# Common ink cap (Coprinopsis atramentaria)

**Coprinopsis atramentaria**

**Known today as.** A grey mushroom that dissolves into black ink as it ages.

Kind: Fungus  
Poisoning: Coprine and alcohol (https://thethinkingpress.org/materia-medica/poisons/coprine)  
Toxic: yes

> **Caution.** Poisonous with alcohol, even days later.

## What was it used for?

Its black liquid was once used as ink.

## What does modern science say?

Its coprine blocks the breakdown of alcohol, as the drug disulfiram does, so that a drink taken days after eating it brings flushing, nausea, and a racing heart.

## Pharmacognosy and toxicology

- **coprine**: 

**Mechanism.** Coprine’s metabolite blocks aldehyde dehydrogenase, so alcohol builds up as acetaldehyde.

**Dose.** Any amount, with alcohol, within about three days.

**Standing.** Edible without alcohol.

## What lore surrounds it?

“Tippler’s bane”: harmless on its own, it turns cruel with wine.

## Sources

- Wikipedia, “Coprinopsis atramentaria,” en.wikipedia.org (read 2 October 2026).
- Wikipedia, “Coprine,” en.wikipedia.org (read 2 October 2026).

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*Common ink cap.* In *Materia Medica*, edited by B. C. P. Statema. Version 1, revised 2026-10-03. The Thinking Press. https://thethinkingpress.org/materia-medica/common-ink-cap

Historical description, not medical advice.