keith and naomi oliver | 1 Aug 01:10 2007
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question regrding teaching people to carve stone

Dear Christine,

Isn't it great to be apart of our discussion forum.
As to your question on a clay based stone, I was referring to the soft 
stone called Pyrophyllite( common name is wonderstone) another soft 
clay based stone is called
pipestone( the indian made peace pipe out of this stone)
Another easy to carve stone I and other carving teachers' use  as an 
introduction to stone carving material here is semi transparent 
soapstone.

I was supplied  with both the wonderstones and soapstones( always be 
conscious of the stone dust hazards with both these stones) by a 
canadian stone supplier  called NEOLITHIC STONE COMPANY.

My husband found them on the internet, have a look at the gallery of 
artworks , it shows the fantastic carvings
in all these stones by a variety of  carving artists .
As an advert plug for Randy the owner of this company
( fantastic person) he also supplies , limestones& marble
 stones that you could use with your carving students.

Christine I would not use a bansaw on limestone or alabaster, just use 
these for cutting up the softer stones, when doing the introduction 
sculpture.

We use a large pruning saw on the limestone, in the cutting out phase.

On another tack I was producing an eye( to inlay for a very small 
wonderstone sculpture ) using white alabaster, 3 broken eyes later ,
(Continue reading)

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Re: Namoi's sandblasting questions

RE: "...to use a sandblaster"
Hi Naomi,
Sandblasters require a fairly large CFM output from the compressor. There are basically two types of
sandblaster — the most common and least expensive is the gravity-fed siphon type, which uses the suction
of the air through a tube to siphon the abrasive particles out the bottom of a holding tank. A sand blaster
like this requires about 12 CFM to operate efficiently when using a fine grit blasting medium (medium grit
and coarse grits require more). My 60 gallon, 5HP single-stage compressor supplies about 9.5 CFM, so when
blasting I have to use it for perhaps twenty minutes with the compressor running continually to try to meet
the demand — when the pressure gets too low I have to stop work and let the compressor build back up to full again.
The second type of sandblaster uses a pressurized tank in which the blasting medium sits. These are perhaps
about three times as expensive as the siphon-fed type, and they also expend the blasting medium much more
quickly than the siphon-fed type. But because they pressurize the tank with the blasting medium in it they
don't require as high a CFM from the compressor. However, they provide a much more efficient
cutting/abrasive action, doing in five minutes what might take twenty or thirty minutes with the
relatively inefficient siphon-fed type. Google the Italian stone sculptor Francesco Somaini who uses
this type of sandblaster to carve his marble forms instead of a traditional hammer and chisel.
The most common abrasive medium is the namesake: sand — but not usually simple beach sand (which has
particles that are rounded-off in shape). Sand made from crushed quartz will retains sharp edges to the
faceted surfaces and provide a much more efficient cutting action, especially on harder materials
(quartz is about 6.5 to 7 on the Moh's scale). Beach sand can be used, but at the expense of a degree of cutting
action. Other blasting mediums are synthetic abrasives like silicon carbide, various sizes of
steel-shot, and walnut shells. Each type of abrasve provides particular qualities in the results — for
instance silicon carbide (about 9 on the Moh's scale) would be used for extremely hard materials (i.e.,
for jade — which can be up to about 7 on the Moh's scale), where steel shot medium will clean surfaces
without digging-into or below the surface as much. Walnut shells are used to provide a 'sheen' on metal
surfaces rather than providing cutting action. 
Good blasting to you,
Don
www.dondougan.com 

(Continue reading)

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Re: Namoi's sandblasting questions

Hi again,
Forgot to mention that because my sandblaster/compressor set-up is so relatively inefficient I use
sandblasting mostly for cleaning and texturing of surfaces rather than 'carving' as such, though with
crushed sand or silicon-carbide abrasive it will cut into the stone if I am patient (most stonecarvers
are, right?).  
I know a guy who works in primarily in sheets of thick plate glass, etching/blasting elaborate designs with
the use of rubber sandblast resist stencils.  Most of his designs are up to about half-an-inch deep (12mm)
in three-quarter-inch (20mm) thick glass.  He uses only the pressurized-type blaster, and he thinks my
siphon-fed rig is really wimpy . . . ! <grin> 

Wimpy, aka Don 
www.dondougan.com

 
Bernard Arnest | 1 Aug 05:23 2007
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stone fell; damage of impact?

Hi,
       The tombstone I was working on tipped over; it was on a wooden table,
so the base moved not at all, and the top point fell 37".  It's in one piece
alright.  I haven't had the chance to start carving again; but what are the
risks of microfissures affecting final polish, or worse, opening up to real
cracks that could *actually* break it?
        Someone mentioned once that the blasted pink marble in maryland
(limestone?) has hairline faults that don't really affect strength, not for
carving, but do show up when you polish it as white lines.  If that's what
blasting does, then maybe simply tipping over, it should still be sound?

                   thanks!
                      -Bernard

 
blb | 1 Aug 06:16 2007
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Re: Namoi's sandblasting questions

Thanks for the nice rundown, Don. Another type of sand I found when I  
dabbled in sandblasting is garnet sand which they claimed was good to  
use because it doesn't have silicon in it and is thus a lot safer to  
use. Definitely double check this though, I could be way off!

