My experience in the use of these products varies dependant on what I wanted
to accomplish...

Silicon----
Silicon is good as an good encapsulator (sealing moisture into a shell), and
can bring out the color of a shell much like oil as it penetrates through
the lattice structure of a shell. However, it is not hydroscopic (does not
attract H2O or bond to), it is rather hydrophobic and non-lipophilic. It is
non-reactive to salts and has a neutral pH, so it cannot facilitate the
breakdown of shells.  It is the antithetical element to Carbon, and is
difficult to emulsify.

Despite using it 20 years ago, I am leery of its use on a shell. The
emulsifiers and solvents used in Armor-All will eventually break-down you
dashboard and items they are used on.  As it penetrates into a shell, I
wonder what effect it will have over time on the organic compounds that
makeup much of the color in shells?

Therefore silicon is best used in a somewhat pure state, whereas the
emulsifiers for silicates may have unintended consequences on our shells.

Mineral Oils----
Historically, hydro-carbon based baby oil and pure mineral oil, which are
composed mainly of alkanes and paraffins (waxes) are a good and expensive
overall choice for protraction our shells and bringing out the color.  Baby
oil has a lower viscosity than typical mineral oil and is missing some of
the raw properties that mineral oil has (although I have not explored what
they are).

Glycerin----
However, when desiring to preserve tissues such as periostracum, esters with
the strongest hydroscopic properties are best, which for our use are
glycerol and ethanol. Ethanol evaporates away, but the two can be mixed
making a thinner emulsion, leaving on the glycerol after evaporation. You
can soak the entire shell in the mixture and the glycerin will be retained
deep into the shell.  Isopropanol does not seem to make as good of an
emulsifier for this and has an undesirable pH level, so a buffer would need
to be added if used.  Ethylene glycol seems only to work as a fixing agent
to preservative a shell with the animal intact, and stored submersed in the
medium.

Hope these thoughts are helpful,
Cheers,
Leslie

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