[NHCOLL-L:2283] Re: Appropriate Crack filler

[Jill K. Harris]

Bob,

I wouldn't use caulk, just because it's messy and will be fairly permanent.
I would cover the ethafoam forms you make with a black volara (a closed cell
foam).  We have some black volara that is 1/4' thick and use it when we
don't want the white volara or ethafoam to show underneath a specimen.  If
you do a Google search for Volara, many vendors come up.

Just my 2 pennies.  Good Luck, sounds like a labor intenstive undertaking.

Jill

Jill K. Harris
Registrar
Virginia Museum of Natural History
1001 Douglas Avenue
Martinsville, VA 24112
direct phone #: 276-666-8618
fax #: 276-632-6487
email: jillharr at vmnh.net


----- Original Message ----- 
From: "Bob Glotzhober" <bglotzhober at ohiohistory.org>
To: "NH Collection List Server (E-mail)" <nhcoll-l at lists.yale.edu>
Cc: "Gnidovec Dale (E-mail)" <gnidovec at geology.ohio-state.edu>
Sent: Tuesday, May 11, 2004 2:48 PM
Subject: [NHCOLL-L:2282] Appropriate Crack filler


> We have a very large (3-4 feet diameter) fossil stump from
Lepidodendron/Stigmaria that needs some conservation work.  It is quite old,
and without tearing apart the cabinet that contains it, I would guess that
the bottom of the stump was either concave, or at least had huge hollow
areas (rot during life?).  When it was originally mounted this space (which
is not visible from above) was filled with a fine, white sand.  The entire
fossil and its case into which it is embedded is at least 1000 if not 2000
pounds. Part of the weight is the fossil, part is the wood case, and part is
plaster that was poured around the fossil to make it conform to a
rectangular case bottom.  The bottom of the case is made up of thick oak
boards, each about 6-8 inches wide.  Unfortunately, over the years, some of
the filling sand seeped out of the cracks between the oak boards, creating a
hollow that eventually caved in.  Apparently years ago some of the cracks
between pieces were caulked -- which !
>  we will remove.
>
> The plan is to fill as much of the void as possible with a dense ethafoam
(to avoid the weight and other problems of both the sand and the plaster
which surrounded the specimen.  At the moment we do not plan to fill
whatever small voids exist between various blocks of ethafoam and the fossil
that we may end up, but to try and cut and fit the foam as much as possible
to support the pieces above.  Then we will piece back together the cracked
pieces of the surface of the fossil to form the top of the stump.
>
> This will undoubtedly leave some fairly large cracks -- some 1/4 to 1/2
inch wide we suspect.  We really don't want the white ethafoam below to show
and have debated methods to cover or fill the cracks.  I believe I mentioned
above that someone years ago used a caulk here, painted black to match the
fossil.  I am wondering what various members of the list-server would
recommend here.  Two ideas we have had were to use a 100% silicone caulk -- 
already colored black.  Another idea was to use an acrylic modeling paste,
painted black after it is dry.  What are the advantages or disadvantages of
the above -- and what alternatives might be suggested?
>
>
>
> Bob Glotzhober
> Curator, Natural History
> Ohio Historical Society bglotzhober at ohiohistory.org
> 1982 Velma Avenue 614/297-2633
> Columbus  Ohio  43211-2497 fax 614/ 2972233
>
>
>
>