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In these steps we will assume at this point you have attached any pieces you need to, and used spot glaze putty where needed for any nooks and crannies, seams, etc.
Step 1: Sanding
There are many types of “sandpaper” you can use. Common ones are flat sandpaper, sanding bricks, emery boards, palm mouse sanders, and orbital sanders. While that is not all of them, those are the main ones you will probably use while working on your kit.
Sandpaper comes in “grits” this number tells you how fine the sand is; think of it like thread count on sheets. The lower the number, the rougher the sandpaper is.
For working on props, armor, helmets, etc. you will start with a rougher grit, usually about a 150 grit, and work your way to a finer grit. We’d suggest starting with 150, then going to 220, and finishing with 320. You *can* also go to a 400 or 600 for very fine precision work, but for most items that is not necessary. This is so your prop gets smoother as you go along, so your items are smooth and even. Paint adheres more evenly to a smooth surface, so you want to avoid painting directly onto a rough surface, but instead do lots of surface prep before painting.
With sand paper and sanding bricks, you can either use them dry or with water to do “wet sanding”. Wet sanding typically cuts down on dust and you don’t get as much scratching so it will get things very smooth.
Always remember to wipe off/dust off before painting after sanding!
Step 2- Cleaning
Cleaning is an important step before painting because a lot of printing and casting processes can leave behind residues of release agents, uncured resin, or other types of chemicals, as well as any natural oils from your hands. If any of these are left before you paint you can have issues with paint adhesion or curing.
#1- SAND!!! Get those props, helmets, and armor smooth. No 3D print lines, no bumps, ridges, etc.
#2 – Give it a good clean. If it’s dusty brush off/blow off/vacuum off any of that.
#3- Give it a “wet clean”. This can range from simply rinsing it off with water, to using dish soap, de-greasing cleaners, or solvents (such as denatured alcohol, rubbing alcohol, or even in some cases a harsher solvent like acetone.)
It’s best practice to use the least harsh cleaning agent possible.
Denatured alcohol and rubbing alcohol will be the most gentle of the solvent options.
Acetone you might not want to use on all surfaces as it is a bit harsher. If you want to use acetone, it’s best to have a towel or rag very lightly wet with it and use that to apply it, as if you put a large amount on it, acetone can “melt” or break down some materials.
Using just water, or just water and soap is useful to wash the worst of the dust and whatnot off. You do not need chemicals. For a final clean after it dries, a cloth damp with alcohol for a final wipe down is a great idea.
#4- Dry it 😀 Be sure to keep it dry and dust free after cleaning before you move on to priming and painting.
#5- Prime it! It’s a good idea to prime your item before painting- we will go into that in depth in next week’s post!
Step 3: Priming
After you sand and clean your props, but before you paint them, you should prime your props/armor/helmet.
If you are working on a 3D printed item and still have print lines/ridges to fill, you should consider a buildable, sandable primer. A decent and readily available one you can get is the Rustoleum Filler Primer, which you can get at a hardware store or Walmart, in either the automotive section or the spray paint aisle, depending on the store. The spray paint version is our favorite. With this you can spray on a thin layer at a time, and sand it after it dries quite easily. It will fill lines, gaps, holes, etc.
For metal, resin, Sintra, etc., you can use any spray paint as a base layer, you don’t *have* to use a true primer as many spray paints are formulated to have better adhesion directly to surfaces as to not need a primer specific layer. That being said, a primer is a good idea to give you a clean bonding surface for your paint.
If you needed to use a filler primer, once your surface is fully smooth, it’s best to then hit it with one last coat of a regular primer before moving to paint.
Primers come in several colors so it is recommended to use one that is close to your base layer of paint. One of our favorite brands is Rustoleum (for both primer and paint), which is easy to get and available in a wide variety of colors at hardware stores, craft stores, Target, Walmart, etc.
If you’re painting aluminum specifically, you may need to use a “self etching primer”. Self etching primers have an added acid that help it to bond better to the metal directly.
You may need more than one coat of primer, be sure that your surfaces after priming are smooth and even. It is best to do one final sanding pass on top of each layer of primer for best adhesion and keeping the surfaces smooth. Use at least a 220 grit sandpaper for this, and be sure to wipe or blow of any dust. We also recommend using the same brand of paint across primer and paint for best chemical interactions. Though paints are similar, different brands may have a different chemical balance, and changing brands can sometimes create issues.
After you have primed your props, you’re ready for paint!
(Ty Callisto and Lonewolf for letting us use their content here.)
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