Petrie's Infamous Core #7 with a lot of pictures of it.
Chris Dunn visited the Petrie museum in London, and concluded that the thin grooves on the outside of the famous granite core nr 7 were spirals
instead of horizontal rings.
That undermines my proposed acidic theory. Which will leave behind only horizontal rings.
However, there are some remarks from Chris Dunn on that page 6, which strongly indicate the use of an etching agent, like an acid :
The crystalline structure of the core under microscope was beyond my ability to evaluate. I could not determine as surely as Petrie did that the
groove ran deeper through the quartz than the felspar. I did notice that there were some regions, very few, where the biotite (black mica)
appeared to be ripped from the felspar in a way that is similar to other artifacts found in Egypt. However, the groove passed through other areas
quite cleanly without any such ripping effect. Though again, I support Brownlee's assertions that a cutting force against the material could rip
the crystals from the felspar substrate.
-snip-
The depths of the grooves were .002 and .005 inch. (Actually, because there were clearly discontinuities in the groove at some locations around
the core, the actual measurement would be between .000 and .005 inch).
This "running deeper through the quartz" can be caused by the fact that quartz is "weaker" against acids than felspar (I suppose he means feldspat
or feldspar). The other observations also can be an indication of the effect from acid.
His white cotton thread showing the helical nature of the groove looks to me as a very rough measuring method, which is not easily underwritten by
observing his posted photographs on that page. To me the grooves seem to run in parallel circles above each other.
I can only be sure when I have that core in my own hands.
The only logical reason I can bring up to still adhere to my theory, if I subscribe to the conclusion of a helical groove on that core by Chris Dunn,
is some sort of later "machining" of an etched out granite core. The reason for that is beyond my grasp however.
Directly after breaking out of the core from its seat in the granite block by the ancient egyptian stone worker, this "machining" then used some
sort of slow "lathing" method to smoothen up the surface of the core.
I know that when you lead a modern steel cutting tool too fast along a piece of clamped in, fast spinning steel pipe, on a present day lathe, you will
end up with a rough carved out spiral on the surface of that pipe. You have to lead the tool very slow along the spinning pipe, to get a smooth
surface.
Next question, what kind of ancient method of carving can we imagine, which copies a modern lathe, without electro motors and steel tools etc.
That means at least in one option, that the granite core must have been rotated, while the used tool must have been lead along the rotating granite
core.
There's only one farfetched method I can imagine momentarily :
The core is clamped in a hole by means of one or more wooden or stone wedges.
Imagine a massive stone with a rough diamond or other precious stone embedded in it.
They can be found in multiple places near Egypt, I found a handfull of rough alluvial diamonds in Kenya, Niger, Benin, Togo, and stone embedded ones
in Eritrea, Somalia and Ethiopia, which I sold in Antwerpen. Yes, I am lucky to be still alive. The last 3 places were no fun at all to hang
around.
Hang that stone on a rope, and circle it around the clamped-in rough etched-out granite core, while keeping the rough diamond pressed against the
core. Crazy idea. Because the rope must also go down fast while circling, and I don't know how to achieve that with ancient techniques.
I saw the way the diamond cutters and grinders in Antwerp worked. They glue their work piece, a rough diamond, on a wooden stick, and push it then
against a fast revolving round steel plate with diamond dust glued on it. I don't think this technique was possible in ancient Egypt. No strong
enough glue?
Perhaps a rough diamond was clamped in some sort of other wooden or stone object?
I don't think the ancient egyptians had any kind of lathes. I can imagine a small stone disk with a groove around it, and a leather band around it in
that groove, and another much bigger stone disk with a groove around it, and that same leather band around that disk also, and some strong egyptian
guy spinning the big disk with a stick attached. That would let the small disk spin a lot faster.
And the famous granite core glued or clamped in the center hole which also holds the axel.
Then I have a fast spinning core. And then? Your guess as good as mine.
Last gamble : stick with diamond glued on top, press it with all your might against the fast spinning core, while also hanging with all your weight on
the stick, causing your hands to go fast down the core. That would give a spiral along the core.
But why go that complicated route, when you can use special sand, or dust from crushed precious stones and a lot of patience, to smoothen the surface
of that core, simply by hand?
You would never end up with spirals on that core, however.
If Chris Dunn is right in his observations of that core, then we have a damn difficult task to find a viable way for an ancient egyptian stone worker,
to obtain the observed effect on that granite core.
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