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Subject: CarbOthello pastel pencils

CarbOthello pastel pencils

From: Michael Skalka <m-skalka<-a>
Date: Monday, April 14, 2008
Magdalena Grenda <turbomi.grenda.magdita.pff [at] gmail__com> writes

>I would like to carry out a research on pigments light fastness and
>durability of CarbOthello pastel pencils. Before I start I would
>like to ask if you know if anybody has already carried out this kind
>of research so I would be able to compare the results or focus on
>other aspects of work with Carbothello, not to duplicate somebody's

The American Society for Testing and Materials (ASTM), D01.57, a
subcommittee of the larger paint and related coatings section of the
society has been working for several years on developing a standard
for artists' pastels.  Much of the preliminary testing to see if a
workable lightfastness test method has been completed.  Data is
being reviewed and correlated to assure the members of the
subcommittee that the lightfastness test methods proposed are
reliable.  The CarbOthello pastels in pencil form have not been
subjected to preliminary testing by the ASTM subcommittee D01.57.
However, if you wish to proceed with your own testing, for all
practical purposes, I believe that the test for pastels will be
similar in may ways to a standard that was recently adopted to test
colored pencils.

The ASTM standard  D6901-06 Standard Specification for Artists'
Colored Pencils provides all of the technical specifications
necessary to properly test the lightfastness of colored pencils. The
adoption of this standard has spurred manufacturers to deploy
pencils sets that are equivalent to the rigorous lightfastness
standards adopted by those making artists' oil paints.  It is a very
stringent test for lightfastness.  Subjecting colored pencils to
1260 MJ/m2 provides sufficient data to allow colorants to be divided
into the 5 lightfastness categories that are part of many ASTM
standards for assessing the permanence of colors.

I would encourage you to visit the ASTM website at
<URL:> and purchase the standard D6901 for your
review and use it to guide you in creating a testing protocol for
your samples.  At this point, it is the closest set of instructions
to date that provides a protocol for lightfastness testing for
products of this type.   ASTM supports it's efforts through
membership and the sale of standards to the manufacturing industry
so the standard must be purchased at a modest cost of $36.00 USD.
I hope this is helpful,

Michael Skalka
Conservation Administrator
National Gallery of Art
Washington, DC
Chair:  ASTM D01.57 Artists' Materials

                  Conservation DistList Instance 21:56
                  Distributed: Friday, April 18, 2008
                       Message Id: cdl-21-56-002
Received on Monday, 14 April, 2008

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