What’s in a pencil lead?


Pencil refills waiting to be obliterated in a fiery maelstrom.

“Dear Pilot Pen Company Ltd please tell me what you put in your pencil leads”

To Whom it May Concern,

I am a scientific researcher in the Department of Physics at Imperial College, London. I work on the MAGPIE facility, which uses huge electrical currents to convert solid materials into plasma, a form of hot, electrically charged gas.

I’ve recently began to study plasmas made from carbon, and as a source of solid carbon I’ve turned to mechanical pencil refills, specifically the Pilot Eno 2B, 0.3mm diameter. I know from some reading on the internet that mechanical pencil refills are a mixture of graphite and a strong polymer that is added to stop the graphite from breaking under mechanical stress.

I was wondering if you could help me identify the chemical formula for the polymer used in the Pilot Eno 2B 0.3mm, and what fraction of the pencil refill is polymer, and what fraction is graphite. This is important for me to fully understand the experiments we are doing – if a large proportion of the pencil refill is not carbon, but say hydrogen or oxygen, my results will be quite different.

I appreciate this request is unorthodox, and the precise details may be commercially sensitive. If you could offer any assistance with my query I would be very grateful.

Kind Regards,
Jack Hare

Post-Graduate Researcher,
Imperial College London

“The people who know stuff are in Japan and we don’t talk to them.”

Dear Mr Hare,

Thank you for your enquiry which has been passed to me.  Unfortunately I do not have information beyond the basic marketing copy which is available on our website.  Our technical department in Japan does not release information on chemical formula used in the manufacturer of our product so regrettably I am unable to provide an answer to your question.

Sorry that I cannot be of more help.

Kind regards,

Stuart Barker

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