Francisco,
There are portable black light units, designed for jewelers, which I
have found useful for detecting some forms of restoration and fakery.
Ciao,
Scott
-----Original Message-----
From: Conchologists List [mailto:[log in to unmask]] On Behalf Of
Francesco Guarracino
Sent: Wednesday, December 29, 2004 4:23 AM
To: [log in to unmask]
Subject: Re: fake shells
Dave,
thank you for your kind, long & detailed reply.
Does anyone use "black light" or other technology to detect doctored
shells?
ciao
Francesco
On Mon, 27 Dec 2004 01:10:09 +0000, DAVID LUM <[log in to unmask]>
wrote:
>Hello, Francesco,
>
> As a cowry and cone collector, I've come across quite a
few 'doctored'
>shells and have learned some ways to figure out the authenticity of
shell
>features. I hope you will find these methods useful:
>
>- Painted shells - The painting techniques used to 'restore' dead or
>otherwise poorly patterned shells is getting increasingly sophisticated
and
>professional. One method I was quite impressed with is the layering of
>paint and clear or translucent resin to produce depth in patterns, much
like
>you see in genuine cowry shells. A magnifying loupe is useful in
detecting
>unnatural looking brushstrokes or paint dabbling, but if you have a way
of
>making a high resolution scan of the shell, you should be able to
readily
>identify manipulated patterns, bubbles, or other problems. I have used
the
>scanner method to identify faked shells I have received in the mail and
had
>them returned for refund.
>
>- Tapping - light tapping of a highly glossy shell surface such as that
of a
>cowry shell against your front teeth can expose a resin overcoat. A
genuine
>shell surface should give a crisp tap, while a resin-coated one might
feel
>dull.
>
>- Look for continuity in ridges and growth lines - Cones and voultes
are
>very often filed, and sometimes the workmanship is such that it is
nearly
>impossible to tell whether filing has been done or not, especially if
the
>lip is very sharp. One way to check is to look for the growth lines
along
>the lip. The lines should be continuous from the anterior to the
posterior
>of the lip. They should not terminate abruptly part way.
>
>- Layers - In species where a mantle covers over the shell and shell
>material is laid down over time, a layering effect occurs. These
layers
are
>not apparent in a perfect shell, as the upper ones obscure the lower
ones.
>However, if any cutting into the shell has occurred, you can see the
>layering. As a recent example, I obtained what looked like an
exceptional
>Cypraea mauritiana with a corrugated (scalloped) base. I have read
accounts
>from very reputable shell dealers that they have seen live animals with
such
>a base, so I decided to purchase the shell. Later, upon inspection in
>bright sunshine, I saw the telltale layering I referred to above. With
>further inspection, it was also clear that some of the corrugations
were
too
>finely and sharply cut to be natural. The polishing done on the
surface
was
>perfect and it didn't even appear that any kind of coating was used.
>
>- Chemical test - Solvents, such as acetone, can be dabbed on a
suspected
>spot to detect resins, which would dissolve or become cloudy.
>
>- Baked shells - Sometimes it's more than obvious. For more carefully
done
>work, look under a magnifier for microcracks and nacre bubbles.
>
>- Sun-bleaching - For glossier shells, sometimes you'll get nacre
bubbling
>and a dulling of the finish. Also, carefully look within the aperture
of
a
>shell to see if there is darker, inconsistent color further inside.
>
>- Black light - I've never used this myself, but it makes sense that
any
>resin or filler used on a shell should show up as a visual
inconsistency
in
>the shell.
>
>- Too perfect - Truly Gem shells are very rare if one follows the HSN
>grading standards in a strict manner. It's hard enough to get cowries
in
>true Gem quality, and I really do not believe in Gem Murexes. Anyways,
if a
>shell looks too perfect and has too exceptional a feature (size,
appendage,
>coloration, pattern, etc.), it's time to be cautious. Also, if certain
>parts of a shell look much too perfect to suit the overall quality of
the
>shell, there's a good possibility of manipulation.
>
> This is just my two cents on the subject. I'm sure we can all
learn
>plenty more from others.
>
>Best regards and aloha,
>Dave Lum
>
>
>>From: Francesco Guarracino <[log in to unmask]>
>>Reply-To: Conchologists List <[log in to unmask]>
>>To: [log in to unmask]
>>Subject: fake shells
>>Date: Sat, 25 Dec 2004 18:14:56 -0500
>>
>>Dear friends,
>>
>>All we know that quite a lot of "enhanced" shells (mostly cowries
and
>>conidae) are on the market or in private collections of cheated
>>collectors: painted, coated, baked, repaired, polished shells, and
so
>on;
>>e.g., recently somebody talked about cypraea aurantium treated with
acid
>>and then polished; some years ago even Raybaudi was wrong in
considering
>>the specimens of the so-called cypraea lobettiana.
>>My question is: how do you detect a fake shell? How can you
discover
if
>a
>>shell was baked, or discoloured under the sun to make it an albino?
How
>>can you find out the result of Shell Doctors' art? It would be very
>>interesting to know more about methods of discovering frauds: any
>>suggestion and/or opinion?
>>
>>All the best
>>Francesco Guarracino
>>Roma - Italy
>>
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