Michelangelo's Pietà, detail of Mary - 3D Printed by richard_swika

I finished the print to make it look like stone by texturing it with sand while the paint was still wet. I surprised myself when it came out so nice, so I made a second one. It came out good, but not as good as the first one. It takes some practice and luck I suppose to do the finishing. Sand very light lightly with 120 to 200 grade sandpaper. If necessary, fill any cracks with sandable caulking (or whatever you have handy, I've used spackling paste in the past with good results. A very good product I use for fixing flaws is Magic Sculpt Epoxy Clay. It is a little expensive, but works very nicely for sculpting on top of 3d prints. Thin it with alcohol to make a paste to fill problem areas. Apply a few very light base coats of: Rust-Oleum Automotive 260510 12-Ounce 2 In 1 Filler and Sandable Primer Spray, Gray. Be sure to sand before and after each coat. After the final coat, burnish with progressively finer grades of steel wool, down to at least 400 to 600. The finish will be super smooth now like glass with few print lines visible. It is ok if you see a few light print lines because they will disappear in the next step. You certainly can stop here, and just a paint it smooth. But I think adding the sand texture enhances the subtle shading of the delicate curved surfaces. You do need a fairly smooth surface for the next step to work. Any flaws will always show through. For the texturing, the easiest way is to use one of the commercial textured spray paints like Rustoleum MultiColor Textured Spray. The finish looks great, but the nozzle tends to clog and can waste an expensive can of paint if you are not careful. So if you like to expirement, you can use sandbox sand, super fine, white. The kind they use in kid's sandboxes. The finer the better. Sift it if you are so inclined or grind it to make it into a dust. You can try buying marble dust or getting it for free from a query. You also need triple thick spray, urethane spray or polyurethane. Something that is super tacky and drys a little bit slowly. The procedure is to get the surface tacky then cover it with sand. Only the layer of sand closest to the surface will stick when it drys. Let it dry a little, then brush off the excess. The timing is critical so it sticks without clumping. You'll be able to even out the surface easily with a brush. Repeat as needed, then spray another coat of of satin over the top to lock in the texture. It takes a little bit of elbow grease, but you can get a very realistic simulated stone surface this way. I've used this same technique with glitter, iron fillings, aluminum dust and marble power with good results.