Aardvark: Hmm.... I'm not so sure - have you ever tried using SLS sintered nylon yourself? As far as I can, tell sintered nylon behaves very different from solid/injection moulded nylon in that it appears to "suck up" paint by capillary action.

The 3D printing service I have been using (3DPrintUK in London) seem to ONLY offer an SLS service using white nylon (Nylon PA2200), which runs at 0.1mm layer height. No other materials are on offer.

I must say that so far I am very impressed with both the accuracy of the printouts and the strength of the printed material. e.g. I printed a 7mm piston with a 0.1mm radius gap (i.e. 0.2 mm diam) and after a little light sanding to get rid of surplus dust etc, it seems that was too large a gap so next time I will need to half that gap I think.

What is also quite surprising is that in most instances for some reason, with the naked eye the 0.1mm layers are mostly fairly hard to even see! This feels light years different from the 0.2mm FDM model that I got 3D printed ion ABS whether the layers are pretty in your face.

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Meanwhile I am now experimenting with painting the models with car paint. I must say that I had forgotten just what a messy process spray painting is! For one thing you are not supposed to spray in cold air - tricky in winter, but if you spray indoors it's incredibly messy (!) and even if you spray from a few feet off the ground the paint is still wet when it lands and the paint droplets immediately stick to where they land. Potential nightmare!

Next time I'll try with a paint-brush I think.