Low Poly Marble Bowl

Stones are beautiful, aren't they? Man continues to be fascinated by diamonds, opals and rubies and the strange, yet appealing, glossiness of metals. We dig deep through rock and dirt to find the best specimens and can only dream about the wonders we will find one day in distant worlds. Stone is also the oldest material used to make something, way before iron or clay was discovered. Even paintings were made on stone walls by the first humans, who felt the need to express their faiths and fears.
Yet, they all look the same when lying on the dirt. To fully discover the true power of a stone, it has to be melt, to extract it's beautiful and useful metals. It has to be lapidated to refract light in the colors of the rainbow. It has to be polished until we can see the world reflected in it. It's not that I don't admire the power that a rough stone can have and the stories it tells. So, for this instructable, I decided to make something shiny from something dull. It's a simple bowl or ashtray made from a marble slab, big enough to draw the design you have in mind. As geometrical designs never go out of style I wanted to go for a low poly game look on the outside and a simple circle on the inside.

• Marble slab
• Small angle grinder
• 4" carbide or diamond disc for stone
• Dremel
• Carbide bit or sandpaper drum for Dremel
• 1 Mallet (I'm using a bell shaped one)
• Point chisel
• Flat chisel
• Wet sandpaper grits 100 to 800 in 100 increments
• Any good quality ceramic floor wax

Safety: Use a respirator even when you work with hand tools. Eye protection is also mandatory. I don't usually put the guard on the grinder so I can go deeper, but that isn't advisable also. Wear some gloves and ear protection.

Gather the manual tools and, with the compass mark two concentric circles on the stone slab. One will be the exterior diameter (roughly) and the other the interior.
Now grab the mallet and the point chisel and start taking some stone out. Try to make a straight line that passes through the center of the circle and start to define the depth and shape of the interior. I made some small perpendicular cuts so I can dig deeper into the groove. Try to start with the point chisel at an angle of 45 degrees and then lower or lift it to take more or less stone. Don't use the chisel perpendicular to the stone in any occasion as you can damage the tool or crack the stone. Also, very important, always work from outside to inside so you don't break the borders of the piece.

Now make another line with the point chisel to form a cross. Try to define shape and depth as you did with the other line. One very useful way to check if the bowl is evenly carved is to make a template in paper or cardboard and insert it in the ridges you made until it fits.
In this step, I usually use the flat chisel to widen the groves and make the bottom plane so the template sits better. Now, with the point chisel, continue to carve the rest of the bowl between the grooves always checking with the template so you dong go too deep. Now move on to the flat chisel and remove the marks left by the point chisel. To even the surface use the angle grinder or the Dremel. Just don't stay too much time in one spot or you'll dig a hole in the stone.

Now turn the slab upside down and draw a circle in there. As the outside is polygonal, this circle is only a marker so I don't take too much of the circular shape.
Still with the slab turned upside down, clamp it to the table and start carving the polygonal sides. Try to keep the cutting wheel always in the same angle so you don't round the facets or create extra ones. With the Dremel try to remove the scratches left by the die grinder. Here I'm using a carbide bit but if you're not very experienced with stone I recommend using a sanding drum. In this step, I decided to make the facets concave to enhance the edges even more, as the stone veins don't help in clearly visualize the shape. I love it when I change my mind in the middle of making something. I think that's what separates us from robots and CNC (which I also admire, of course!).

Now, starting with the coarser sandpaper grit ( usually 80 or 100) Start sanding until you get rid of the scratches left by the Dremel.
Then go over to 200 grit and sand the heavier grit scratches. Always using water, continue to sand the stone in 100 grit increments until 800 grit. When you are happy with the level of glossiness you can stop sanding. Dry the stone with a hairdryer and apply a good quality ceramic floor wax. Read the wax instructions, as some tell you to rub and others to brush. Hope you like the result. Bye!