Alwan Isograph Technical Pen, 0.4 mm Nib

A technical pen draws a line of exactly one width, in any direction, with no variation from pressure or angle — which is the entire point of it. The nib is a fine steel tube with a weighted wire inside that keeps the channel clear, and the pen refills from a bottle instead of being thrown away when it runs dry.

Technical pens are for drawing that has to be measured rather than felt: architectural work, plans, orthographic projection, ink hatching, and stencil lettering. Hold it close to vertical — a tubular nib laid over at an angle starves and skips. And the single habit that decides how long the pen lasts is capping it the moment you stop: ink drying inside the tube is what blocks a technical pen, and clearing a blocked nib is slow, fiddly work.

0.4 mm is the standard writing and labelling weight, and the size most people buy first.

• Tubular steel nib — one constant line width in every direction
• Refillable from a bottle of technical drawing ink
• Hold near vertical; a tilted nib starves and skips
• Cap it the moment you stop — dried ink inside the tube is what blocks it