3D printing with PLA filament produces amazing models, but the surface often needs smoothing and painting for a professional finish. Applying primer is one of the best ways to prepare PLA for painting. However, choosing the right primer is essential to achieve a smooth, durable, and high-quality finish.
In this guide, we’ll explore the best primers for PLA filament, how to apply them properly, and tips to get the best results.
Why Use Primer on PLA Prints?
Before painting a PLA print, priming offers several benefits:
- Smooths Surface Imperfections: Fills layer lines and minor gaps.
- Improves Paint Adhesion: Prevents paint from peeling or chipping.
- Enhances Durability: Provides a protective base coat.
- Creates a Uniform Base Color: Ensures even paint coverage.
Without primer, the paint may not stick well, and layer lines can still be visible, reducing the overall quality of the finished piece.
Best Types of Primer for PLA Filament
There are different types of primers available for 3D printed PLA models. Let’s explore the best options:
1. Spray Primer (Acrylic-Based)
- Best For: Fast and even application.
- Pros:
- Dries quickly.
- Provides smooth, even coverage.
- Works well with acrylic paints.
- Cons:
- Can be messy.
- Requires a well-ventilated area.
Recommended Brands:
- Rust-Oleum 2X Ultra Cover Primer
- Tamiya Fine Surface Primer
- Krylon ColorMaster Primer
2. Automotive Filler Primer
- Best For: Filling layer lines and small imperfections.
- Pros:
- High-build formula fills gaps and lines.
- Provides a very smooth finish.
- Can be sanded for extra smoothness.
- Cons:
- Requires multiple coats and sanding.
- Strong fumes, so safety precautions are needed.
Recommended Brands:
- Rust-Oleum Automotive Filler Primer
- Dupli-Color Sandable Primer
- Tamiya Grey Filler Primer
3. Brush-On Acrylic Primer
- Best For: Small or detailed prints.
- Pros:
- No spray mess.
- Easy to control on small models.
- Water-based and low odor.
- Cons:
- May require multiple thin coats.
- Can leave brush marks if not applied properly.
Recommended Brands:
- Vallejo Surface Primer
- Army Painter Primer
- Citadel Base Paints (for miniatures)
4. Epoxy Primer
- Best For: Maximum durability and waterproofing.
- Pros:
- Extremely strong adhesion.
- Can smooth layer lines completely.
- Works well for outdoor projects.
- Cons:
- Requires mixing and preparation.
- More expensive than other primers.
Recommended Brands:
- XTC-3D Epoxy Coating
- 3M High-Build Epoxy Primer
5. Gesso (For Artists)
- Best For: Simple priming before painting.
- Pros:
- Easy to apply with a brush.
- Non-toxic and water-based.
- Provides a matte finish.
- Cons:
- Not as smooth as spray primers.
- Requires sanding between layers.
Recommended Brands:
- Liquitex Gesso
- Art Basics Heavy Gesso
- Golden Acrylic Gesso
How to Apply Primer on PLA Prints
To get the best results from your primer, follow these step-by-step instructions:
Step 1: Prepare the 3D Print
- Remove Supports: Carefully remove all supports and excess filament.
- Sand the Surface: Use 220-400 grit sandpaper to smooth out layer lines.
- Clean the Print: Use a damp cloth or isopropyl alcohol to remove dust and grease.
Step 2: Apply the Primer
For Spray Primers:
- Shake the Can: Mix the primer properly for even coverage.
- Spray in Light Coats: Hold the can 6-12 inches away and spray in short bursts.
- Wait Between Coats: Let each coat dry for 15-30 minutes before applying the next.
For Brush-On Primers:
- Use Thin Layers: Apply multiple thin coats instead of one thick coat.
- Let It Dry: Allow each layer to dry before adding more.
- Sand If Needed: Lightly sand between coats for a smoother finish.
Step 3: Sand and Smooth
- Use Fine Grit Sandpaper (600-1000 grit) to remove any rough spots.
- Apply a Second Coat if necessary to fully cover imperfections.
- Final Cleaning: Wipe with a dry cloth before painting.
Tips for the Best Primer Results
- Work in a Ventilated Area: Spray primers release fumes, so use them in an open space.
- Avoid Thick Coats: Too much primer can cause drips and uneven surfaces.
- Choose the Right Color: Use a grey or white primer for most projects. A black primer works well for dark-colored paints.
- Test on a Small Area First: Before applying primer to the entire print, test it on a small section.
- Use a Tack Cloth: To remove fine dust before painting, wipe the print with a tack cloth.
FAQs
1. What is the best primer for PLA miniatures?
For miniatures, Vallejo Surface Primer or Citadel Spray Primer are excellent choices because they provide a fine, smooth finish for detailed models.
2. Can I paint PLA without primer?
Yes, but paint adhesion may be weaker. Using a primer improves the durability and finish of the paint job.
3. Can I use regular household primer on PLA?
Most hardware store primers work, but automotive filler primer is better for 3D prints because it helps fill layer lines.
4. How long should I wait before painting after priming PLA?
It depends on the primer, but generally, you should wait 1-2 hours for spray primer and 6-12 hours for brush-on primer before painting.
5. Is epoxy primer better than spray primer?
Epoxy primer is more durable and completely smooths layer lines, but it is harder to apply. Spray primer is easier to use for most projects.
6. Can I use wood filler instead of primer?
Yes, wood filler can be used to patch gaps in PLA prints before priming, but it is not a replacement for primer itself.
7. Does primer make PLA prints stronger?
Not significantly, but epoxy primers and XTC-3D coatings can add extra strength and durability.
Conclusion
Using the right primer for PLA filament makes a huge difference in the final look of your 3D prints. Spray primers, especially automotive filler primers, work best for smoothing and painting PLA prints. Brush-on primers are great for small models, while epoxy primers provide maximum durability.
By following the correct application techniques and sanding methods, you can achieve a professional-quality finish for your 3D printed projects!