Molten polymer is blown through fine nozzles into fibers that have a core of one plastic and a sheath of polyester around it. Its sheath softens at a lower temperature than the core.

Gathered into a rod and heated, the fibers fuse wherever their sheaths cross. The result is a long rod full of tiny connected channels, which is cut to length for ink reservoirs and tips.

Short pieces of the denser rod are cut or ground to a bullet point or a chisel edge. Older permanent markers used polyester felt hardened with phenolic resin instead.

Barrels, plugs and caps are injection molded from plastic. A snug cap keeps the solvent from evaporating out through the tip.

Dye or pigment is dissolved in an alcohol-based solvent with a resin for grip. Permanent ink once relied on toluene and xylene, and most markers now use milder alcohols, while dry-erase ink adds a release agent so it wipes off glass and enamel.

Workers push the fiber rod into the barrel and inject a measured dose of ink that soaks through it. Last, the tip is pressed into the open end so it touches the soaked rod.

The back plug and cap go on, and samples are drawn across paper to check ink flow and line width. In one industry test, a marker stored tip up for 48 hours must write by its third stroke.