Painting 3D printed models

Author: Martin REK

E-mail: seznam.cz

Painting tanks and other vehicles from a 3D printer is one of the most important steps to achieve a more or less realistic look, so that the model looks like a smaller version of the original and the photo looks like a real machine.

In this document, I will try to give everyone an idea of how I go about the painting process. I always try to keep the cost down as much as possible while still getting the best results. Not everyone may agree with me and I admit that my work is very far from professional procedures. However, I still try to stick to the idea that an RC model should mainly ride and then look. That's why I don't overdo it with details and workmanship, simply because I would be sorry to spend half a year painting and patinating and then crash the model into a wall and destroy the whole part. It's still "just" an RC model.

I've been "refining" the methods I used for several years to achieve the optimal ratio of price, labor and final effect. It simply cannot be cheaper or easier to achieve good results, so I ask that no procedure be omitted. In particular, the application of primer and final clear coat, even though they may seem unnecessary and not have such a major effect on the appearance, then they have a great influence on the other work procedures applied and, for example, the mutual compatibility of colours could cause difficulties.

1. Print material colour

I always try to print all parts of the model from the same colour as the material the part is actually made from. All parts that are actually metal I print from metal colored filament, such as the hull, turret, frame, fenders, etc. Parts that are rubber/rubber, such as the running wheel hoops, I print from black colored filament.

The reason is simple, if I scuff the paint somewhere, it doesn't bother me because the scuff will look real and I won't get banana yellow or blood red coming out from under the paint. So I don't have to worry about repainting the damaged area, and even sometimes I'll do some scuffs on purpose to make the model look good.

2. Gluing parts of the same color

Before I start painting the model, I always need to glue together the parts that will form one structural unit, while leaving all the parts that will move or be hard to access for later painting separately, i.e. I glue the whole hull including all its parts together so I can paint it as a whole. Conversely, I will not glue and fit wheels, shovel and pick to the fender and hatch, which I want to be able to open later without the paint sticking. So, for example, I will paint the wheels separately and put them on later, because by the time they are on I wouldn't be able to paint them. This is also true of belts etc.

3. Sanding and sealing

When I'm joining two parts together, you may see a transition that shouldn't be there. So I have to take sandpaper and sand off the excess glue and the edge that has formed. I also often run the sandpaper over the entire model to smooth out unwanted surface texture and print marks.

The picture shows the SdKfz 222 hull where I sanded the edges after gluing and also the flat areas where the print layers were very visible:

Sometimes it is possible that the gluing point cannot be sanded or smoothed well. That's where a fine sandable body sealant comes in. It's relatively cheap and one can lasts for twenty models. It's available at any paint store. All you have to do is say "fine sandable body putty" to the salesman and he'll know what to reach for. I recommend fiberglass-free. After mixing it, according to the instructions, I just apply it and after it cures, I sand the spot like in the pictures:

4. Base colour

The next very important step is to apply the base colour. I use the base paint to unify the entire surface and prepare it for the application of other paints. It is important not to skip this step. I use a "Spray Filler" for this. It's a car body primer that is specially designed for good adhesion, good hiding power and even fills in surface pores and fine irregularities. If I skip this step, the topcoat may not adhere well to an unprepared substrate, the surface will have an uneven texture, and each part may have a different shade under the topcoat. The use of a filler, in short, is essential.

Pictured here is the filler sprayed turret and running gear of an LT-38 tank:

5. Top colour

I always use spray paint for the top coat. The brush is not suitable for large areas because it leaves stroke marks and it would take a very long time to paint. Spray paint can be purchased at any hobby market or paint store. I almost exclusively use acrylic paints similar to those used by graffiti spray painters. I don't use model paints for this step because I would use a lot of them due to the size of the models, and model paints are simply too expensive. Now I just need to pick the right shade.

If I want a solid color camouflage on the model, the choice of shade is obvious. However, if I want a multi-colour camouflage I always choose a colour that could be considered a base colour and the various spots and lines are painted on top of it. If all the camouflage colors on a vehicle are roughly equal, I always spray the model with the lightest shade found in the camouflage scheme, because it is easier to cover a light color with a dark spot than a dark color with a light spot.

