Making a bowl from Caithness stone

I have been making a bowl recently and thought I’d show you the different stages in the process. Every stone is different, and my working techniques and choice of blades will vary according to what works best. It’s often a case of just trying things out, and seeing what cuts and abrases best.

Firstly, I selected a sound slab of stone

Disc cutter, with nice new blade, cutting the rough outline.

With this Caithness stone, I initially used a multi purpose 12″ disc cutting blade. I then found a 5″ granite flush cut blade worked much better than the marble/limestone ones. Then a combination of cup wheels, spiracut semi-flexible silicone carbide discs, and velour/velcro sanding discs, then hand sanding with wet and dry paper. A big portion of tenacity, concentration and elbow grease is needed. It’s pretty hard stuff……but lovely, and satisfying.

A cylinder is the first goal. Breaking it down into stages….

I designed the bowl before starting, and made a scale drawing of the section, in order to calculate the largest possible chamfers I could remove to start forming the desired curve for the underside of the bowl. The two lines that describe the chamfer are scribed onto the stone, one on the side and one on the bottom.

Slots cut with a granite blade, then these pieces are tapped off with a hammer. This removes a lot of material quickly.

It’s really important that the first chamfer is very carefully and accurately ground off, and is straight, in section, not curved, as otherwise you’ll never get as much material off as you want, you’ll end up with a chunkier, heavier bowl. You must work to the scribed lines, making a straight cut between them. Eventually the curve is found, once you have taken off a series of incrementally smaller chamfers and roughly rounded everything off.

After removing several chamfers and rounding off

Flipped over and ready to mark out the inside

Compass used to scratch on the inner line

Cut an accurate groove on the line to protect it and to help with visibility later….. it’s a dusty phase coming up and this will help me to get stuck in without taking too much away.

Slots cut with a granite blade, deeper in the middle obvs!

The inside is more tricky as you’re kind of working blind and trying to take enough material away, but without digging in too much. I don’t want this too deep, as it’s a birdbath, and also I’ll be drilling into the bottom for a stainless steel dowel.

Grinding and polishing with the 5″ grinder

Now the stone is brought in for finishing by hand, which is when you can feel it taking shape, and also get rid of all the mini chamfers and kinks in the grinding process. Wet and dry paper is used, from about 60, 80, 120 grit dry, then 120, 240, 320 600 with water.

Here are a few pictures of the finished stone, prior to the final rinse and oiling it. I chose to leave the rough natural top surface as a nice contrast to the smooth underside and interior.