Fill materials for stone

John Griswold <griswold [at] silcom__com> writes

>I am writing the section on structural fills for stone in the
>upcoming JAIC special edition on loss compensation, and would
>appreciate any input on this or related subjects for possible
>inclusion in the overview.  I would like to find out how individual
>conservators have developed their own recipes for making translucent
>fills with fumed silica-bulked epoxy, etc.

I have been using the colloidal form of silicon dioxide, or fumed
silica to modify fluid systems to create a wide variety of
adhesives, fillers, and poultices for over twenty years.  I continue
to experiment with the colloidal form of silicon dioxide "fumed
silica", however it is the colloidal form of titanium dioxide and
aluminum dioxide which are most useful in creating translucent fills
for porcelain, marble, gemstones, and in replicating many glazes.
Made by the same condensation process as fumed silica, the
astonishingly small particle size of fumed titanium dioxide imparts
the desirable translucent depth which is difficult to achieve with
fumed silica alone. Titanium Dioxide P25 (also referred to as
Titandioxid P25) and Aluminum Oxide C are available (last I checked)
from:

    Degussa Corporation
    Pigment group
    Sample and literature Dept.
    150 Springside Dr.
    Akron, OH 44333
    216-668-2235

I suspect the day will come when samples will be difficult to get
and one of the conservation supply companies will hopefully pick
these products up.

Try using it in combination with fumed silica and whatever pigments
seem appropriate for your fill. For marble, precipitated chalk
always seems to find its way into the mix.

Bye the way, if you are using Hxtal as your medium, many
conservators have recently been experiencing difficulty with Hxtal
because of  yellowing observed during cure. Yellowing does not seem
to progress once the cure reaction is complete, however it does seem
to  increase if the temperature is elevated to as low as 85 degrees
F. It may be a hit or miss situation depending upon the batch.  If
you continue to use this epoxy, I would suggest testing each new
batch to determine if the product still meets your requirements.

Greg Byrne
304-535-6140

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                  Conservation DistList Instance 10:23
                  Distributed: Friday, August 30, 1996
                       Message Id: cdl-10-23-005
                                  ***