Polishing granite columns

[Simon Brown <moonsong@zzzzzzzzzzzzzzz>]

Peggy and Pat Perazzo's 'Quarries' page in the CAGenWeb site hosts a
collection of stone documents www.cagenweb.com/quarries

An interesting article I've been studying concerns the latest methods in
polishing granite columns. That is, up-to-date in 1884. I found the
article by clicking on Stone Carvers/Stone cutters 'Methods' , then
scrolling down to 'How Granite Columns Are Polished'.

The page featuring the article is number 59 of 288 pages scanned by the
Cornell University's 'Making of America' digitising project.

The technique concerns granite columns worked to shape by hand and air
tools, mounted on a lathe and rotated backwards against cast iron blocks
pressing on and against the rough surface. Honing and polishing is done
in a 3-step process. Beach sand and water is used as an abrasive to
grind out the tool marks, followed by a mixture of emery grit ranging
 from grades 40 to 60. Polishing is carried out by similar blocks with
felt on their faces, and tin oxide (putty powder) applied until the
surface shines like a mirror.

What is interesting to me is that the emery abrasive is not changed or
added to, but the slurry formed by abraded granite, degraded emery and
water carries out the entire honing process under pressure from the
blocks and the turning stone.

The process has been replaced today with diamond technology, but I
wonder if the polish produced today matches the depth of shine achieved
by this comparitively primitive method 120 years ago?

Simon