what is the best technique for polishing parts?
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Sorry to say, your options are limited to sandpaper and more sandpaper.
in fact I thought it would. so I just want to know if it is possible to obtain a completely clear finish.
because I have tried with sandpaper number 1000 and just got duller piece
That’s where option #2 comes in, haha. I keep going to 2500 grit. If 2500 and beyond does not impress you enough either, you can rub it with cooking oil or spray it with acrylic clear coat to get the max clarity out of it.
sounds like a lot of work!
95% of my jobs are cylindrical (plastic bottles). I think I will design a small lathe with a fan motor and hold my pieces with two counterpoints.
are you accomplished polished pieces ?
It is a lot of work. I don’t do it often because it sucks, but yea, I have some that look nice.
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Yeah, with work you can get there. You might want to check out this piece, where @CraigBroady digs into printing and polishing lens. It does take some elbow grease but the results can be fantastic.
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you think it is recommended to use a rotary tool with plush at the tip?
smearing some sand paste
http://www.masherramientas.mx/productos/m/1.1336602880.jpg
@Sam_Jacoby this lense looks great…
I don’t think it would be aggressive enough to get you started, but yes, I think it could work for the next steps. Thermo-platics might smear under heat and pressure, but the Formlabs resin does not melt. The damn stuff is immune to everything but sanding.
You can try an acrylic clear coat spray, which takes less effort than hand polishing (though it never gets as great as hand polishing and patience will get). It will also protect the part from UV and keep it from yellowing over time.
@JoshK “the damn stuff is immune to everything” hahahaha
can you tell me where to buy the spray?
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I have had clear parts polished and after about a minute, they will haze up. Spray with the acrylic clear and they look almost perfect. It is just standard acrylic spray paint clear coat. Most will have UV inhibitors and help to clear up the hazy look of the clear resin with a couple of light coats.
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thank you very much!
will try to get this spray here in mexico.
At least in the US, you can buy these kinds of sprays in hardware and art stores. Anywhere you can buy spraypaint will usually have some kind of clear coat spray. You can get it in satin, semi-gloss, or gloss, but you should choose the high gloss type to make your bottles as transparent as possible (and the most like a PET blowmolded bottle).
maybe in the home-depot 
You could try an air eraser - like an airbrush/miniature sandblaster.
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I have made some clear covers here and we use a series of 500 then 800 grit paper on large flat surfaces and a dremmel for the small curved spaces and then just put a light layer of a clear coat I used a clear rustoleum spray paint to give it the wet look. It is a pain but I am not sure what else you could do to get that absolute clear glass look. I would avoid the sand blaster idea only because the material chips easily after it is cured and you may pit the material to easily.
Straight off the printer
after sanding and dremmel polishing
After clear spray
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