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Preliminary sketches
Every scientific illustration begins with a rough sketch - usually several sketches. Many details must be discussed between the artist and scientist before a final drawing can be done, and several additional preliminary drawings must be prepared in order to work out aesthetic details, such as shading and other aspects. The Kellogg Illustration Collection provides many examples of this process. (See Pantograph section for more details about how Prentice prepared his preliminary drawings.)

manus manus pen and ink
skull sketch skull pen and ink
Parietobalaena sketch Parietobalaena
porpoise skeleton

The pen and ink thick/thin line technique

Pen and ink line illustrations are clean, crisp, clear, and inexpensive to reproduce, making them ideal for scientific illustrations. Sydney Prentice was a master of the pen and ink thick/thin (eyelash) technique. This is a very difficult but beautiful technique, and is especially well-suited for drawing vertebrate specimens because of the grain inherent in bone. 

To execute the thick/thin line technique, an artist must use a dip pen with a flexible nib loaded with ink. Then, a single line is made which can vary from thick to thin depending on the amount of pressure placed on the pen while drawing the line. With this technique, it is possible to create a complex system of lines to denote form, structure, texture, light and shade using a very high contrast black/white medium. No gray is present; only the impression of gray created by line.

Ink drawings are made on a heavy drawing paper, such as Bristol Board.

Now, an artist could do the same technique with a computer and proper software, drawing tablet, or monitor.

enlargement of thick thin line example line example close up

We showed the illustrations to Alice Tangerini, scientific illustrator in the Department of Botany (NMNH), whose specialty is pen and ink line illustrations of botanical specimens. Alice studied the line quality of the Prentice illustrations and determined that he probably used a flexible Joseph Gillott 291 pen nib and holder to do the illustrations. Many of his lines are long, and vary from very thin to thick. This requires using a nib long enough to be flexible and large enough to hold enough ink to render the length of the needed line. Prentice‚Äôs lines are far longer than those any crow-quill pen, even with an appropriately sized nib, would be able to produce.

pen and ink supplies
Julia drawing reducing lens

Pen and ink technique (left); reducing lens used to check drawing prior to publication (right).

Drawing for publication

There is a phrase, coined by past president of the Guild of Natural Science Illustrators, Candy Feller, that says: "Scientific illustrators do it for reproduction." In other words, whereas a fine artist usually plans their images to be best seen in their original form, usually hanging on a wall, scientific illustrators plan their illustrations so that they look their best in when published. This is a unique way to approach a drawing and requires experience to do it well. In this regard, Sydney Prentice was also a master.

Prentice generally drew his illustrations much larger than the final printed piece would be - at times more than twice the size of the published illustration. This allowed him to fit in the many diagnostic details needed in the drawing and it also improved the drawings dramatically in an aesthetic sense. The lines became very, very fine in publication and any small mistakes in line quality would be greatly minimized. This was standard practice for preparing scientific illustrations prior to the advent of the computer.

Prentice would have used a reducing lens, seen above, to check how his drawings would look in publication.

For more information about scientific illustration see the Illustration Techniques section of the Paleo Art bibliography.