What is the best pen to draw ?

Many times my students, drawing novice restless, I have been asked what should be the best pen to draw and always tell them that the question should not be-what is the best pencil drawing ?, What -but rather ES pencil I use for this or that purpose drawing ?.
Now, as he wished them the best answer I happened to do with the example of an eye I was drawing with each use pencils. This seemed like a very appropriate way to explain the advantages and disadvantages of each pencil. Thus, seeing the results, they could choose the one that suited them for his purpose. Ok?, notes.
The bar told thick soft.

Advantages: For the physical qualities of this bar you can achieve similar effects to those made with the technique of pastel (only in black and white) and strokes can be very dynamic and expressive (very "loose" and spontaneous); characteristics that give much artistic character to the work. The blacks who succeed are "absolute", ie, powerful and dense, but can also be achieved very broad ranges of gray with mechanical pencil (graphite pencils do not allow any of these possibilities).

Disadvantages: It's difficult to control because it tends to soil or stain job. You can not make very detailed work and does not let you delete or correct almost.

Recommendations for use: This amazing bar you will find excellent for quick, loose sketches; to experiment and search for previous effects to a final work with another technique to color. For the drawing of first intention. It is ideal for general studies of light and shadow.

Recommended Type of work: Definitely for the naked human figure or sketches of landscapes.

* Tip: When working with it ensures that the picture is as large as possible (60 cm x 90 cm, ideal), a reduced size limits you and in the case of exercise, preferably I work it on economic papers, you must place with clamps (Bulldog) in a table. Always place the table in a vertical or nearly vertical position.