If it didn't take such a major shop investment for safety, I would  
find sandblasting a really useful tool.

It just occurred to me that Naomi should consider the feasibility of  
a frosting or bushing chisel which also can be used to carve  
recesses. But for inlay work you'd have to figure out how to make a  
clean edge.

Bill

blb | 1 Aug 06:26 2007
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Re: stone fell; damage of impact?

On Jul 31, 2007, at 8:23 PM, Bernard Arnest wrote:

> what are the
> risks of microfissures

a simple topple shouldn't cause any fracture in a massive stone, but  
it may open an existing crack. Use the wet technique to see if there  
any open fractures. Spray water on surface and watch it dry. An open  
crack will dry last. (Complex stone like serpentine is another story).

Base on a few headstones I have seen, I wouldn't expect there to be  
any microfissures unless it has undergone some unusual distress.

Bill

 
jennifer cull | 1 Aug 06:35 2007
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sandblasting

Hi Don and all,
Been super busy with shows and trying to keep up, but I was reading what Don
said about sand blasting and I have the same set up as he does.  The 5 horse
power compressor and the cheaper blaster.  I haven't done any in years, so
many years that I can't remember what I did about the sand blasting area.  I
want to retain some of the sand if possible because it's not really sand but
tiny beads of something or another that's harder and more expensive.  I
remember my arms getting blasted as well as the piece,  and I had taped off
the area that I didn't want touched.  Does anyone have a Mickey mouse method
of retaining the sand?  Or as some people call it, "Jerry rigged" , which
all adds up to cheap, do it yourself type of dealing with problems.  Only
thing that comes to mind is a large cardboard box for starters, but the
technicalities of the set up elude me.
Thanks for any help anyone can give. 

jennifer cull | 1 Aug 06:40 2007
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Re: Namoi's sandblasting questions

Hi bib,
I find the frosting chisel to be really crude in comparison to sand blasting
  Just finished trying it and was not happy with it at all. Hope to get some
advise on my blasting set up that might help other too.
-------Original Message------- 

From: blb 
Date: 7/31/2007 9:17:05 PM 
To: stone@... 
Subject: [stone] Re: Namoi's sandblasting questions 

Thanks for the nice rundown, Don. Another type of sand I found when I 
dabbled in sandblasting is garnet sand which they claimed was good to 
use because it doesn't have silicon in it and is thus a lot safer to 
use. Definitely double check this though, I could be way off! 

If it didn't take such a major shop investment for safety, I would 
find sandblasting a really useful tool. 

It just occurred to me that Naomi should consider the feasibility of 
a frosting or bushing chisel which also can be used to carve 
recesses. But for inlay work you'd have to figure out how to make a 
clean edge. 

Bill 

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Unsubscribe & other options: http://www.freelists.org/list/stone 
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CHAS BODDEKER | 1 Aug 07:23 2007
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Re: Namoi's sandblasting questions

Aluminum oxide is another blasting abrasive; but , expensive. A couple of advantages in using garnet
instead of silica sand are the facts that sand becomes rounded in the blasting while garnet breaks to form
newer sharp pieces , albeit smaller; and  less dangerous dust is produced by garnet.Silica sand dust can be
extremely harmful.
  ----- Original Message ----- 
  From: jennifer cull<mailto:jennifercull@...> 
  To:
stone@...<mailto:stone@...> 
  Sent: Tuesday, July 31, 2007 9:40 PM
  Subject: [stone] Re: Namoi's sandblasting questions

  Hi bib,
  I find the frosting chisel to be really crude in comparison to sand blasting
    Just finished trying it and was not happy with it at all. Hope to get some
  advise on my blasting set up that might help other too.
  -------Original Message------- 

  From: blb 
  Date: 7/31/2007 9:17:05 PM 
  To:
stone@...<mailto:stone@...> 
  Subject: [stone] Re: Namoi's sandblasting questions 

  Thanks for the nice rundown, Don. Another type of sand I found when I 
  dabbled in sandblasting is garnet sand which they claimed was good to 
  use because it doesn't have silicon in it and is thus a lot safer to 
  use. Definitely double check this though, I could be way off! 

  If it didn't take such a major shop investment for safety, I would 
  find sandblasting a really useful tool. 
(Continue reading)

Bernard Arnest | 1 Aug 14:32 2007
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Re: stone fell; damage of impact?

Thanks!  That's reassuring.  It did fall flat; not on one corner or
anything, and the surface was --compared to concrete, at least-- pretty
springy.  Though not quite as good as had it fallen on the ground.  I'll
spray some water on it.

                                 thanks again!
                                   -Bernard

what are the
> risks of microfissures

a simple topple shouldn't cause any fracture in a massive stone, but
it may open an existing crack. Use the wet technique to see if there
any open fractures. Spray water on surface and watch it dry. An open
crack will dry last. (Complex stone like serpentine is another story).

Base on a few headstones I have seen, I wouldn't expect there to be
any microfissures unless it has undergone some unusual distress.

Bill

 

Gmane