Larry Mayo asks about a solvent for silicone adhesive.  Once it is
cured, I don't know of anything pleasant that will dissolve it.  You
can call the company (GE - DOW - etc.) and get some information.

But I hope you are asking about making it less viscous, i.e., more
runny.  The answer is to add some naphtha.  You can go out and buy some
lighter fluid for $3 an ounce or you can just buy a quart for $2.50 at
the hardware store.

You may also know that there are a lot of different types and colors
of silicone sealant.  I have found the black stuff particularly handy.
In fact, you can buy a tube that is already 'thin'.

There are also 3 types of sealant.  The familiar one has a vinegar
smell and cures with acetic acid.  There is another that is alcohol
based instead.  It is used to 'pot' electrical parts because the acid
would cause a problem.

I bought some of the alcohol based silicone to use for the same reason
and I expected to be able to thin it with alcohol.  Big surprise.
Water won't work either.  Back to the naphtha an both cases.

Another thing you should know: if you mix the naphtha at 50% by volume,
it will harden pretty much as normal.  However, after a few days a
1"x1"x1" cube will become a 3/4" cube.

Regards,
Craig Smith