Technical pen

From Wikipedia, the free encyclopedia

A technical pen is a specialized instrument used by an engineer or draftsperson (British: draughtsperson) to make lines of constant width for architectural, engineering or technical drawings. It has been also generally called "rapidograph", albeit this particular name has officially remained a proper name for a line of products made by German company Rotring.

1 History
2 Related Technologies
3 References
4 External links

[edit] History

Early technical pens consisted of a small pair of calipers, having one flat and one bowed leg holding ink between them. By adjusting the gap between the legs the width of the line drawn by the pen could be adjusted. Such pens, kept at a constant angle to the paper, were used for ruling lines, but not for cursive handwriting, nor for off-hand flourishes. The Graphos technical pen introduced in 1934 miniaturised the caliper principle and made the points easily interchangeable.The Sheaffer company produced an expensive draughting set which included such pens for use on linen prints. These sets were often presented to a draughtsman upon becoming 'time served', which is marking the end of the apprenticeship.

In the 1950s, fountain pens with cylindrical points became available, but they were complex instruments with tubes holding a tiny shaft. To release ink the shaft is depressed and a line of about the width of the exterior diameter of the tube can be drawn. Additionally, in later models, the tube had a small ledge that effectively narrowed its end, that - while maintaining the line thickness - made the tube thicker along most of its length and also protected ink from spilling while drawing along the edge of a rule, set-square, T-Square or other template (the ink had no immediate contact with the template's edge). Some special, more expensive nibs were equipped with tubes made of tungsten or with their tips made of synthetic precious stones, to slow their wear on hard surfaces.

In the 1960s, the pen's design evolved to feature tubes of ink that were filled with an eyedropper or from a narrow spout on a special bottle of ink. Such pens frequently came in sets of various sizes, and several pen points which were installed into the holders that also contained a filled fountain, which in turn would be screwed into a handle. The construction and amount of parts varied depending on the company, and the parts were not cross-compatible in most cases. Some later designs (like the Staedtler MarsMatic700) had especially designed channels to allow better air flow in between the wall of the external grip and the point assembly. This made ink flow more reliable. The general drawback of this group of pens is that they have to be frequently and carefully cleaned to remove all ink from the tubing, otherwise it would set and could not be removed.

In the United States, several firms produced this kind of technical pen: WRICO, Leroy, and Koh-I-Noor. Each had its own proprietary sequence of line widths, meaning that the widths were not standardized across the industry, and each company's specifications for the widths did not match the others. And the specifications were given as fractions of an inch, not in the metric system. In the case of rapidographs made for the US market, they were both marked with symbolic (4x0, 3x0, 2x0, 0, 1, 2 etc.) and metric values.

For the rest of the world, the most recognised brands were Staedtler, Rotring and Faber-Castell; currently only Staedtler still makes the traditional technical pen. A full set of pens would have the following nib sizes: 0.13, 0.18, 0.25, 0.35, 0.5, 0.7, 1.0, 1.5, and 2.0. However, the International Standards Organization/Organisation (which replaced the Metric System) called for 4 pen widths: 0.25 (white), 0.35 (yellow), 0.5 (brown), 0.7 (blue); these nibs produced lines that related to the text character height and the ISO A-series for paper.

The A-series for paper starts with ISO A0, which is one square metre in area with the sides in the ratio or proportion of 1 to the square root of two... which is 1189mm by 841mm. If this paper sheet is folded in half, the ratio of the sides remains constant, and the sheet is now ISO A1, measuring 841mm by 594mm, folded in half again, gives ISO A2 and so forth.

A text character (produced by an ISO stencil template for use with the technical pens) of 5mm in height, would have a stroke or line thickness of 0.5mm, and so would require a brown nibbed 0.5 pen. If this character used on an ISO A0 sheet and reduced in reproduction to half it's original size (ISO A1), the character is now rendered as being 3.5mm high with a stroke thickness of 0.35mm -- so changes could easily be made to reductions or enlargements as everything is in proportion. This worldwide (except for the USA) standard ensured that drawings could always be legible even after microfilming, photocopying and faxing.

The main draughting sets of four nibs came in two kinds: Gold and Silver. The Silver was for rough tracing paper, and the Gold was for plastic film (velograph or durables). Drawing boards changed as a result of technical pens -- a hard (not spongy) surface was required, and when plastic film was used, the static attraction between plastic cursors, T-Squares, Set-Squares etc. means that as you lifted the edge from the film, the film would rise through static attraction and the ink would blot. The solution was to stick down a plastic sheet (Osalid) that attracted the film better than the draughting instruments. The tracing paper or velograph sheet would be placed on the Osalid sheet stuck onto the drawing board and the air brushed away. Brushing charges the surface, and the film would then be taped taught (but released at the end of each working day to allow for overnight temperature expansions and contractions).

When pen plotters became widespread as large format computer output for engineering purposes, special variety of point assemblies were produced. They had the same basic characteristics of the standard pen nib, but the tube was much thicker in order to strengthen it against the constant and fast side movements. Only the tip of the tube had the desired, line-size width. They were discontinued when the era of widespread pen plotters' use was over.

While the rapidograph style of pen is still widely used by artists, the use of computer-aided design (CAD) has replaced the need for manual drafting/ draughting, and developments in the field of felt-tip, pigment ink-based pens, made the technical pen a cheaper, low-maintenance and disposable tool. In general, the development of technical pens has evolved through a gradual sacrifice of line and ink quality in favour of ease of maintenance and use.

[edit] Related Technologies

Drawingboard instruments, such as set squares, shape templates, text stencils and french curves are used to make consistent marks on the paper. A technical pen can be attached to a pair of compasses to produce circles.