> Hi Phil
> What exactly do you mean by a "planar leveling mark" ?
Here's the 'short form' of the process:
This is exactly what those stray dots suggest on several blocks photographed by Colette Dowell in Campbell's Chamber.Quote
1. You have a block of stone whose specification is that it should be 41" call with a flat planar face on top. First, it is VERY roughly cut to a planar surface to get rid of the bulk of hte excess stone. To do this, you indicate the 41" height by drawing lines around the entire perimeter of the stone to delineate the height of 41". Since the stone is only "rough cut", you might actually have different regions that are exactly 41" high while other, rougher regions are up to 41.5" or 42" high, etc. So you need a way to trim the excess height down to the perimeter marking without huge circular saws and lasers. You need to use a guide that helps you chisel off the excess stone and that lets you know when it's really perfectly flat at nominal height and not hilly or too bumpy, etc.
2. The "guide" that allows you to cut the stone at nominal height and with a flat plane surface is a thick veneer block of stone, wood, or copper that's stiff and flat enough of a plane according to engineering specs; you paint one of the guide's planar faces red and then lay that painted face on top of the rough-cut block of stone. (the veneer must be very rigid and not bend and bow).
3. Then immediately remove the veneer, and you will see paint spots on the highest peaks where the rough cut block touched the veneer. When you see a large concentration of peaks in one area, this means those peaks must be chiseled off in order to slightly lower that part of the block of stone. If the entire veneer is still too high compared to the perimeter spec line, then ALL red dots need to be chiseled off.
4. Repeat #2 and #3 until the plane of the block shows an even distribution of red dots and the veneer is down to the level of the perimeter line that demarcates the nominal height for that block.
How can any of us ever know, when all we can do is think?