hardness of black marble . . . diamond handpads

Quoted text begins.RE: gradation scale for marbles . . . thats lists the different popular
marbles and their hardness relative to each other? and (diamond)
handpads....do they wear out quickly?
End of quote.

Justin;

It sounds like you are well on your way to finding out about the
different hardnesses of the types of stone. In the end what is most
important, is how it works for you. I have found that sometimes the
'hardness' of a particular stone makes it easier to work ? if you have
the right tools and approach.

What I mean by this is that I try to use the nature of a particular stone
in such a way that the form I make out of it makes 'sense' with all its
inherent qualities. I tend to do this in a very intuitive manner (ie.,
using experience as a guide, I modify my approach to what 'feels' right
in the particular piece). Experience is the key. Until you have tried
a number of stones, experiencing their unique qualities through working
with whatever tools you choose to use, you will not have that necessary
broad sensory knowledge-base to judge with.

Now, having said what probably seems like a Catch 22 (like a dog chasing
his own tail), there are some sources for guidelines you might use to
guess how something will react to your tools and working methods. One
such resource is listed on the 'bibliography' page of my website, which I
have pasted below the text of this e-mail. The third paragraph (in the
descriptive text following the publication info) describes the engineer's
test data used to classify the stone, and where it is quarried, etc. The
dry numbers will tell you little about the working properties until you
have worked a few of the listed examples and have a feel for what the
differences in the numbers mean to your tools and your hands (if, like
me, you did NOT get a degree in engineering and are JUST a sculptor ;-)
who mostly just looks at the pictures. (seriously, being a real
scrounger and getting old stone from all sorts of sources long after it
has left the quarry, I use the images to help me identify types of marble
I am using).

The price of this publication is about the same as a couple of dozen
carving chisels, so it is a hefty investment. If you are trying to find
out about some specific stones, a free on-line source that might be of
some help is http://www.findstone.com
On this site you can see fairly good quality images (depending on your
monitor's resolution) of different types of marble, and some of the
classification info. The site (like the publication noted below) is used
primarily by non-carvers who are more interested in countertops, floor
tiles, or architectural functions than in the working or carving
properties of the material.

There are many printed resources In addition to these, a few of which I
have found useful are listed on my website. You can also 'Google' and
find a large number of references online ? I find new ones every time I
get on line to do some research.

Generally I have found that the darker, more colorful, and more
highly-veined marbles are more difficult to work than are the more
uniform, lighter-in-color varieties. Difficulty in working is not always
because of hardness ? sometimes it may be brittleness, or a tendency to
split along color lines, or the toolmarks and working bruises are
hard-to-remove. That said, there are exceptions to my general statements
in both directions!

Rather than searching for particular types of stone, perhaps one of the
best approaches I have found is to become familiar with the varieties
that are most readily available (to you). This approach gives an
experience-base for determining relative working qualities, which can
then be used in testing new varieties you might want to work. Then, when
you come across a chunk of stone that someone wants moved out of their
backyard or their old building, you can determine whether it is worth
your time and effort to say "yes."

I also never reject any kind of tool as a possible solution to a working
problem . . . be it expensive diamond or a piece of scrap material,
antique hand tools from the flea market or a new powertool from an
industrial supplier. The diamond hand pads work for a good while even on
hard stones. I can't tell you exactly how long, because I don't always
use them on every sculpture ? sometimes I can sand/polish with better
economy using power tools (depends on the design of the piece).

The working-methods that prolong the life of the pad are: use with water
to lubricate/cool the pad, use light pressure and let the sharpness of
the diamonds do the work (don't press hard), and use the full range of
grit-sizes every time ? don't skimp on elbow grease or skip any grits
like you might have found worked fine on alabaster (on hard black marbles
you don't want to skip ANY grit ? scratches from the coarse grits will
show up at the final polishing stage).

The finer sanding and polishing pads seem to wear out faster for me than
the coarse ones ? but perhaps that is because during the rougher stages I
can often use power sanders instead of the coarse handpads, but have to
use the finer ones for detail where the powertools do not allow the fine
control I want at the conclusion of the polishing process. If you don't
use powertools at all the coarse ones will need to be replaced more
often.

Good Carving to You,
Don

http://www.dondougan.com

DIMENSION STONES OF THE WORLD Volumes I & II
Robert Hund (author & editor), Ronald Busse
1990-93 - Marble Institute of America - loose-leaf, 553plus pages

This open-ended reference work consists of two loose-leaf volumes, worked
on by numerous teams led by the directors of the Marble Institute of
America over a number of years. Because it is loose-leaf, it is/was
enlarged by the addition of supplementary pages printed and available to
the purchasers in following years. The original two volumes contained
examples of 518 stones - 180 granites, 138 limestones, 163 marbles, 15
travertines, and an assortment of 22 examples of onyx, quartz-based
stone and slate. The original 518 examples are referenced by four
different indexes: by color range, by producer, by type of stone, and by
a cross-reference of names - the supplementary pages are not indexed.
There are also 6 pages of the same text in each volume describing common
terms used in the trade, standards for testing values, and geological
classifications in addition to the table of contents and credits to the
teams.

The primary subject of the two volumes set (and possible later volumes)
is a series of life-size full-color reproduction plates (7¾" wide x
8¼"high) printed on glossy 8½" x 11"stock, and above each example is a
coded label number which gives the type of stone classification.
On the reverse of each page there is a standard information form for each
example - containing the primary name, other trade names, type of stone,
country of origin, quarry location, geological formation, color range,
any additional description, int/ext usage, technical values as to
absorption, density, compressive strength, abrasion resistance or
hardness, flexural strength, MIA classification for soundness (marble
only), and the source of both the color plate and all information
(usually the company owning or operating the quarry).

I purchased my copy directly from the Marble Institute of America in the
early nineties, and received two updates in the mid-1990's, each update
with about half-a-dozen additional loose-leaf pages of granite,
limestone, or marble examples.

Marble Institute of America
30 Eden Alley Suite 301
Columbus, Ohio 43215 USA

phone: 614.228.6194
fax: 614.461.1497