Gary Wagoner on fri 10 aug 07
I haven't experimented with graphite on clay, but want to correct one
repeated but incorrect statement. Several people have said that
graphite, being carbon, would obviously burn off. Graphite is carbon,
but has a particularly stable crystalline structure. It's nothing
like charcoal. Graphite is commonly used for molds for casting molten
glass, so can withstand quite high temperatures. I'm not sure at what
temp it would burn or degrade, but as has been noted, it works as
surface ornamentation at least at low-fire temps.
Gary Wagoner
On Aug 10, 2007, at 3:22 PM, Duff bogen wrote:
> Hank, Karen et al.
> Graphite is a carbon mineral but pencils are not pure carbon.
> Pencils are made with mixtures of graphite and clay and sintered.
> This is how different hardnesses are made. Maybe traces from
> pencils are from impurities in the clay.
>
> Duff
>
> pdp1@EARTHLINK.NET wrote:
> Hi Karen,
>
>
>
>
> Graphite from a regular Pencil kind, being Carbon, would burn off
> with no
> trace.
>
> Physical indent lines of course would remain.
>
>
> Special Pencils which have Oxides or other materials in their marking
> ability, would - by experiment - be found to leave one or another
> color or
> kind of line after fireing.
>
>
> Possibly conventional Color Pencils might be something to try...or,
> there
> are special Pencils made just for drawing on Clay, so that the
> lines of
> definite color will remain after it is fired.
>
>
> I know one may make their own Pencils for this, useing known Oxides
> which
> one blends with some hard Wax, a little Tallow maybe, and whatever
> else, and
> can wrap or roll the central thin 'lead' part between to flat
> thjings to
> make it round and tidy, then roll that in lightly glued Paper for
> making a
> handle for it, for handleing and use...or devise some other means
> of them
> being able to be handled and held...
>
>
> I have never made them, so I only know of a little hear-say or old
> readings
> about them.
>
>
> Good luck...!
>
>
> Phil
> l v
>
>
> ----- Original Message -----
> From: "karen gringhuis"
>
>
>> Can anyone please tell me if line drawing with a
>> regular somewhat soft lead drawing pencil will remain
>> & show up on the ware after bisque firing?
>>
>> Same qn w/ underglaze pencil - drawing w/ soft
>> pressure so as not to incise the greenware?
>>
>> I know underglaze pencil used on bisque ware will show
>> up after C/10 glaze firing & will show thru glaze.
>> What about regular drawing pencil used on bisque?
>>
>> (Why I suddenly started making marks I have NO idea.)
>>
>> TIA!!
>>
>> Karen Gringhuis
>> KG Pottery
>> Box 607 Alfred NY 14802
>
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Ivor and Olive Lewis on sat 11 aug 07
Dear Gary Wagoner,=20
You are correct in stating that Graphite is the stable crystalline form =
of natural carbon. Diamond is unstable and black inclusions of Graphite =
are precipitated within the gemstone. Heated in a vacuum Graphite =
sublimes, the temperature I have for this event is 3700 deg C . Heated =
in Air, Diamonds burn above about 850 deg C
My experience of using 6B Graphite drawing sticks (Toison D'Or =
Progresso) is that above red heat the marks burn away due to oxidation.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
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