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Grinding, sanding stages for carving


#1

Hi I hope I can get some help from a carver. I have been given two
large pieces of rutilated quartz. The owner wants all the surface
ground down, sanded and polished somewhat close to the natural shape.
(less all the bumps) I have the rough grinding finished. I used my 50
grit eight inch grinding wheels. I can then use an 80 grit, 100 grit,
220 grit metal wheels. (All 8 inch.) For sanding I have an 8x3 inch
rubber drum. I have a 100 grit belt, a 220 grit belt, a 320 and a
600. I have done smaller pieces of similar material but these pieces
are from 1 to 2 pounds. (I am guessing) The surface area is quite
large with some inside (Concave) curves.

Here is my problem. When I miss a spot with one step, it takes so
much more time with the next stage. I usually just go back over the
whole area again with the coarser grit wheel. It seems that there
should be some way to mark the material so that I could see where I
have ground so I would know when I have covered the whole area
without leaving places that I have not covered. What is that process?
The material I am working on is water clear rutilated quartz. Just
about all the fractures are grounded away but I don’t want anything
to mark the outside that would get in any hidden crack or fracture. I
also would not want to permanently stain inside the surface.

What do carvers use for something like this? Where can I go to do
some research? I will start to do some looking on my own tonight as I
want to be able to get these pieces finished for the owner.

Thanks for all help.
Larry


#2

I am not an expert, but I think probably the best thing to use would
be an aluminum wire. This is used when polishing a surface on a flat
lap to make sure it is completely ground down. It will touch only the
existing surface and not get into the cracks. The only possible
problem I see is if the ends of the rutile that protrude are little
holes that would perhaps catch the point of the wire and chip out. Rose
Alene McArthur @O_B_McArthurs
(where the snowplow just drove by)


#3

Use a large sharpie pen, black. Cover the material before you begin
and as you cut you’ll remove the black enabling you to see any places
you’ve missed.


#4

Hi Larry,

I sometimes use a copper pencil to mark areas in a stone so that you
can see which have been ground and which have not. A brass wire brush
also works. You can make your own wire brush marking pencil by
snipping off the springy brass wires from an old brush, then inserting
the wire bundle into a length of 1/8" copper pipe and banging it shut
with a hammer.

Cheers,
Hans Durstling
Moncton, Canada


#5

Hi Larry,

I’ve never tried this on large pieces of rutilated quartz, but it
works on smaller pieces of most everything else. I suspect it’d work
on rutilated quartz.

Use a wide tipped waterproof magic marker (a Sharpie would probably
work) to ‘paint’ the entire surface. An areas where the ink is visible
hasn’t been touched. If the wheel being used is coarse, you may have
to apply the coating more than once.

Dave


#6

Larry, a common way to be sure you have ground/lapped an entire large
surface is to run a black laundry marker pen across the surface from
end to end. Some people cover the entire surface. Of course, this is
not a good idea on porous material but quartz should be no problem
even if the rutile has come to the surface. This os used when
lapping bookends, geodes or other large flat pieces. After
grinding/lapping just look at the surface…if there is any black
showing you do not have a flat surface.

I’m not sure how you are getting a true flat surface using 8" wheels
though! Usually when doing such large surfaces, a vibra-lap is
employed. You can get a nice flat finished surface by hand rubbing the
stone on a piece of plate glass with grit and water. Polish can also
be done by hand with cerium oxide on a piece of damp leather glued to
a block of wood. Be sure to add a few drops of apple cider vinegar to
the slurry.

Cheers from Don at The Charles Belle Studio in chilly SOFL where
simple elegance IS fine jewelry!


#7

Larry, if you want to end up with large flat surfaces, your best bet
is to use a cast iron lap with loose silicon carbide grit. This is the
fastest way. Using the drum wheels you are talking about will result
in dips and indentations that are not obvious until the next stage
fails to remove them. If you have concave surfaces to work, the tool
will have to be smaller in diameter than the radius of the concave
part. There is nothing wrong with your combination of wheel grits,
just the wheels.

