Finishing Your Prop Kit

Hail, well met, and thank you for purchasing one of our 3D printed prop kits! We’ve collected some tips and common questions we get to help you out on where to go next now that you’ve received your kit! If you have any questions please feel free to contact us and we will be more then happy to help you in any way we can.

Sanding

  • Use a dust mask.
  • We recommend automotive sand paper, it lasts longer! It can also be used wet or dry. Wet sanding (dipping the sand paper in a bucket of water with a bit of dish soap) helps unclog the sand paper and clear dust.
  • Start with 100-150 grit to shear off print lines by sanding ACROSS the print lines or in circular motions.
    • Starting with a finer grit (higher number) or sanding with the grain will take longer.
    • Using sanding blocks or clamps (if possible, some pieces may be too fragile) to hold your piece can make it easier on your hands.
    • Only use plastic grip clamps, metal might dent the print.
  • Sand until you can barely see print lines. Then switch to 220-320 grit. If you’re wet sanding, change the water between sand grits.
  • For finer details on the pieces, fold sandpaper into a sharp crease to get in there.
  • Change your sand paper readily because it wears down quickly and makes it harder for you to use.
  • If you have scratches or places on the print that need filling, we recommend a spot filler! Bondo is the most common, but Apoxie Sculpt and 3M acryl green (unavailable in Canada) works well too. Spread on the filler, it doesn’t have to be smooth cuz you’ll be sanding it when it dries, but avoid creases. Work with the 320 grit to sand away the filler.

What about XTC-3D?

XTC-3D (https://www.smooth-on.com/product-line/xtc-3d/) is a coating that can help smooth and finish plastics, smoothing sanding lines and reducing or eliminating the need for as much sanding, depending on the prop. It is essentially a two part epoxy that you mix together and paint a thin coating over the prop which then hardens over time. Once set, it can be sanded, primed, and painted as easily as any other plastic.

We generally use it on small props like buttons or medallions – pieces that have a lot of intricate curvy details – that would be difficult to hand sand smooth enough.

Assembly and Seam Filling

  • Many of our kits require assembly. We advise doing a ‘dry’ assembly first with no glue/epoxy so that you can see how everything fits together.
  • We generally use a quick-setting 2-part epoxy when we assemble pieces (We get ours at the dollar store and it works quite well) – but others have mentioned good success with super glue, E2000, and others.
    • We’ve found that thicker glues and epoxies work better then thinner/more fluid ones.
  • Use a utility knife to scratch the edges where pieces will join, this gives a rough surface for the glue or epoxy to bite into.
  • Once the glue/epoxy is dried and set, go back down to 150 grit sandpaper to soften the seam and remove excess glue/epoxy.
  • Wipe out or wash excess dust off the piece if needed – sanding dust can obscure places that need filling
  • Apply a seam/spot filler if there are places that look like they need it – and once set sand them down with 320 grit sand paper.
  • If the kit contains screws – you will still want to use epoxy/glue. The combination of the screws and the glue will give it more mechanical strength.

Priming Before Painting

  • Wash and clear out any sanding dust left over before priming.
  • Apply a plastic bonding primer to the piece – we generally use a rattle can/spray can of primer in a neutral color but any plastic bonding primer will work. This first priming will show you any places that still need sanding or filling!
    • Lighter primer colors (grey) are good for light color pieces
    • Darker primer colors (black) are good for pieces that use darker color paints – it can be especially useful for creating shadowed crevices and adding depth to metallic paints.
    • Primer can be beneficial if the prop gets scratched while in use, or for “weathering” where additional layers of paint can be remove to show the ‘base’ material.
    • Always use thin layers of primer.
  • Fill and sand any remaining parts that the primer revealed.
  • Repeat the priming process, if you want. More priming and sanding leads to better results, but even one pass is a lot better then none!
  • Using a finer grit of sand paper (Up to 800 grit wet-sanding) is particularly useful for props that look like metal.
  • Once you’ve got the piece primed and sanded to your desired state – you are ready for painting!

Painting and Sealing

  • We’ve had good luck with a variety of spray paints, acrylic paints, and airbrush/hobby paints. Priming the piece before hand gives you a wide variety of options to choose from! Anything that’s going to bond to the primer will bond to your piece.
  • Standard painters tape is great for masking.
  • Diluted washes of paint and dry brushing are both standard techniques for weathering props. They can give the pieces a lot more depth and make them feel more real. There are tons of videos and tutorials online about weathering props.
  • Once you’ve finished painting your prop – we highly recommend sealing it to protect the all your hard work and increase the durability of the paint.
    • If you haven’t worked with a particular sealant before – we recommend trying it first on another item to make sure it does’t interfere with the paints you’ve used. Some combinations can prevent the paint or sealant from drying properly. It’s not common, but testing it out beforehand can save you a lot of headache.
  • We generally use a matte spray can sealant, but you can use what ever you like.
  • Apply the sealant according to the directions – thin layers work best.

Using Heat to Shape the Prop

You can use heat to make small adjustments to the fit and shape of our props. The plastic we use starts to go soft at about 60C/140F so you don’t need much heat. Heat it lightly, and shape it slowly making small adjustments and reheating as needed. We recommend you do this before painting.

Taking Care of Your Prop

We do our best to make sure our props are durable – and if you’ve followed the directions above for assembly you shouldn’t have very many issues with them. However, they are still plastic and plastic can break if dropped or treated poorly. We don’t recommend children be given free reign with the props – especially if they are longer and thinner as these are more inclined to break when swung or hit against things. If a break does occur – don’t panic! We’ve all been there walking around a convention when a prop decides to disassemble itself!

In the short term (to make it through the rest of the day) you can use a gel super glue to glue the break back together. Hot glue might work in an absolute pinch, but you will need to be careful because the glue is hot enough to soften the plastic. We wouldn’t recommend it for any kind of permanent fix.

In the long term – you can use the same epoxy we recommend above to reattach anything that might have broken. Be generous with the epoxy and it will generally bond harder the the plastic itself so it shouldn’t break again. Just make sure you give it enough time to cure according to the instructions that come with the epoxy!