Alexei Volkov
Painting 3D prints can be challenging, and there are several factors to consider when choosing the right paint for PLA plastic. PLA, or polylactic acid, is a unique filament material commonly used in 3D printing due to its ease of use. However, its porous surface requires special preparation before painting to ensure a smooth and professional-grade finish. This includes applying a primer, such as a plastic-compatible light or heavy primer, to fill in any imperfections and create a suitable base for the paint to adhere to. Once primed, beginners can use simple acrylic paints, while more advanced techniques include spray paint and airbrushing, which offer a natural and glossy finish.
Characteristics and Values Table for Painting PLA Plastic
| Characteristics | Values |
|---|---|
| Primer | Needed for a suitable surface for paint to stick to and to cover imperfections; light or heavy, sprayed or painted on |
| Paint type | Acrylic-based paints are best; spray paint, brush paint or airbrush paints can be used |
| Paint characteristics | Should not be soluble in water; should be non-toxic |
| Additional steps | Sanding and smoothing out the model before painting; finishing with a clear coat to protect and seal the colours |
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What You'll Learn
Priming PLA plastic
PLA (Polylactic Acid) is one of the most common materials used in 3D printing. It is easy to work with, but some finishing and painting techniques are required to maximise its potential.
Before applying primer to your PLA plastic, it is important to smooth the surface. You can do this by sanding the entire model with 120-grit sandpaper. This will help to remove any small imperfections and create a more even surface for the primer to adhere to. If you want to retain the surface details, you can use a light primer, which will produce a thin coat. However, if you are working with a large PLA print, a heavy primer will be more practical as it will spread thicker and cover any scratches.
Primer is a type of paint that adheres strongly to the plastic and provides a uniform surface for the paint to bond with. It is important to choose a primer that is labelled "plastic-compatible". You can either spray or paint on the primer, depending on your preference and the size of the area you are covering. Spray-on primer is the best way to quickly cover a surface with an even coating. Brush-on primers are available but are more difficult to work with and are better suited for fine touch-ups.
After sanding and applying the initial coat of primer, inspect the surface again for any imperfections. Once you are happy with the surface, apply a final coat of primer. After the manufacturer's specified drying time, the part is ready for painting. You may wish to give it a quick, final polish with a nail buffing stick or polishing paper to ensure the best finish.
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Smoothing PLA plastic
- Chemical Smoothing: This method involves using chemicals like dichloromethane or methylene chloride to dissolve the outer layers of PLA, creating a smooth surface. Dichloromethane is relatively safe if handled carefully due to its sweet smell, which prevents accidental inhalation. However, it is important to take the necessary precautions when working with chemicals. Another chemical option is acetone, which is commonly used for ABS plastics but can also be used on some types of PLA depending on their formulation.
- Heat Gun: Using a heat gun to smooth PLA can be a quick and effective method, but it requires practice to achieve consistent results. Carefully move the heat gun around the print, avoiding staying too long in one area, to evenly heat the PLA until its surface looks wet. Then, turn off the heat gun and let the PLA cool down. This method can give a smooth, shiny finish, but it may not always produce the desired results.
- Liquid Coating or Filler Primer: This method involves using a liquid coating or filler primer, such as XTC-3D or 3D Gloop, to fill in and seal the layers of the PLA print. This creates a smooth surface without the need for sanding.
- Sanding and Polishing: Wet sanding is a chemical-free method that involves using wet sandpaper or submerging the print in water while sanding. It helps prevent the PLA from melting due to friction and reduces the inhalation of dust particles. This technique can be time-consuming but holds paint well and produces a great finish.
- PolySmooth: PolySmooth is a special low-temperature filament similar to PLA that can be smoothed with isopropyl alcohol. You can either spray alcohol onto the finished model or use a PolyMaker Polysher, a machine that evenly coats the prints with vaporized alcohol, resulting in consistent smoothing across multiple prints.
- Primer and Paint: Applying a primer before painting can help smooth out small imperfections in the PLA print. Choose a "plastic-compatible" primer, opting for light primers for small, detailed parts and heavy primers for larger prints to cover scratches and imperfections. You can spray or paint the primer onto the surface, depending on the application.
It is important to note that the chosen method depends on various factors, such as the size of the model, the level of detail, the presence of hard-to-reach areas, and the desired time commitment.
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Painting techniques for PLA plastic
Before painting PLA plastic, it is important to finish and smooth the surface. This can be done by removing any support structures and sanding down any small nubs that are left behind. PLA is unique in that it is not made from petroleum-based compounds, so chemical treatments are not commonly used to smooth the surface. Instead, light sanding or priming can be used to create a smooth base for the paint to adhere to.
