Coloring is the final stage of work with a 3D-printed model. Despite its apparent simplicity, coloring plastic figures can be difficult. To ensure that the final result does not disappoint, you need to know how to prepare the surface for painting, which materials to choose for each type of plastic.
Painting 3D models
Parts printed on a 3D printer are painted for two purposes:
- to smooth the surface by removing visible boundaries between layers and small irregularities;
- to give the model a finished look.
Depending on the type of material, different methods of treatment and coloring are used.
How to paint PLA, ABS, FLEX and PETG plastic: what dye is the best?
Chemical composition of thermoplastic polymers determines the choice of painting materials (paints):
- PLA is resistant to most solvents, and printed models are characterized by a smooth and hard surface that is difficult to process. Paint adhesion to plastic is poor. The best results are obtained using acrylic pigments and epoxy-based formulations. To increase paint adhesion to the model, PVA glue is added to the paint composition. Cellulose dyes are not bad.
- ABS is a plastic that reacts with acetone and similar solvents. Paint based on them cannot be used for tinting. Epoxy and acrylic dyes hold up well to the surface, effectively hiding cracks and layer boundaries.
- For FLEX products, we recommend elastic coloring compositions: water-dispersion suspension, acrylic copolymer and their mixtures. These paints can mask fine irregularities well and do not crack.
- PETG reacts only with dichloromethane, therefore articles made of this plastic can be coated with any paints, including those based on different solvents. Acrylic is recommended, as nitro enamels and alkyd pigments have a pungent smell that does not evaporate for a long time. Adhesion of acrylic compositions with the surface of the model is worse than that of other dyes. To increase the longevity of the paint it is allowed to spray a layer of varnish on top.
For the work will suit a car aerosol, paint in cans for application with a brush or airbrush. Polyacrylate water-soluble enamel is considered universal, suitable for the treatment of filament of almost any type. The label should indicate “for plastic” or “on plastic”.
Important: Since the surface must be primed before painting, the primer should be chosen in the same way as the paint, so that its base solvents do not spoil the model. Remember that nitro enamels, paints and alkyd-based primer are not suitable for ABS.
How to paint plastic: step by step instructions
The result of the work on painting to a large extent depends on how carefully the surface of the part has been treated. Often the preparatory stage requires more labor and time than the process of painting.
Preparation of plastic before painting
Careful inspection of the model will reveal printing flaws – deep notches and cracks that cannot be removed in the process of sanding and priming. Such defects are corrected with epoxy resin. Small dots and visible boundaries of layers will be hidden by abrasive processing and priming.
Sanding. Performed with sandpaper or abrasive sponge. For roughing take the material with a grain size of P180, finishing performs with sandpaper P400. Use a finer abrasive inexpedient – the glossy surface will not stick to the primer. In the process of sanding small inaccuracies are removed, the surface is matted for better adhesion with paints.
For sanding ABS and PETG it is worth choosing a water-resistant abrasive material and sanding with water. With intensive movements, the surface of the part heats up and the fluidity of the plastic, especially PLA, increases. You need to be patient and work slowly.
Even if the part was treated with solvent, it needs to be sanded to remove the gloss.
Cleaning and degreasing. The model is washed in a soapy solution and dried. Surfactants from soaps work as degreasers. It is recommended to treat it with an antistatic agent additionally, so that the electrified surface will not attract dust.
Primer
Primer is a type of paint that forms a homogeneous surface and increases its adhesion properties. It is available in aerosol cans and brush-type containers.
The primer is applied in two or three layers with mandatory time for the drying of the layers, indicated in the instructions for the composition.
Repeated sanding. Processing of the primed part with an abrasive is necessary to maximize the quality of the surface. For grinding it is recommended to take sandpaper with grit P600 and higher. Since the adhesion of the paint with the primer is high enough, you can not fear that the pigment will not adhere to the glossy surface.
Important: The priming and sanding cycle can be repeated if the result of preparation is not completely satisfactory.