If I want to make a camouflage scheme like the one shown in the bottom left, I spray the model with sand paint and then apply stripes of green and brown.

If I want to do a camouflage scheme like the picture on the bottom right, I choose yellow as a base, which has the same proportion as the other colours, but is the lightest and can be covered well with darker shades.

Models sprayed with first top colour. Sand yellow on SdKfz 222 and basic yellow on LT-38.

6. Camouflage

In case of only one-colour camouflage, when the whole vehicle will be green or e.g. grey, this step ends the basic painting. If I am doing a multi-colour camouflage, I will now start applying the other colours. I have found tamiya model acrylic paints to be the most useful in creating a camouflage pattern.

These paints can be applied by brush or spray. They are available in any model shop or on the internet. First, I choose which method I will use to apply the paint. If the camouflage paint in question has fine gradients and I have an airbrush spray gun then the choice is clear and I will proceed as in the picture. First one shade, then the other shade.

Most modelers don't have airbrush available and most camouflage patterns don't have subtle transitions but sharp edges between shades of colors. Thus I use a brush for painting. Similar to spraying, I first apply the camouflage spots of one shade and then the other.

7. Inscriptions, decals and stickers

At this point it is possible to put various inscriptions, symbols, logos, signs, decals and stickers on the model. I personally paint everything with a brush. If you have some stickers and decals you can apply them as well.

8. Colourless varnish

The last very important step is to fix the whole model with a colourless varnish.

The clear coat will again unify the whole surface. Each layer of paint and each spot on the camouflage could have been applied with a different color, a different process and the resulting surface may not be uniform and may look bad.

After applying the clear coat, the surface of the entire model will be the same, with the same shine and the transitions between colors will not be noticeable. Also, the clearcoat will protect the colors from rubbing off and fix them for future procedures. It will also fix lettering, decals and stickers on the surface.

Paintless varnish is a step that is very important not to skip.

I exclusively use matte acrylic clear spray varnishes. They are not expensive and one spray can goes out for approximately one model. They are available again at any hobby shop or paint store.

The shop staff can certainly help with the selection. Just stress that it must be an acrylic varnish.

That's the basic part over. The model has been painted and it certainly turned out great.

To make the model not look like it has just rolled off the production line, but like it has already put a few miles on it, or fought a few battles, we can move on to the next step, but it is not necessary.

Patinating the model

Patination is the process by which a model in particular is given a soul and ceases to be a toy, but a true miniature of the real machine. If our model starts to get a little rusty, dirty and scuffed, it will look like it has been through several Soviet offensives, and not like a museum piece or a toy in a child's room.

Patination is a science in itself and there are dozens of publications and entire books on how patination should be done. Masters of patination spend months on a model. I certainly don't count myself among the masters, and I don't plan to. For an RC model, I personally am happy with a few simple procedures that I perform.

1. Chipping

The first step is drawing scratches and scuffs.

The easiest option, if you have printed the parts from materials of the right color, is to rub it off normally. If the fender, which is actually sheet metal, is printed from metallic colored filament I can lightly sandpaper or knife it in a few places. I don't have to scrape all the way down to the plastic, fine scratches will just lighten the paint slightly, medium will go to the base color and deep to the "metal". To get a good effect you need to combine them so they are not all on metal, but varied, like a real vehicle.

I always do the other scuffs with paint. I use the dark metallic shades of tamiya acrylic paints I mentioned before for this. I take a torn off piece of dish sponge, dip it into the paint, squeeze it against a piece of paper to squeeze out the excess paint, and then gently press/press it onto the model to make irregular dots of scuffs.

But beware!!!! Less is more! It is necessary not to overdo it and to make only a few abrasions. I recommend to see photos of combat vehicles actually damaged and worn in combat beforehand. It's also a good idea to think about where I'm going to do the scuffs. There will definitely be a lot more scuffs on the steps or fenders than on the top of the hull, gun, etc.

