Resin and synthetics — Arden Pen Co

“Acrylic” gets used as a catch-all for anything that isn't wood, which is a bit like calling every timber “oak”. Knowing which family a blank actually belongs to tells you how it will look, how it will wear, and why one costs three times another.

The families

Cellulose acetate

The classic pen material, and what most vintage pens are made of. Made from plant cellulose rather than crude oil, it has a depth and a warmth that cast acrylics struggle to match — colours seem to sit inside the material rather than on it. Takes a glorious polish.

Casein & Erinoid

Genuinely strange stuff: a plastic made from milk protein, patented in 1899 and manufactured in Stroud under the Erinoid name for most of the twentieth century. Warm, slightly translucent, with a character somewhere between horn and stone. It's hygroscopic, so it isn't the material for a pen that lives in a bathroom, but nothing else looks like it.

Ebonite & vulcanite

Vulcanised rubber — the material the earliest fountain pens were made from. Warm to the touch in a way no plastic manages, slightly softer under the hand, and it develops a patina with use. Traditionalists will accept nothing else. Black ebonite will fade towards bronze over years in sunlight, which some people consider a fault and others consider the point.

Polyester & Alumilite

The workhorses of modern blank casting. Polyester is hard, glassy and takes an exceptional shine. Alumilite is a polyurethane, slightly more forgiving, and it's what most hybrid wood-and-resin blanks are cast in — timber and colour poured together so the grain runs into the resin.

Cast acrylic

Kirinite, DiamondCast and similar. This is where the pearlescent and metallic effects live — mother-of-pearl shimmer, deep sparkle, colours that shift as the pen turns in the light. Extremely hard-wearing and completely stable. If you want maximum visual drama with no maintenance whatsoever, this is the answer.

Conway Stewart heritage stock

Conway Stewart was founded in 1905 and spent a century as one of the great British pen houses, its pens passing through the hands of writers, statesmen and royalty. When the original company went into liquidation, the remaining blank stock — acrylic, casein and ebonite — was acquired intact.

I hold a quantity of it. It is not a reproduction, a tribute or a colour-match: it is the actual material, cast for pens that were never made. There is a finite amount in the world and no more of it is coming. A pen turned from it is a small act of custodianship, which is a slightly grand way of saying I'd rather it was used than sat in a drawer.

Note: the Conway Stewart name is currently traded by Bespoke British Pens Ltd of Emsworth, Hampshire, who acquired it from receivership in 2014. That is a separate company from the original firm.

Choosing between them

If you want	Ask for
Maximum colour and sparkle	Cast acrylic — DiamondCast or Kirinite
Vintage character	Cellulose acetate, casein or ebonite
Warmth in the hand	Ebonite
Wood and colour together	An Alumilite hybrid blank
Something genuinely finite	Conway Stewart heritage stock
Zero maintenance	Any cast acrylic