What Are Pens and Brushes

A pen is a writing instrument which applies ink to some surface.

Terms and Expressions
Originally the word meant quill, and is derived from pinna, which is Latin for feather. This is because early pens were made from goose feathers by carving the feather with a penknife. Pen is also used as a verbal expression of "to create" or "to write"; for example, "Today, I think I'll pen the Great Canadian Novel." Pens may also be known, although not very commonly, as frindles. This word was invented by the author Andrew Clements in his novel Frindle, the premise of which is that a schoolboy decides to call pens "frindles" and the usage becomes common throughout America.

Types
Types of pens currently in use include the ballpoint pen, the fine-line marker pen, the artist's pen, and the fountain pen.

A ballpoint pen is a writing instrument, more specifically a pen, similar to a pencil in size and shape. There are two basic types of ball point pen: disposable and refillable. The ball point pen was invented in 1938 by the Hungarian journalist Laszlo Biro.

An erasable pen is a kind of pen whose ink can be erased. It is usually a ballpoint pen. Gel pens are sometimes erasable as well.

The term brush refers to a variety of devices with bristles, used for cleaning, grooming hair or painting. See below for other, less common meanings.

Paint Brushes
Paint brushes are used for applying ink or paint. These are usually made by clamping the bristles to a handle with a ferrule.

Paint brush can also refer to the digital equivalent one would find in a bitmap graphics editor, i.e. a virtual brush that can modify a digital picture.

Paint brushes can have three shapes:
Round: The long, closely arranged bristles of these brushes enable them to hold more paint than other similarly sized but differently shaped brushes. This is why many artists prefer them for painting large areas and for color washes.
Flat: These spread paint well
Fan-shaped: These mix paint well.

Brush Care
Paint must be cleaned from brushes immediately after use. This is especially true for oil and acrylic paint because removing dry, set residue can take bristles off or ruin a brush's shape.
Never leave brushes bristle-end down in a container of water, turpentine, or any other solvent (if you want to clean them, do it by hand or with a wet cloth). This is because the bristles of the brush spread out against the bottom of the container and, will, if left too long, set that way (like hair).

Decorators' Brushes
The sizes of brushes used for painting and decorating, usually given in mm or inches, refer to the width of the head.

Common sizes are:
1/8  inch, 1/4  inch, 3/8  inch, 1/2  inch, 5/8  inch, 3/4  inch, 7/8  inch, 1 inch, 1-1/4 inch, 1-1/2 inch, 2 inch, 2-1/2 inch, 3 inch, 3-1/2 inch, 4 inch.
10 mm, 20 mm, 30 mm, 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, 100 mm.
Bristles may be natural or synthetic. Handles may be wood or plastic; ferrules are metal (usually nickel-plated steel).

Artists' Brushes
Artists' brushes are usually given numbered sizes, although there is no exact standard for their physical dimensions.

From smallest to largest, the sizes are:
7/0 (also written 0000000), 6/0, 5/0, 4/0, 000, 00, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 16, 18, 20, 22, 24, 25, 26, 28, 30. Sizes 000 to 20 are most common.

Bristles may be natural - either soft hair or hog bristle - or synthetic.
Soft hair brushes are made from Kolinsky sable or ox hair (sabeline); or more rarely, squirrel, pony, goat, or badger. Cheaper hair is sometimes called camel hair... but doesn't come from camels.
Hog bristle is stiffer and stronger than soft hair. It may be bleached or unbleached.
Synthetic bristles are made of special multi-diameter extruded nylon filament.

Artists' brush handles are commonly wooden, but the cheapest brushes may have molded plastic handles. Many mass-produced handles are made of unfinished raw wood; better quality handles are of seasoned hardwood. The wood is sealed and lacquered to give the handle a high-gloss, waterproof finish that reduces soiling and swelling.

Metal ferrules may be of aluminum, nickel, copper, or nickel-plated steel. Quill ferrules are also found: these give a different "feel" to the brush.