I can also do chipping with a fine brush etc. After doing this method, the whole model needs to be fixed with clear acrylic varnish.

2. Wash/shadowing

To shade the model, it is necessary to fix the whole model with a well-dried acrylic colourless varnish, as described above.

The whole process consists of gradually coating parts of the model with diluted paint, which I then wipe off with a cloth while still wet, leaving the paint in the joints, edges and other places. It also adds an aging effect to the paint.

Umton oil paints have worked best for me for this process. Black with a little brown, lightly diluted with turpentine or regular alcohol. All can be bought at an art supply or stationery store. Try both, alcohol or turpentine and see which suits you better.

Oil paint on the left and turpentine oil on the right:

I stir a small amount in a glass, or better in a "shot" and paint with a hard brush on the model.

I do this in batches so I can wipe off the mixture before it dries. Once I've painted a section, I use a cloth stretched over my finger to carefully wipe off the large and protruding areas so that the mixture stays in the joints, crevices, corners and folds.

Again, I repeat that the model must first be sprayed with a clear acrylic varnish that has been thoroughly dry for at least a day. If the varnish is missing, not dry, then I will wipe off the paint with a cloth or the turpentine will disturb it. If the varnish is not acrylic, then turpentine may dissolve it.

A couple of photos of the application of the mixture:

Once I have the whole piece finished, I need to let it dry for at least two days because turpentine oil doesn't dry as quickly as acrylic or synthetic paints.

When it's done, and the model has dried for at least two days, I spray the whole thing with a clear acrylic matte varnish. The final effect looks very good:

3. Chipping again

I always shade some of the scratches and scuffs so that they are not very visible or disappear completely. Since shading simulates the aging of the model, if I do the chipping again, I will make the scratches in the model look newer than the previous ones. I recommend doing the chipping again in some places. Again, you need to not overdo it.

4. Dry-brush

With the dry-brush method, I can lighten the edges of some parts. Especially metal surfaces that are not painted with paint or are supposed to have a purely metallic feel.

First I paint the whole part with black paint and let it dry properly. Then I dip a soft brush only to the tips in silverware and lightly brush it into the paper. Immediately afterwards, I lightly run this brush over the entire model as if I were applying powder. The result will be that the silverware will only catch on the edges of the part.

Metallic touch up using dry-brush on the tank jack:

5. Details

Only your imagination can help with the other details. For example, the smoked exhaust tip is coated with real soot from the fireplace and then sprayed with a colourless varnish that fixes the soot and makes sure it doesn't smell. A little brown paint or brown oil paint will take care of the rust spots. Dusty spots are clogged with real dust and fixed with clearcoat. Mud is simply a mixture of fine, oversaturated clay from the garden mixed with wood glue. All it takes is a little imagination and the many details bring the whole model to life beautifully.

6. Painting of the tracks

Painting the tracks is the easiest part of the whole construction. I always print tracks of steel grey or silver coloured filament. This is more important with tracks than anywhere else. This is because the tracks are the most subject to wear and tear, and the most likely to wear out when running. And it is preferable that a metallic grey should come out from under the scuffed paint than, for example, blue, etc. After printing, I simply assemble and join the articles and lightly spray them all over with dark brown paint, ideally matt, or subsequently repaint them with matt varnish. The dark brown shade looks like corrosion and dirt together. Then just take a couple of runs outside on the dirt and the edges of the tracks get sanded off and the real dirt does the rest. If in the course of operation a link cracks and needs to be replaced, there is no harm at all and repaint with a different shade of brown. The belt will then not be uniform and it will look like it was repaired in combat conditions.

Example of painting French "Turtle" camouflage on Renault FT-17 tank

1. Printing from filament that has a metallic color and gluing and assembling parts that will have the same color and will be easy to color together.

2. Spraying the primer with a filler

3. Spraying with a base shade of topcoat - running gear and wheel tensioners are sprayed separately. If I mounted it, it wouldn't be possible to paint it afterwards.