Creating holes in stone
Eventually every sculptor wants to punch a hole through their stone.
It's only natural.
Note, however, that the simple act of making any hole greatly reduces the strength of the
stone in the area around it.
If you then continue with the hammer and chisel on other parts
of the sculpture the chances of breakage in the area of the hole go up dramatically.
To help
avoid that, it is best not to create the full hole right away.
You can start it - from both sides
of the stone - and carve enough out so you clearly know where it is and see what it will look
like, but stop before going all the way through.
The strength difference between a hole and
a depression with half an inch of stone remaining to be removed is quite large, and your
carving will be much less likely to break while you work on it if you remove that last bit of
stone - called a bridge - at the very end.
Once it's gone you should only use files; no more
hammer and chisel work.
Actually creating a hole with chisels is a matter of working with the narrowest toothed or
flat chisels you have and working from the center of the hole out.
Work all around the outer
edge in a circular pattern, going deeper as you can.
Eventually you'll be unable to remove
any more stone from the bottom of the hole because the sides get in the way of the
chisels.
At that point you have to widen the hole more before you can go deeper.
13 Power tools, of course, change the entire process, but (as stated above) we don't
recommend using power tools early on.
See the power tools section later, though, if you
feel you're ready to use them.
Carve along cracks, not across them
Every natural stone has flaws, and some of those flaws manifest as cracks or fissures.
When carving, it is best - particularly when near your final surface - to use chisels along the
direction of the crack if possible, instead of at right angles to them.
Any crack - even if it
doesn't significantly weaken the stone - is a place where the stone on one side of the crack
is not well bonded to the stone on the other side.
Your carving will tend to chip off tiny
flakes on either side of the crack, making it more difficult to polish smooth.
This problem is
more significant in softer stones.
To avoid it as best you can, the first thing to do is avoid using chisels at right angles to the
crack when close to your final form.
Chisel use puts more stress on the stone than files or
sanding, and is therefore more likely to keep the crack visible.
If you can use files - also
along the direction of the crack if possible - you'll reduce the problem.
What to do if your stone breaks
Stop!
Immediately.
You may be able to glue it back together with an epoxy (see the
detailed section below) but it will be less obvious if you carefully gather any little chips and
make sure they are glued back in during the process.
This isn't something you're going to
undertake for a small error, but if your entire stone breaks you have little choice but to glue
it back together or completely rethink your sculpture.
Also, take note of the actions you
were making when it broke.
Were you hitting harder than normal?
Were you working on or
near a crack?
Was the stone very thin in the area of the break?
Had you created a hole in
the piece, weakening it?
Note these things so you can avoid causing similar problems later.
It is also important to know this happens to every sculptor.
Even experienced carvers find
stones with hidden flaws that cause things to break.
This can be minimized with experience
and care in your tool use, but sometimes it simply cannot be avoided.
Stone is a natural
material and contains natural flaws.
Be prepared to redesign your sculpture in the event of
a break.
Or abandon it altogether and start something else.
Information from: http://www.bangtherockstogether.com/docs/How_To_Carve_Stone.pdf
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