Before the list of steps you'll have to follow, let's start with a tip: coloring a 3D print is not a time trial. Always start with the best quality you can achieve. If necessary, consider cutting the model into parts. As a filament Marco prefers PLA + to PLA as he finds it more workable when cleaning the print.
You'll find all the products used in this tutorial at the end of the article, these are Marco's tools, some are in picture, some not but everything you'll need is listed!
STEP 1 - Prepare the model
First we go to smooth the model, fix the imperfections and remove any residues of supports. The basic tools: normal and fine glass paper, scalpel, chisel and a nail file.
So let's start cleaning the print, smoothing it, fixing it.
Any problems and cracks (even when multiple printed parts are glued) can be placed with putty plastic. The one in the picture is convenient because it can be used with precision. Then putty, let it dry, remove the excesses with fine paper.
Continue to work and finish the model until you are satisfied.
Tip: it is not easy to see the imperfections in this phase so help yourself with a finger passing it on the model and evaluating with touch.
Finished fixing the model? Well, now a quick wash under water to remove all the dust and dirt. Once it is well dried, we will place the model on a base. This will allow us to work without having to physically touch the model. Personally I use an old piece of wood where I put double-sided tape to which I fix the print. Now we are missing a final step before we start painting.
To make the color hold on plastic we have to prepare it with a primer. There are spray products but in my opinion they are more suitable if you go to paint with an airbrush. For me this in picture is perfect, shake well, leave a few minutes to get rid of the bubbles, take a flat brush, give a first light coat of the product. Let it dry well. Let's give a second light coat, let's dry, third coat of primer to have a compact surface (you shouldn't see the original color of the plastic anymore).
As a primer color, a neutral light gray is better, I use this desert tan because I find it better when I use white and light colors. Now we are ready to have fun with colors !
STEP 2 - Let's paint!
What colors to use? The advice is to use modeling acrylics, there are different brands, all good, and you can also buy boxes of 8 up to 50 colors.
Brushes ? We need some flat-tipped brushes, some medium brushes and fine brushes for details. Also in this case we can buy brush sets with a good cost / quality ratio.
Let's get ready to start, we need the colors we want to use, brushes, water, pallete and something to dry and clean the brushes.
Tip: decide in the beginning the kind of result you want to achieve, which colors to use, what kind of aspect you want to achieve. In this case we want to get a rough look from "old grumbler of the seas" (the print will be a gift for a four-year-old girl, it must be a little scary and a bit funny)
For the body we will use two tones of red and one orange. We begin to give two coats of red as a base.
As a first step we add a dark red, almost black, very diluted. We begin to create shadows and make everything less homogeneous. First light tone, to create the nuances, orange with white given with dry brush and passing quickly on the model.
Tip: better to make light hands, dry, and apply a second coat over the color than using "too much color" at once. Do not pretend to have a compact and covering effect with just one coat of paint.
We repeated the step of giving a touch of color with a dry brush with some red and orange, the effect begins to be pleasant but it is still too little “old scary grumbler”
We need more shadows and shades of color!
Red mixed with little black, always given with a dry brush. Very liquid orange on the underside of the model. Then light touches of lighter and darker color to reach the desired effect. Great, we finished the model body!
Let's start the details, in this case the eyes. Take a fine-tipped brush, spread a few light coats of white until you get a compact effect. We used an ultramarine blue for the pupil, first pure then adding white to give light strokes. Now the black, and we're done.
Tip: make sure you have the right amount of light in the environment where you will color, if you need it, for details, you can use a light with a magnifying glass
STEP 3 - The final touch
We use a clear opaque varnish to protect the coloring. There are specific "top coats" for modeling, generic cans (cheap but could be too aggressive) and products for painters. In this case we use a transparent taken from a painters / artists' store. To make the eyes more expressive we can use a glossy clear enamel.
Tip: the brushes used with acrylic colors can be cleaned under lukewarm water before the color hardens, to clean the brushes used with the enamels used specific solvents