January 10, 1709

Abraham Darby I

Coalbrookdale Furnace Begins Its Coke-Fueled Campaign

Darby's accounts preserve a documentary fingerprint: coal being 'charcked' in early January, and no wood or charcoal purchased for the furnace campaign.

Brought into blast

The traditional account places the bringing-into-blast of Abraham Darby's refurbished Coalbrookdale furnace on 10 January 1709, fuelled by coke — contemporary accounts call it charked coal.

Darby had leased the damaged Shropshire furnace in 1708, repaired it and prepared coke from local coal. His surviving accounts document coal being charcked in early January and contain no purchases of wood or charcoal for the campaign, which is strong evidence that coke was used.

Blast is not the same as cast

A furnace must be heated and operated before its first cast, so brought into blast and successfully produced cast iron are not interchangeable events. The evidence does not securely establish that finished cast iron was produced on 10 January itself.

One reconstruction identifies an item entered about four weeks after furnace warming as the probable first cast. Contemporary English dating also used the Julian calendar; 10 January Julian corresponds to 21 January Gregorian.

What Darby was actually first at

He was not the first person to try coke or coal in iron smelting. What is well supported is commercially sustained production of coke-smelted iron at Coalbrookdale beginning in 1709.

The commercial target was cookware: grey cast iron suitable for thin pots made efficiently in green-sand moulds, a system he developed with the moulder John Thomas. Darby sold 81 tons of iron goods during 1709, and the oldest identified surviving Darby coke-iron pot is dated 1714.

Sources

Researched 23 Aug 2026 8 sources 2 audit passes Date disputed

How this was checked

Researched from the web into a fact sheet, rewritten from that sheet, then audited against it by a different model. How the pipeline works →

Date disputed. Sources disagree; the research places it at ~1709-01.

What the sources leave uncertain

The year 1709 and coke use are strongly supported. The exact innovation date remains disputed in economic and technological histories.
The often-repeated 10 January date appears to identify bringing the furnace into blast or beginning its campaign, not necessarily the moment usable cast iron first flowed.
A furnace must be heated and operated before its first cast, so “brought into blast” and “successfully produced cast iron” should not be treated as interchangeable events.
Contemporary English dating used the Julian calendar and a legal year beginning on 25 March. Modern accounts normalize the year to 1709; 10 January Julian corresponds to 21 January Gregorian.