You’ve recently taken the plunge into 3D printing and would like to know how to go about creating customized paints on your printed parts.
The aim of this article is to give you a basic understanding of painting techniques on 3D prints, both those made with filament printers (FDM) and those made with resin printers (SLA), with the various stages from priming, through airbrushing, to the finishing varnish. What application methods are possible? What are the different types of primers? What type of paint should I choose? What are the different types of varnish?
The aim is to bring to life, by decorating with colors, the figurines, miniatures, COSPLAY prints, but also the various parts and accessories (the list is long) that it’s possible to print with a 3D printer. Whether you’re painting tiny figurines or human-sized parts, you can use the same paints, which are available in a variety of opaque colors, but also in fluorescent, transparent, pearlescent or metallic paint ranges, some of which are even capable of changing color.
In general, the painting technique should follow the same classic stages as for furniture, objects and cars, with the application of primer, paint and, finally, the finishing varnish. The primer’s function is to prepare the surface, clinging to it and leveling it, the paint’s role is to create the color, while the varnish’s role is to create not only protection, but also gloss (or sometimes matte effect).
FDM 3D printers use plastic filament, while resin printers use resin cured by photopolymerization. The result of filament printing is often a tougher, more coarsely finished surface, compared with the extreme precision achievable with SLA printing.
To achieve a beautiful, flawless finish, the substrate must be well prepared, to mask irregularities and small holes, and to eliminate grains and streaks. We therefore recommend careful sanding on medium-sized and large parts. On complicated parts, rinse with water, then dry.
The same paints are used, both water-based airbrush paints and solvent-based paints. In the case of resin printing, 3D printing paint have an excellent ability to bond directly to this material. In the case of plastic printing, it is advisable to take particular care in preparing the substrate and applying an adhesion primer, if you want to guarantee good resistance over time and prevent any risk of delamination (especially when masking or using adhesive stencils).
Preparing the substrate also involves obtaining a surface ready for painting. In the case of FDM plastic pressure, there are often printing streaks, and it’s important to use filler and primer to obtain a perfectly smooth surface. The filler is first used to fill any unevenness in the substrate, and is then sanded with a fairly coarse abrasive paper grit (between 80 and 280). Secondly, solvent-based primer filler is applied with an aerosol or spray gun, to create a thick, self-levelling coat approximately 100 to 150 microns thick. Sanding is then carried out with 320 grit, then 500 grit maximum.
Sanding should be no finer than this, to enable the paint to adhere properly.
In the case of miniature prints, the aim is to preserve all the micro-details of the print. Very fine water-based primers are therefore used, applied with an airbrush.
Finally, the primer also acts as a background color. It provides a homogeneous background, either light or dark, which will accommodate the colors of the figurine or sculpture.
In general, for all bright and clear colors, or even fluorescent colors, a white or light gray primer color is preferred, while dark gray or black colors are preferred for the application of pearlescent or metallic paints.
Whether you’re new to 3D printing, or an experienced specialist, it won’t hurt to read this short paragraph.
Paints are a constantly evolving field: just like other fields and human sciences, innovations improve product qualities, and it’s a good idea to keep abreast of the latest advances or innovations.
Different paint application methods
Applying paint with a fine brush makes it easy to achieve certain lines and small details.
For all other stages, from priming to varnishing, the best method is still spraying. Aerosols can be used if you don’t own an airbrush or spray gun.
However, we strongly recommend investing in a silent mini-compressor and a small airbrush. The painter not only gains in quality of application, precision and possibility, but also quickly saves on the cost of these paints. It’s important to remember that spray cans contain mostly gas and, ultimately, a very small quantity of paint.
If we’re talking about small figurines, then you can use an airbrush with a nozzle between 0.3 mm and 0.5 mm. This extraordinary tool enables you to apply any diluted product and paint, with perfection and speed, objects ranging in size from 1 cm to 25 cm.
Then, if you’re a cosplay enthusiast, you’ll need a slightly larger workshop and a real compressor with a mini spray gun, or even a spray gun with a nozzle between 0.8 mm and 1.5 mm.
Paints for airbrushes
These paints are richly pigmented, yet very fluid. They can be applied with either an airbrush or a spray gun.
Unlike applying color with a brush, you don’t try to cover in one coat with an airbrush. Instead, you apply several thin, light coats, always keeping your airbrush moving from left to right. The great advantage of airbrushing is that only the paint touches the surface, and the tool never touches the surface.
A distinction is made between classic colors, which are opaque or semi-opaque, and special colors.
Special colors are totally transparent colors (called candies), or even pearlescent or metallic pigment-based colors, which are often semi-transparent and require a base color.
There are other colors that can be used in special applications: these are fluorescent paints or chameleon paints, which can change appearance depending on the angle from which they are viewed.
Artistic colors
The artist always works with a plan, a strategy of sorts, to superimpose these different colors and achieve the result he or she is aiming for. Of course, a few tests may be necessary to find the right combination. We always start with the lightest colors, then apply the brighter, darker ones. It is possible to achieve deeper, more real colors, by using transparent colors to modify the background color.
It’s always a good idea to mix and dirty your colors a little with complementary colors. When creating foliage, for example, it’s customary among all great artists to add a hint of red to the green color, to make it look natural.
The details and flashes of light are saved for last.
All colors can be mixed to obtain the desired color. However, we always recommend using primary colors, or pure pigments, for mixing. This gives much better results than mixing colors that have already been mixed, which is notorious for creating dull colors. Pure colors are called “color index” paints.
The difference between water-based and solvent-based paints
Today, the difference in quality between these two major paint families has narrowed considerably. Solvent-based paints are known for their excellent adhesion, rapid drying, fluidity and ease of sanding and working.
Today’s water-based airbrush paints have improved so much in their formulation and chemistry that they have almost nothing to envy the old solvent-based paints. The great disadvantage of solvent-based paints is that they have a very bad odour and are notoriously harmful, making them unsuitable for use in apartments.
With the exception of large-scale projects, such as 1:1 3D prints, we really recommend you opt for the latest generation of acrylic paints for airbrushes, such as Hikari or WPU. These are hybrid formulas between water-soluble acrylics and polyurethanes.
These paints are matte or gloss finishes. This means they are satisfactorily resistant to all types of product, water, detergent and reasonable abrasion or rubbing.
However, we strongly recommend that you always varnish your work. This not only protects the colors with a transparent layer, but also brings out the colors, accentuating the effect of the pearlescent pigments or, on the contrary, giving a natural and homogeneous matte/satin appearance, without spray marks.
There are many brands on the market. Some are well-known but aging brands. Other brands have arrived on the market, notably with French manufacturing, and offer all the properties and advantages of the new, innovative water-based paints, at very affordable prices.
A good acrylic airbrush paint should have the following qualities:
- Ready-to-use: no dilution is necessary, the paint is already diluted and fluid enough to be used with any type of airbrush.
- Solvent-free. The paint is odorless and non-hazardous. It can be used indoors, without the need for a paint mask.
- A quality acrylic must have excellent covering power. This is mainly due to its pigment load. This paint can have excellent covering power without necessarily being thick and viscous.
- A quality paint must cling directly to plastic or resin-type primers, without necessarily having to apply an adhesion primer first.
- Last but not least, the paint must be resistant to sunlight and UVs, without yellowing.
- It must be available in small bottles. This allows the paint to be kept fresh and renewed every year. Some brands offer airbrush paints in 250 ml or 1 l formats, for painting large rooms.
Take a look at this video to see how airbrush paint on a 3D print.