Repeated cleaning. The model is washed with soap and water one more time to remove sanding dust and degrease. The soap solution is best prepared with dishwashing detergent.
Tip. When working with an aerosol, the composition is sprayed in circular motions from a distance of about 20 cm in a thin layer to prevent drips.
What is needed for painting?
Organization of the working space. The place for the application of the primer and paint must be prepared – create an improvised box, which will protect interior objects from flying particles of pigment.
Materials. Paints to choose from: aerosol, in cans. Varnish.
Tools. Brushes – artistic or manicure, airbrush, abrasives for sanding.
Reference. To get a handmade effect, it is necessary to use brushes. Airbrush – the tool of professionals, to work with it is quite difficult.
Painting the plastic
In the process of painting, it is important to observe the main rule – to apply the pigment as thin a layer as possible. It is better to make several translucent layers than one thick one. This will help to avoid stains, which can be difficult to get rid of.
The main tone is formed with spray paint, while details are highlighted with thin brushes. When spraying the can is held at a distance of 10-30 cm distance from the painted surface affects the density of the layer.
Caution: the temperature in the room must be within the limits specified in the recommendations for the use of paintwork materials. During the drying process the product must be protected from dust. The surface must be protected from mechanical influences and high humidity up to the final curing of the paint.
Washing
To emphasize the relief, to highlight the recesses and protrusions, to create shadows, the technique is used – flushing. It is done with the liquid paint: the pigment is diluted 1:1 with the solvent, which is water for acrylic paint. The technique consists in abundant application on the already painted model of a liquid color, the tone of which is much darker than the base.
The paint fills all depressions and remains in them. This visually emphasizes wrinkles, joints between bricks, bolt heads and other small details. The model looks most natural after being washed. For the best flow of paint, the figure is pre-coated with a glossy varnish.
Final processing
Varnishing is the finishing stage of painting. The transparent varnish will give completeness to the appearance, will protect the paint, will increase its durability. To create a transparent layer, different varnishes are available – matte and glossy. Not every model needs a glossy coating. To avoid excessive “playfulness”, it is better to use matte varnish for finishing, for example, the walls of buildings, clothing elements, animal figures.
Synopsis. Lacquer is selected for a composition identical to the paint. For acrylic pigments, water-dispersion acrylic varnish is suitable. It is sold in cans and bottles.
Mistakes of plastic painting and ways to avoid them
Defects arising during coloring are a consequence of trivial miscalculations:
- Stains appear on the model, similar to craters. The reason: traces of grease are left on the surface. Need to carefully degrease the figure before painting.
- Glossy areas are interspersed with matte areas. The primer has not been applied evenly, matte areas appear in places where the primer layer is thinnest and the porous surface absorbs the pigment. The part should be sanded again and the priming process should be repeated.
- Swells or wrinkles appear on the surface. This is the effect of the reaction of incompatible paints. You have to remove all paint, sand the model and repeat the whole process from priming to painting.
Attention! The whole palette of paints and varnishes – from the primer and paints to the finishing varnish – is chosen according to the base solvent.
- Paint leaks on a vertical surface, bubbles and shagging on a horizontal surface. This defect occurs when the pigment layer is applied too thick or when spraying too close to the surface. Painting vertical surfaces requires special attention: the thinner the layer, the lower the risk of dripping paint.
If you follow some simple recommendations, you can avoid mistakes when painting models:
- do not mix different types of paints;
- apply the paint in a thin layer;
- it is necessary to follow the paint manufacturer’s instructions: keep the correct temperature, the drying time of the layers;
The surface must be clean and dry.
3D printer allows you to create a variety of spatial objects. And their further processing turns models into real works of art. Painting three-dimensional figures requires immense patience and adherence to the algorithms of the process, ranging from surface preparation and ending with lacquering. But the final result will be an object of admiration not only by others, but also by the creator of the 3D model.
