Washery

A colliery's coal-washing and preparation plant, where run-of-mine coal was cleaned of stone and dirt, crushed and graded by size before sale.

Historical usage

Coal preparation plants -- almost always called washeries in British coalfield usage -- became increasingly important through the 20th century as seams grew dirtier and customers demanded a more consistent, higher-quality product; large purpose-built washeries were added to many established collieries in the interwar and post-nationalisation periods, often as one of the largest and most visible surface structures on the site.

How it worked

Coal washing relies on the difference in density between coal and the stone and shale mixed in with it as it comes out of the ground. Run-of-mine coal was first screened to sort it by size, then washed in water-based separation equipment -- washboxes and, later, froth flotation for the smallest grades -- that let the lighter coal float free of the denser waste ('ash'), before the cleaned coal was dried, graded and loaded out.

Why it was used

Cleaning and grading coal at the pit made it worth more to buyers and let a colliery meet the tighter specifications increasingly demanded by industrial and domestic customers, rather than shipping stone and dirt along with the coal itself.

Mines associated with this term

Included only where MineArchive's own research gives a reasonable evidential basis — not every mine where this might plausibly apply.

• Ffos-y-Fran — Merthyr Tydfil (well documented example)
  Named in this record’s workings: “…method. Coal was moved by rail from the site to the Cwmbargoed washery, refurbished in 1992, and from there onward along the former Rhymney…”
• Pleasley Colliery — Derbyshire (well documented example)
  A large washery capable of handling 150 tons of coal an hour was added in the 1930s.
• Tower Colliery — Rhondda Cynon Taf (well documented example)
  A coal washery was added on the surface in the mid-1980s.

Sources

1. (secondary) Coal mining - Coal preparation — Encyclopaedia Britannica
2. (secondary) Coal preparation plant — Wikipedia

Record created: 31 August 2026 · Last researched: 31 August 2026