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Consolidants and glues



Hello All,

We've been discussing the pros and cons of various "glues" and since I
started this thread I thought it time to add my thoughts and observations.

Since we deal with Late Cretaceous fossils from the Hell Creek almost
exclusively, we encounter a variety of preservational states. Some of our
fossils are rigid on the outside and spongy to absent on the inside. Some
are almost totally replaced by siderite or limonite, with just a thin layer
of the exterior remaining. Some of the fossils are nearly the same chemical
composition as in life, with a light absorption of ground water born
minerals. Some are preserved so well almost no prep work is required, while
others are in need of an ICU.

When we start prep work there has to be a judgment call on what to do with
the specimen. In the field, where the correct use of consolidants is
critical, we encounter our biggest challenge. Without some consolidants on
some specimens they will not even survive the jacketing process. This is
where it gets tricky. In the summer months the humidity and temperature
swings radically from morning to mid-day to late afternoon here in South
Dakota. We use butvar and we have had trouble keeping the mixture(s) at the
same viscosity during the course of the day. We've tried shading the
bottles, keeping them in an ice chest, and other methods with mixed
results. In the morning, when humidity is at its highest, the butvar tends
to cloud, or trap moisture in the curing process. This is totally
unacceptable as it makes for a mess in the lab when the jacket is
eventually opened (all of the butvar must be removed). In the mid-day heat
the butvar tends to cure so quickly it doesn't seem to penetrate the
micofractures and forms a "skin" that only barely holds the specimen
together. In the late afternoon the butvar takes forever to cure and in
some cases we've had to let a specimen wait until the following day to
complete the extraction. The later has its own risks in that most of the
places we collect have cattle roaming around, aching to stomp specimens,
and thunderstorms lurk over the western horizon almost every afternoon.
Have you ever tried to dig a fossil out of sloppy wet bentonite or
mudstone?

So, even though we have settled on butvar, for the very reasons that others
have mentioned, there are problems and drawbacks for its use as a field
consolidant. However in the lab there is nothing better for MOST adhesive
jobs. I have reconstructed Explosaur specimens using nothing else. It works
great for tiny projects, such as an Ankylosaur tooth I just finished
rebuilding, viewable on the GRM website. I have also put tiny theropod
teeth back together, found in bits, using butvar alone. I reconstructed a
huge Edmontosaur scapula late in December, very badly fractured and
compressed, using only butvar. If the specimen can be stabilized during the
curing process, and I mean absolutely still, butvar works like a dream.
I've applied it to the spongy interior, in very thin mixes, with very
little damage to the bone. The trick is to use the LEAST amount required to
get the job done, and use the "right" viscosity for the situation at hand.
How to know the "right" mixture? In our case it's been trial and error. As
has been said, keep good notes, and repeat the processes as closely as
possible.

Now, I must say we have used cynoacrylates in some situations. One example
is the repairing and reconstruction of larger turtles. These beast don't
seem to suit themselves to extended butvar curing times, and the compound
curves makes bracing off to prevent movement difficult at best. We use
these rapid adhesives as sparingly as possible, and only in rare
circumstances.

One other factor is a percentage of specimens with pyrite content. While we
have not expanded to making casts of specimens yet, this may be the only
way to preserve these pyrite infested specimens. We have heard of no
breakthroughs in prevention of pyrite disease short of casting the
original. Does anyone know if a coat of butvar or any other substance will
prevent pyrite from eventual destruction of a specimen?

The bottom line is we have settled on butvar as our main consolidant.
Roger A. Stephenson
Assistant Director
Grand River Museum
Lemon, South Dakota
http://www.grandrivermuseum.org/
http://www.iw.net/~roger/
"Put the bunny, back in the box!"