Oiling stones

While we’re on the subject…how does one oil a stone? Mark
Liccini had an article on a lapidary page but I couldn’t
understand the process as it was porrly explained. Does one
vacuum a beaker of oil with the stone in it or do you use air
pressure to force it into the stone? If you have a crack in a
quartz cabochon is it possible to oil it and make it disappear?
Questions, always questions…Dave

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I received a very simple process from an old salt a while ago.
You take a small orange juice bottle or canning jar and place the
oil in it covering the stones. Place the bottle in boiling water
and heat it for 20 minutes or so. Cap the bottle while in the
water (carefully) and remove it to cool down (creates a vacuum
inside the bottle). You will see the button on the bottle (or
jar) cap suck inward creating a vacuum. Leave it out of the
water for an hour or three until it cools completely. Next take
the bottle and put it back into the boiling water (actually place
it in the water and bring it to a boil) and let it boil away for
30 minutes to an hour. This creates pressure inside the bottle.
Between the vacuum effect and the pressure, you will have a
pretty well oiled stone. However, if you really want it done
right, find someone with a vacuum casting unit and do it in

Frank Russo

  ....how does one oil a stone? ...(a person)... had an article
on a lapidary page but I couldn't understand the process ...
Does one vacuum a beaker of oil with the stone in it or do you
use air pressure to force it into the stone? 

G’day Dave; my suggestion is to put the flawed stone in a small
vessel together with the warm oil / opticon (or whatever.)
Subject the vessel to as good a vacuum as you can manage. Let
the air in after a few minutes… Repeat the evacuation. etc The
idea is that when you subject the stone to a very low pressure
some of the air in the crack will come out. When the pressure
returns to room value, the pressure of the atmosphere (14.75
pounds/ sq. inch) will force oil into the crack. Repeating this
more than once will help to really fill the crack with oil. Thus
you are subjecting the stone to both vacuum and pressure.
However, the refractive index (light bending power) of the oil
must be as near as possible to that of the stone, otherwise the
crack will be visible.

I used to demonstrate to certain undergraduate classes at a
University. One of the experiments was concerned with refractive
index (RI). I dissolved chloral hydrate in a special liquid,
using a glass rod as a stirrer. As this demonstration was done
using a projector, the students were able to see on the screen
that the glass rod became less and less visible as more of the
chemical was added until the rod completely disappeared when the
refractive indices of the glass rod and the liquid were
identical. Incidentally that solution is used to prepare
specimens for mounting in microscope slides for the same reason.

When transparent gemstones are tested, one method of determining
refractive index is to put them into certain liquids with known
RI values. When the edges of the stone are hard to see, the RI
of the stone and the liquid are very similar. These days it is
done with a refractometer which actually measures the angle to
which the light is bent by the stone. More than you ever wanted to
know about oiling stones! Cheers,

       / /
      / /      Johnb@ts.co.nz
     / /__|\
    (_______)  In sunny temperate Mapua NZ -

Autumn’s here

Okay I am jumping on the band wagon late with this one. How can
you tell if a stone you purchased has been oiled without
destroying the stone? I recently went to the MJSA show several
weeks ago and bought a ton of really nice stones (they were so
cheap! Has to pick them up). Now I am wondering if they were
cheap for a reason - like they are filled with oil.


Bill Ehney

DeDe, first question, what kind of stones?? Some types of
stones cannot be oiled, or at least nothing more than oiling the
surface to make them shine or allow you to see into them.

cutting quality has a lot to do with price. Perhaps the stones
were poorly cut , resulting in the cheap price.

Emerald comes to mind first off, could be oiled, or have
cracks filled in some other way.

Still first question has to be what kind of stones are we
talking about.