The least effort required would be to use a vibrating lap to get the
flats down. It takes a long time to do but you don’t have to be with
it every minute.

For marking the material to see where you have been and where you
need to go, I use a sharpie marker.  cover the entire surface you
are working then use a fine sand paper, 600 or so, on a hard
board  and do a quick light sand of the surface.  This will
take off all of color from the high spots and leave the pits,
scratches, holes, etc. that you will need to work out.

One more point, watch the heat buildup, especially during the polish
stage as you can easily pop the quartz. You have a lot of thermal
mass to work and it is very easy to get the surface hot and cause
cracking.
Don


#8

Hi Larry.

I might suggest using the (admittedly slower at removing material)
100 grit over the coarser grits for two reasons:

  1. The rougher grits will leave gouges of varying depth and the
    deepest ones become painfully obvious when you have refined the
    surface with the next smaller grit. Beginning with a finer grit means
    the deepest gouges resulting will be relatively shallower and will
    require removal of less material.

  2. Chatter from these coarse wheels can deepen existing flaws or
    encourage development of internal stresses which may cause heart
    failure when the process of carving approaches the area and releases
    the stress.

Lapidary Journal ran an extensive article on quartz varieties by Si
and Ann Frazier (1999 or 2000) which included about
working with it. I couldn’t find it on their site
http://www.lapidaryjournal.com but you might try the Lapidary Journal
Article Index for those years. The site has a list of references
which may include what you’re looking for.

LJ has also has had articles on gemstone (including quartz) carvers
such as Glenn Lehrer and Lawrence Stoller who collaborated on very
large items. These articles touched on some of the inherent problems
they had to overcome. Both artists are members of the Gem Artists of
North America (GANA). www.gemartists.org

Here are the URL’s for Lehrer and Stoller on the GANA site:

http://www.gemartists.org/glenlehr.html

http://www.gemartists.org/Lawr.html

HTH (hope this helps)

Pam Chott
Song of the Phoenix


#9

Larry

I haven’t worked with pieces that big but you coiuld just use the
aluminium marking pencil across the scratches. A method without
marking is to always sand in one direction for the same grit and then
90 degrees out for the next stage - th eloupe will show missed areas
well. Of course if the shape isstrange this method will drive you
crazy! Have fun!

Andy Parker, Agate House Lapidary
Ulverston, Cumbria, England
@Andy_Parker
www.agatehouse.co.uk
Tel: 01229 584023


#10

You should have done your grinding using a flex shaft and appropriate
size wheels to confrom to the shape of the stone,rather than force the
stone to fit your 8" wheel.Then your sanding and polishing done the
same.You could also have used a sand blaster to grind,sand and polish
and absolutely preserved the natural shape.These methods would have
kept the stones larger also.You can finish it now using the above
methods,or use a flap device.Take a brass dowel,split it up the center
on one end,use a flex shaft or mount it in a collet on the end of a
1/4 or 1/3 horse motor,helps control to have a foot reheostat for
variable speed,and hold the stone in your hands into the flap
device.Cut strips of sandpaper,or for the polishing leather,insert
them into the center cut of the dowel.They will flex to the shape of
the stone.You can also finish the job more effeciently by using
Diamond compounds.In fact,the whole job could have been done equally
fast and to perfection,if you used no motors at all.Just do the whole
thing by hand using sheet sandpaper,and muslin or leather to carry
sanding and polishing agents.To examine the stone for missed
spots,get the strongest power Optivisor.There are chalks and carbons
you can also buy in the woodworking industry that spread on the stone
will reveal crevices,low areas. The way you did it,your crystals likely
now look more like irregular tumbled stones.Check out these photos of
a 22kg Aquamarine recently done using the above methods.It was
originally covered with an orange rust.It is highly polished now,and
you cannot tell man had a hand in it.Totally natural looking,we
preseved the perfect Beryl shaped outside ring and even some small
attached minerals,like a mica/argonite formation,and calcites and
small Quartzes.Collectors value these included minerals.
http://www.LICCINI.com/CoverAqua2/GalleryAqua.htm Mark Liccini
http://www.LICCINI.com