V. la spiegazione sotto, i gessetti vengono anche oleati per renderli più compatti.
V. anche la referenza

Crayon: Made in the form of sticks, crayons are composed of colored pigments combined with oily, fatty, or waxy binding media. The type and proportion of the binder within the overall mixture determines the consistency, hardness, texture and tenacity of the crayon. In the seventeenth and eighteenth centuries, the term was used to describe fabricated chalks made by mixing ground natural black or red chalk with some form of filler and binder, as well as charcoal that had been modified into drawing sticks by soaking them in oils and soaps. Because the binder is always greasy or oily, the stroke of a piece of fabricated chalk or other crayon is usually more homogeneous and intense than that of the drier and more friable mark left by natural chalk. Today crayon has become a generic term to describe any color stick made with an oily or greasy binder, such as lithographic or children's wax crayons. (Henri de Toulouse-Lautrec, Circus Rider, 1943.923)

ciao Floriana, facendo una ricerca veloce, trovi numerosi hits, ma non sono sicura che sia quello che intendi tu...

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Note added at 16 ore (2007-06-13 08:20:48 GMT)
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naturalmente *pastello grasso nero*

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Note added at 16 ore (2007-06-13 08:22:19 GMT)
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Autoritratto con rana, pastello grasso, cm. 50x60
http://www.stefanovalente.com/A.P.VALENTE-donazione.htm

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Note added at 16 ore (2007-06-13 08:23:49 GMT)
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Le tecniche sono molteplici, conformemente alle diverse fasi e all'universo schizofrenico del protagonista : pennello, pastello beige, linea fragile e spezzata.

Più tardi Fuochi sarà invece l'affermazione del colore e dell'uso del pastello grasso. I colori ritmano la storia e non si limitano ad esprimere, raccontano, dualità che é marca nell'opera di Mattotti.
http://www.ubcfumetti.com/special/0401d.htm

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Note added at 16 ore (2007-06-13 08:27:05 GMT)
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Georges Seurat (1859-91) utilizzò i pastelli per dipingere secondo la tecnica del puntinismo. Nella sua gouache Caffè concerto si servì di pastelli neri per ottenere effetti di densità e ombra. Pierre Auguste Renoir (1841-1919) disegnò con pastelli grassi rossi e neri e più tardi con sanguigna, rischiarando con lumeggiature bianche e accentuando determinati effetti con tocchi neri. Nei suoi pastelli Ragazza con rosa e Lavandaia con bambino sono ben evidenti la qualità delle variazioni tonali, e la leggerezza di linee e tratteggi che creano la lievità delle figure.
http://www.disegnamo.it/articoli/index1.php?id=1051

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Note added at 16 ore (2007-06-13 08:30:54 GMT)
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Qui trovo la definizione di Pastel:
PASTEL Made by blending dry, powdered pigments with a non-greasy, water-soluble binding medium, traditionally a plain gum. The resulting paste is then usually rolled into a stick and dried. Pastels were first used at the end of the 1400s, but they became especially popular in the 1700s and have their own tradition as a medium. A wide spectrum of colors is possible with pastel, and they were often collected and displayed more like paintings than drawings. In the 1800s, pastels were commercially manufactured much as they are today. The term "colored chalk" is often used interchangeably with pastel.
http://www.clevelandart.org/exhibcef/butkin/html/3804852.htm...

e di Black chalk:
BLACK CHALK A naturally occurring composite of carbon and clay that can be cut and sawed into a stick and sharpened to a point for use as a drawing instrument.
http://www.clevelandart.org/exhibcef/butkin/html/3804852.htm...