The footprints I am copying on the black granite padukas are a great project to explain how the process of sculpting works in general. For a sculptor the process is self-evident, but from the questions I often get, I notice that many people do not know how to get from an idea to a stone statue. Often they think I'll pick up a chisel and hammer and start hammering away. But in this case I want an exact copy of the footprints, and not something carved in freehand. This calls for special measures.
I rarely just start carving. I really only do that if I just want to swing my hammer and have no clear idea. Most often that doesn't work out too well. Usually I start with a small scale model in clay, a clay sketch. If it needs to be a larger sculpture, I will copy the clay sketch to a larger scale. If it needs to be a very precise statue, then the model has to be prepared very precisely as well, because that way there will be much less margin for error. In this case I have the plaster cast with the footprints.
To get from a model to a stone statue I need to transfer a number of measurements. For example, I measure on the model how high up the chin is, how wide is the head is and similar things. The point is just: where do you measure from? You will need to have a fixed point somewhere. But with 1 point your measured distance could end anywhere. With two points you'll limit your possible number of distances to a much smaller area, and only if you measure something from three fixed points, there remains but one solution. For this reason, the technique of the measuring from three fixed points is very old.
This requires you to have three identical fixed points, both on your model and on your block of stone. Any given point that's measured on your model from all three points, can always be found back on the block of stone if you look up those three measurements there. For example 5 cm from point A (to the right), 7 cm from point B (to the left) and 15 cm from point C (to the top). That way you have not only asserted horizontally and vertically, but also the depth.
It's just a hell of a job to measure each point this way. And certainly with a ruler. It means you have to think and remember, and that's how mistakes are made, and you sometimes have to measure hundreds of them. Isn't there another way of doing it? Early on, sculptors learned that it can be done much easier can with calipers and compasses. Other sculptors would use a grid, or a plumb line, but it remained cumbersome.
Until someone came upon the clever idea to hook up a bunch of rods in those three fixed points, and the pointing machine was born. The great thing about this tool is that you can define any point on your model with a needle, you then take up the whole contraption, put it on your stone and voilà, it points exactly where to carve. And better yet, how deep you need to carve. For that needle can slide up to the stop. While carving, you pull it back, you drill or carve a bit, and check the depth with the needle.
At the moment, I'm using such a pointing machine or macchinetta per punta, to very accurately measure the feet and carve them in stone. I've been able to buy an (almost antique) device of brass this week, and the big advantage of this one is that it is very versatile. It usually has a wooden base, the so-called cross. On the cross are steel pins, which are adjusted so that they fit into the fixed points. Those three fixed points are in my case regular Phillips head screws that I screwed into the shelf, but you can also glue nuts onto your statue or something else where the pins fit into. Such a wooden cross is a fixed base and is often annoying when measuring. But my pointing cross base consists of loose brass parts, so I could place it to the side. This way it's not in the way.
On the pointing cross is the actual measuring device. It's a set of brass rods and joints that you can place in any position, with the needle as the main part.
On the plaster feet you can see lots of small crosses. Those are the points I've already measured. Normally, you have to put a dot, but the plaster was too wet, so this time I put a tiny x. I will measure a point, set the needle, and slide it back slightly. The stone is in fact slightly larger than my plaster model, and the needle would move out of position if I didn't pull it back before moving the contraption.
I then pick up the whole thing, the pointing cross with the measuring needle and all, and lift it over to my stone. There, I've also put three Phillips screws in exactly the right place in the wood, and I hook up the device in those. Now the needle points to where I need to drill or carve.
By carefully cutting and regularly checking I can transfer the points in granite to the millimeter. Then it's a matter of connecting the points into surfaces, and only then the artistic process comes in motion: the real shaping.
In all those years as a sculptor I've only had to use the pointing machine a few times. That's because I have another device: a sawing macine that takes a lot of measuring work off my hands. Often enough I will just need another few measurements with a compass and I can carve half the statue in direct carving mode. That will affect the accuracy and depends heavily on the sense of shape of the sculptor, but it is a lot faster, although it leads to slightly more risk of errors. That's something you can never rule out completely, but with a pointing machine that risk would be considerably smaller.
Trying it out for yourself
Want to buy a pointing machine somewhere? Then buy one without a wooden cross. Those things are already quite expensive and without the cross it becomes a lot more affordable. That cross you can just make yourself for each sculpture, with a couple of pieces of wood and a few threaded rods that you grind to sharp ends. That way, you'll always have the pointing cross at the right size. Just be sure the connections are really tight: immovable. The pointing machine itself can be connected to it with a glue clamp.