or in regular rubbish:

1. Cure the resin: Expose contaminated IPA to UV light (sunlight works) to cure dissolved resin
2. Separate solids: Filter out cured resin particles
3. Evaporate IPA: Allow the liquid to evaporate in a well-ventilated outdoor area
4. Dispose of solids: Cured resin can typically go in regular rubbish
5. Hazardous waste: For large quantities of contaminated IPA, use your local council's hazardous waste disposal service

IPA Alternatives

While IPA is the standard, alternatives exist:

• Water-washable resins: Can be cleaned with water, but results may vary
• Mean Green or Simple Green: Some users report success with these cleaners for certain resins
• Ethanol: Works similarly to IPA but is less common and often more expensive
• Dedicated resin cleaners: Some manufacturers offer proprietary cleaning solutions

However, IPA remains the most reliable and widely recommended option for most resins and applications.

Conclusion

Isopropyl alcohol is the backbone of resin 3D printing post-processing. Understanding how to use it effectively—choosing the right concentration, setting up an efficient washing station, maintaining your IPA supply, and following proper safety practices—will dramatically improve your printing results and experience.

Invest in quality 99% IPA, set up a proper two-stage washing system, and maintain your supplies carefully. Your prints will come out cleaner, your workflow will be more efficient, and you'll save money in the long run. Happy printing!