Polishing Epotek 301

Robert K. MacDowell <macdowell_r [at] mediasoft__net> writes

>Does anyone have experience with restoring a highly polished and
>"glasslike" finish to Epoxy Technology's Epotek 301 or 301-2 after
>it has been cured and then shaped by mechanical means that take away
>the glossy finish that exists before shaping? ...

It has been awhile but you will need to wet polish this sample to
prevent thermoplastic problems during the process.  Such problems
are usually evidenced by "balling" artifacts

>From your message I am not sure whether you have an infill, a cast
or model, or a thick section specimen holder.  However, in general
the process is similar.

If you can use water as part of your refinishing process then this
will provide the fastest and perhaps the best finish.  If you cannot
use water but can use an oil then you should use a fine grade of
light mineral food grade oil.  Substitutions can be made as required
or mandated by associated materials if this is in a composite
structure.

Instructions below are for water elutriant polishing.

My preference is always for water for this process.  Add a
surfactant such as the old Kodak Photoflo or a simple soap that you
would use for other conservation purposes.  Quantity of surfactant
is small and non-critical.

Use of spritzer bottles of distilled or deionized water are
recommended. One bottle for clean water and another for water with
the surfactant added.

If you cannot move the specimen or model on the abrasive paper then
you must adapt the following process to suit.  Typically you would
do this with strips of abrasive material applied to the artifact.

Additional materials needed include:  piece of plate glass several
inches larger on each dimension than the largest piece of abrasive
paper; supply of wet dry abrasive paper beginning at 320 and
proceeding through 400, 600, 800 and if need be 1000 and 1200.

During the abrasive polishing process the direction of travel must
be such as to create random movements.  Moving back and forth in one
direction will not work.  We typically achieve this by using a lazy
8 movement of the hands holding the specimen.

Lightly spritz clean water onto the glass plate.  Place the first
piece of wet/dry abrasive paper back first onto the wetted surface.
It shouldn't slide around when pressure is placed on it.  Then
spritz the abrasive side of the paper with the water and surfactant.
Place the epoxy artifact/specimen onto this surface and with a light
pressure of the fingers move about in a lazy 8 figure.  Do not move
quickly or let the surfaces dry out.  Inspect the surface being
polished and when the sanding pattern looks uniform, clean off with
clear water, change to the next finer grade of paper and repeat. Pay
particular attention to cleaning off any grit or epoxy debris during
the polishing and particularly prior to using a different grade of
paper.

The better the surface gets the more surface suction will be felt,
go carefully.  The dry surface will be less gloss polished looking
than the wetted surface so you might have trouble determining when
you are finished if you don't dry off the polish surface to inspect
during the latter stages.

This whole process takes longer to describe than to do.  I do not
like machine polishing for this purpose although it has its place
when micropolishing which you may have to do to achieve an extremely
smooth surface.  Micro abrasive containing buffing solutions are now
commonly available.  These can be used for final buffing of the
specimen surface by hand or using your Dremel tool.  Depending upon
your specimen, and your project needs you may or may not be able to
enhance the final clarity of this process with an application of wax
or use the microabrasives in a wax emulsion and simply buff off the
surface leaving a microlayer of wax behind to fill any gloss
stealing surface irregularities.

If you are needing to polish an infill you will have to adapt the
above process keeping the "spirit" behind the techniques rather than
the planar approach outlined.

Mark MacKenzie
M.A.C. (Queen's)
Conservator, Saskatchewan Western Development Museum


                                  ***
                  Conservation DistList Instance 18:8
                 Distributed: Wednesday, July 21, 2004
                        Message Id: cdl-18-8-008
                                  ***