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Subject: C-Spray


From: Howard S. Bowen <hsbowen>
Date: Friday, October 11, 1996
Sub-Micron Cleaning Systems respectively requests the opportunity to
use the Conservation DistList to introduce a new cleaning technique
called C-Spray (also known as solid/gas carbon dioxide (CO2) spray
cleaning) to the professionals working in the fields of
conservation, preservation and restoration.  It has been just 10
years since C-Spray cleaning technique was first introduced.  We
have searched the archived information available through
Conservation OnLine and have not found any references to this
method having been investigated for use or a report of an
application where it has been used.  To date we have contacted more
than twenty professionals working in art conservation of which none
had ever heard of this technique before we brought it to their
attention.  Even though the individuals we have spoken with, and
demonstrated to, were not familiar with C-Spray they have all
encouraged us to promote our products and services to the art
conservation community.  We know that C-spray will not remove every
contaminant from every surface; however, the results we have
obtained in other industries demonstrates it has the potential to be
an effective tool in the care and treatment of art objects.

C-Spray has been developed using technology originating in the
aerospace and semi-conductor fabrication industries.  The technique,
in  brief, involves directing a spray at the surface to be cleaned
which contains a mixture of gaseous CO2, serving as the propellant,
and submicron sized bundles of CO2 molecules appearing as solid
particles, which serve as the cleaning mechanism.  The solid CO2
bundles deliver a small but measurable amount of momentum to the
contaminant on the surface, removing it, but with less energy than
that which would scratch, abrade, or signature the surface in any
way.  The cleaning ability of C-Spray at an exit pressure of
20-40 psi is more effective at removing contaminants than a
high-pressure spray of gaseous dry nitrogen (GN2) or clean dry air
(CDA) at 200 psi.

C-Spray has been tested on the most delicate surfaces, including
optical coatings (i.e. gold, silver, aluminum) which are only
angstroms to microns thick themselves; no damage or signaturing of
any kind has been detected using the most precise analytical
equipment.  The delicate nature of the solid bundles of CO2
molecules causes them to fall apart when they impact the surface
being cleaned or the contaminant being removed; thus giving C-Spray
its characteristic of being a non-contact cleaning method.

C-Spray can be used in such a manner that the object being cleaned
is subjected to nothing more than carbon dioxide.  Nothing else
comes in contact with the surface; therefore, water, moisture,
solvents, or other media are not involved in the cleaning process.
C-Spray can be used on paper, cloth, wood, metal, metal alloys,
glass, stone, ceramics, precious metals, and composites.

Even more exciting than the safety offered to the work being cleaned
is the cleaning ability of C-Spray.  While being delicate enough to
be considered a non-contact cleaning method, C-Spray's cleaning
efficiency will remove contaminants such as dried polishing
compounds, waxes, solvent residue, soot, mold, and even
fingerprints.  Another advantage of C-Spray is that it cleans very
quickly.  In tests on many different media, from books to sculptures
to manuscripts to artifacts, C-Spray has removed in seconds what has
traditionally taken hours, even days, and all without making
physical contact to the surface.

Lastly, C-Spray does not leave behind any residue or waste other
than the contaminant removed from the surface.  The solid CO2
bundles sublime to become CO2 gas which is removed via the air
exchange system.  Because C-Spray does not generate CO2, it makes
use of CO2 collected as a by-product from many industrial processes,
it has been approved by the EPA as an environmentally compatible
cleaning process.

In order to be complete in our delivery of information we will
mention some conditions that co-exist when using C-Spray.  First,
the temperature of the solid bundles of CO2 molecules in the spray
stream is -70 degrees Centigrade (-110 Fahrenheit).  The temperature
of the surface at which the spray is directed can drop as rapidly as
60 degrees per second; however, because the cleaning typically
occurs with less than 1/20th of a second exposure to the spray, the
temperature of the surface will only drop a few degrees.  Under
these circumstances the temperature drop would be similar to that if
acetone was applied to a surface and allowed to evaporate.  Second,
C-Spray will not reverse chemical reactions, it is best suited for
removing surface contaminants such as dirt, or contaminants adhered
to the surface.  Changes to the surface such as stains, fading,
molecular discoloration, natural occurring patinas will not be
effected by the spray.  Third, carbon dioxide is heavier than air
and must only be used in areas with adequate air exchange.

We believe this to be an exciting new cleaning technique with a
great potential in the community of fine art conservation.  It will
enable many cleaning tasks to be accomplished in a fraction of the
time required by traditional methods, cleans more thoroughly in many
cases, and makes possible some cleaning tasks that have previously
been cost prohibitive or impossible.  In the near future Sub-Micron
will introduce an even more efficient system called C-Strip which
will have the ability to remove even more difficult contaminants
such as corrosion, rust and paint.  Just a few of the possible
applications that have been brought to our attention are:

    *   Disaster recovery including soot removal after a fire could
        happen in a fraction of the time than current methods

    *   Surface dirt could be removed from paper surfaces without
        removing any of the base material that occurs when even the
        softest erasers are used.

    *   Deposits of mold or fungus could be driven off the surface
        directly into a filter for disposal without making physical

    *   Vast quantities of contaminated material could be cleaned
        without generating any residue other than that removed from
        the surface which would have to be dealt with anyway.

    *   Cleaning devices could be installed at the end of a fiber
        optic probe that would clean deep inside a remote cavity,
        and also clean the end of the probe tip if it became
        contaminated during the cleaning process.

    *   It could become an additional tool in the cleaning and
        restoration of outdoor and indoor sculpture.

After seven years of experience providing C-Spray cleaning equipment
to the optics and semiconductor industries, Sub-Micron is attempting
to introduce this technique to the art community.  Sub-Micron will
only provide its products and services to the art community through
qualified and recognized professionals, but only under our
supervision.  We feel this is necessary to ensure that the
technology is not misused or misunderstood.

Sub-Micron hopes that this introduction would serve as the impetus
for a review by the professionals working in the areas of
conservation, preservation and restoration.  We are happy to respond
to comments, questions, concerns, criticisms, etc., as they appear on
Conservation DistList.  We are interested in working with anyone who
would like to investigate C-Spray or who may have an application
that would benefit from C-Spray's capabilities and be willing to
report the results via Conservation DistList.  We are willing to
respond to any requests for more information, a demonstration of the
C-Spray cleaning technique, or a full discussion of its capabilities
and applications.

Thank you for your consideration,

Howard S. Bowen, President
Sub-Micron Cleaning Systems
Post Office Box 219
Carpinteria, California 93013-0219
United States of America
Telephone: 1-805-566-3830
Fax: 1-805-566-3813

                  Conservation DistList Instance 10:36
                Distributed: Saturday, October 12, 1996
                       Message Id: cdl-10-36-002
Received on Friday, 11 October, 1996

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