Naked Light

Any unshielded flame carried underground for light — a tallow candle, an open oil lamp, or a torch. Before the safety lamp there was nothing else, and in a mine carrying firedamp a naked light is an ignition source moving about the workings at head height.

Historical usage

Miners took open flames underground as a matter of course, and the phrase 'naked light' enters the record mainly through the reports written after they set something off. It is a standing presence in the disaster accounts in this archive. Sir Roger Mostyn's account of the firedamp explosion at Mostyn Colliery on 3 February 1675 is among the earliest first-hand descriptions anywhere of what such an ignition does. The Felling pit disaster of 1812 near Gateshead, in which 92 men died, was among the stimuli for inventing a lamp that would give light without igniting gas, and the Davy lamp, the Geordie lamp and Clanny's lamp followed. Prohibition did not follow neatly from invention. Rules requiring safety lamps were in principle strict but in practice were neither observed nor enforced, because miners preferred the better light a naked flame gave. The compromise reached in many pits was geographic rather than absolute: at Trimdon Grange in 1882 the official report records that the only lamp in general use was the old Davy pattern, and that naked lights called 'midgies' were carried by the driver boys and permitted as far as caution boards set at a safe distance from the working places.

How it worked

A candle was fixed to the hat, wedged in a crevice, or stuck to a timber with its own tallow. Beyond lighting, the flame was also an instrument: before safety lamps, a candle was the standard test for firedamp. The candle was trimmed and the excess fat removed, held at arm's length at floor level with the other hand shielding all but the tip of the flame, and raised slowly while the tip was watched. If it stayed unchanged the air was safe; if it turned bluish-grey and drew up into a thin extended point of deeper blue, firedamp was present.

Why it was used

Light. A naked flame is far brighter than the same flame behind gauze, and the safety lamp's gauze cut its output badly — which is exactly why men went on using candles in pits where they were forbidden. In a mine known not to be gassy, or in the parts of a gassy mine thought safe, a naked light was simply the cheapest and best illumination available.

Risks & limitations

It ignites firedamp, and firedamp is explosive between roughly five and fifteen per cent in air. That is the whole of the risk and it is sufficient. The disaster records in this archive turn repeatedly on where naked lights were permitted, how far the caution boards stood from the face, and whether anyone had checked the air lately. A naked light is also useless as a warning: unlike a safety lamp, whose flame lengthens and blues in gas and can be read by anyone trained to look, an open candle carried into a body of firedamp gives no notice at all before it fires it.

Related terminology

Deputy, Firedamp, Overman, Safety Lamp, Shot-firing

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.

• Usworth Colliery — Tyne and Wear (well documented example)
  Named in this record’s history: “…colliery's record. On 5 June 1850 an outburst of gas ignited by a naked light killed thirteen. On the evening of 2 March 1885 a build-up of…”

Disasters associated with this term

5 examples chosen from 8 linked records, most direct relationship first.

• Big Pit explosion (1908) (contextual relationship)
  Named twice in this record, first in the cause: “A coroner's court found the explosion was caused by a naked light — an open flame, probably from a miner's lamp — held by one of the…”
• Fochriw Colliery Explosion, 1902 (contextual relationship)
  Named 3 times in this record, first in the summary: “…a body of firedamp at Fochriw Colliery, which was ignited by a naked light, killing eight miners.”
• Gethin Colliery explosion, 1862 (contextual relationship)
  Named 3 times in this record, first in the summary: “Gas ignited at a naked flame in the No. 19 heading of Gethin's Lower pit on 19 February 1862,…”
• Grove Pit Disaster, 1930 (contextual relationship)
  Named in this record’s cause: “An underground gas explosion, most likely triggered by a naked light — the inquiry found that five of the dead were carrying contraband…”
• Llanerch Colliery Explosion, 1890 (contextual relationship)
  Named in this record’s cause: “A naked light igniting an accumulation of gas in the No. 4 level off Cook's slope,…”

Sources

1. (primary) Report of T. W. Snagge on the Explosion at Trimdon Grange Colliery, 16 February 1882 — The National Archives
2. (secondary) Safety lamp — Wikipedia

Record created: 3 September 2026 · Last researched: 3 September 2026