Once the PLA plastic has been smoothed, it is time to start treating it with a primer. Primers provide a suitable surface for the paint to stick to and help cover up any small imperfections in the print. When choosing a primer, look for one that is labelled "plastic-compatible". Primers can be light or heavy, with light primers producing a thin coat that is better suited for small and detailed parts, while heavy primers provide thicker coverage that is better for larger prints. Both spray and paint-on primers can be used, and it is recommended to use a combination of both for the best results.
After the primer has dried, you can start painting your PLA plastic. It is important to use a paint that is compatible with plastic and to follow the instructions on the paint container for the best results. You may need multiple coats of paint to achieve the desired coverage and finish.
Finally, once the paint has dried, you may need to apply a clear coat or sealant to protect the paint job and give it a finished look. This can be done with a spray-on or brush-on sealant, depending on the desired finish.
By following these steps and taking the time to finish and smooth the PLA plastic before painting, you can achieve a high-quality, professional-grade finish on your 3D prints.
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Recommended paints for PLA plastic
Painting 3D prints can be challenging, but there are a variety of paints you can use to paint your PLA models. The best paint for PLA is acrylic-based paint, which dries quickly, is easy to clean, and will leave the best overall finish on your 3D print. Beginners often use simple acrylic paints with brushes, as they are easy to control while painting.
Before painting, it is important to finish and smooth your PLA print. The surface of PLA models is porous, so when the first coat of paint is applied, it doesn’t look great. Therefore, to make the surface smooth and to fill the pores, you should always apply a good primer, especially for PLA. Primers provide a suitable surface for the paint to stick to and help cover up small imperfections in the exterior of the print. When choosing a primer, make sure to pick one that is labelled “plastic-compatible”. After 2-3 coats of primer, you can apply multiple coats of paint to get the desired results.
If you are looking for a great quality and beginner-friendly coating for 3D prints, you should check out XTC-3D print coating, which results in a natural and glossy finish. If you are not a beginner, spray paint and airbrush give truly great results. The US Art Supply’s airbrush paint set comes with deep and rich colours that will enhance the beauty of your project. Createx is also known for their high-quality and rich airbrush paints, which are used by a majority of professionals.
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Finishing coats for PLA plastic
PLA (Polylactic Acid) is one of the most common materials used in 3D printing. It is easy to work with, but its potential can be maximized by applying a few finishing and painting techniques.
Before painting a 3D-printed PLA object, it is important to finish and smooth its surface. This can be done by using spot putty, which can be applied with a gloved finger, a small paddle, a plastic scrap, or a popsicle stick. Once the putty has been spread across the surface, it should be left to cure for around 15 minutes. After this, the object can be sanded with 120-grit sandpaper, followed by 220-grit sandpaper. Wet sanding can also be used to achieve a finer finish.
Once the object has been sanded, it is ready for a primer. Primers provide a suitable surface for the paint to stick to and help to cover up small imperfections. When choosing a primer, opt for one that is labeled "plastic-compatible." Light primers produce a thin coat and are suitable for small, detailed parts, while heavy primers are better for larger objects as they spread thicker and cover scratches and other imperfections. Primers can be sprayed or painted on, and it is recommended to use a combination of both.
After the primer has been applied, the object can be painted. Spraying the paint in a back-and-forth motion, overlapping each pass, will help to fill in striations and create a smooth finish. Multiple light coats are better than one heavy coat.
To protect the paint job and add a glossy finish, a clear coat can be applied. This can be done with a clear plastic primer and a UV-resistant clear coat, or with model clear coats like acrylics, enamels, and lacquers. An automotive paint like Dupli-Color Metal Cast Anodized paints can also be used, especially if using flat colors as it has a unique color sheen. Polyurethane, which comes in spray and liquid brush-on forms, can also be used as a protective coating.
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Frequently asked questions
The best paint for PLA plastic is acrylic-based paint. Acrylic paint will leave the best overall finish on your 3D print, requiring only a couple of coats.
The surface of PLA models is porous, so when the first coat of paint is applied, it doesn’t look great. Therefore, to make the surface smooth and to fill in the pores, you should apply a good primer, especially for PLA. You can either spray or paint the primer on the surface.
Spray paint is considered the best alternative to brush painting with acrylics. Spray paints are easy to use, affordable, and can be applied to a large surface area.
XTC-3D print coating is a great option for finishing 3D prints that are already painted. It results in a natural and glossy finish and works for a variety of materials, including PLA.
Beginners can use simple acrylic paints with the help of brushes. These are very simple to use to get proper control while painting. Acrylic paints also dry quickly and are easy to clean.
