Porous materials can be submerged in “porosity sealer” and vacuumed. It’s then heated to solidify the polymer. It’s used to plasticize wood, and on automotive parts. A company called Chemsol makes a good one.
You may want to try this kit. It goes from 300-12,000 grit. https://www.pennstateind.com/store/PKFINKIT.html
I appreciate people giving answers, but there's a few bits of incorrect or misleading information posted here. Nylon can be dyed - the dye seeps into the surface of the part and stays there - how does it get there? It's Hyogroscopic, which means it readily absorbs water, and the particles in the water. It will eventually reach maximum saturation for a given humidity (hot hot and humid is your underwear???) That covers the material.... The SLS (selective laser sintering) printing process actually does leave microscopic holes in the layers of the print - with enough layers it's going to be watertight, but the surface will still have some holes to it. I forget the size of them, but it's at the nanometer level IIRC - very tiny, but still there. The MJF (multi-jet-fusion) printing process is much the same, but the reports I have read show that the microscopic holes in that process are much smaller than with SLS. I know the processes are very similar, but are different enough. MJF prints at half the layer height, and they may use a finer grain of powder because the laser is less powerful, which may actually be the source of that benefit. While MJF is only available in grey and black, I actually find the raw prints to be nicer than the color prints and on par or better than the premium finish SLS and it's the same price as natural finish SLS
Have you tested the Smooth Black PA12? It uses a chemical vapor process, which gets the surface pores sealed. I'm very much interested in it, and I'd be quite happy to order a few test prints if you need a guinea pig
I have, and it's the perfect solution (if you like black and don't mind paying for it), however Shapeways will not add it as an option to the Marketplace, even though I've asked nicely... To offer it, I would need to open my own shop on my own platform and program it to order through their API, and I would then be maintaining two shops when I barely have enough time to manage one right now... If it were my full time job, I might consider it, but working 50+ hours at my full time job, plus family, plus that, I just can't do it... Warm Regards, JosieLynn Jewell