Re: [MV] DMV inspection

Alan Bowes (inbox@todacosa.com)
Sun, 07 Jun 1998 20:42:07 -0600

You can often obtain a VISIBLE image from the acid etching method. We
have used this method many times to help identify ancient, worn-out
coins. The acid tends to work faster on the edges of the grains in the
metal, and where the metal is less compacted and the grains/crystals
less distored, the acid will work at a slightly different rate. This can
often create a faint, but readable image when the technique is done
correctly. This technique works well on coins that were
hammered/stamped, which is analogous to stamping the numbers in the
frame rail.

This method will not appreciably damage the frame. Only a very thin
layer would be affected. That said, if you select the wrong acid or
strength and leave it on too long, there is some potential for etching
it too deeply, but if you're following directions, there should be no
problem.

IF you're interested in pursuing this, I'd suggest checking out some
works on archaeological lab and conservation methods, as there are a
number of different techniques and chemical and optical combinations
that could be employed, depending on the type of metal/alloy, the size
of the object, whether you have a horizontal surface, whether you can
use ultrasonics, etc.

You would probably have to reapply the acid solution numerous times,
since you can't very well immerse the frame in a lab tray.

You might also want to smooth the ground-off area a bit to remove most
of the grinding marks, so that the slight texture would show up better.
Viewing is usually best in a dark room with an oblique, point light
source (unless you have a vertical-illumination microscope that is set
up for viewing metal grain structure, but few of us have some exotic
things lying about the shop).

I don't have the appropriate books at my disposal at this moment, but if
you can't find anything on the topic, let me know, and I'll look up a
few sources of information for you next time I'm at the university.
There are a lot of possibilities if you like to experiment with this
stuff.

Alan

Robert G. Riddell wrote:
>
> On Sat, 06 Jun 1998 14:00:26 -0700 King <landy@netpointer.com> writes:
>
> >>An x-ray will do the same with less damage to the frame or
> >surrounding area.
> >Andre
> >
> >
> Your alternative is unusual. I'm not sure if DMV would find it
> acceptable though
> since it wouldn't provide an actual display of the number on the frame,
> just the X ray photo.
>
> Rob
>
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