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I need to smooth some prints with silk PLA filament.

The silk PLA has a nice translucent effect but unfortunately if sanded results in an horrible matte finish regardless the sandpaper grade (I have tried with many grades).

Since I don't have specific solvents or special equipment, and I don't want to paint it as well, I'm wondering if there are alternative ways to smooth the surface.

(Also a my friend speculated about some heat treatment with hair dryer... never heard of something similar and I'm not sure if this could make sense, and in case how should I try).

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  • $\begingroup$ I've had great results with gold silk-like PLA filament, using varying grades down to 12000 micromesh (wet sanding). It's a bit of work, but the stuff shines beautifully. $\endgroup$
    – fred_dot_u
    Feb 17 '20 at 22:42
  • $\begingroup$ some parts can buff up nice in a rock tumbler, if you know how to pick grit... $\endgroup$
    – dandavis
    Feb 18 '20 at 19:15
  • $\begingroup$ tempted to rate "+1 Funny" -- think about it: you want to remove or fill material without removing or filling material! In all seriousness, as fred.u suggests, get a finer mesh polishing paper, or rouge cloth. $\endgroup$
    – Carl Witthoft
    Feb 19 '20 at 15:46
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Unfortunately, there is no way to smooth PLA without sandpaper, solvent or paint - but you can fix the finish after sanding.

If you heat the plastic after sanding to just the point the outer shell starts melting the horrible matte finish goes away and the original color of the plastic returns.

You have to heat the plastic and then remove the heat source just as it's start melting (right before the original color returns, so when you see it working it's too late) because otherwise the object will deform.

I use a heat gun set to 180C and work quickly in short bursts, an hair dryer is probably nowhere as hot, so it will take longer to heat the surface.

You have to do this after sanding, applying enough heat to smooth the layer lines will just cause the object to melt and deform.

Try on a few failed prints first, you will need to get the feel for when to stop heating and you will still probably ruin prints every once in a while.

Another option is to coat the object in an epoxy that will hide the layer lines the best known brand for this is XTC-3D.

If you do decide to paint, you get extra thick primer that's supposed to fill the gaps between the layer lines so you don't need to sand as much (sorry, can't remember the brand name)

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  • $\begingroup$ I don't think most hair dryers can melt PLA. They just take it over glass transition. $\endgroup$
    – R.. GitHub STOP HELPING ICE
    Feb 18 '20 at 4:44
  • $\begingroup$ Use a heat gun instead of a hair dryer, as shown here - same principle, although this is on ABS. $\endgroup$
    – Davo
    Feb 18 '20 at 13:04
  • $\begingroup$ Hair driers aim for about 60 °C $\endgroup$
    – Trish
    Feb 18 '20 at 18:14

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