In An Experiment concerning the Spirit of Coals, a letter to Robert Boyle from John Clayton, Boyle writes

At first there came over only phlegm, afterward a black oil, and then likewise a spirit arose which I could noways condense; but it forced my lute, or broke my glasses. Once when it had forced my lute, coming close thereto in order to try to repair it, I observed that the spirit which issued out caught fire at the flame of the candle, and continued burning with violence as it issued out in a stream, which I blew out and lighted again alternately for several times.

A quick google search returns only this passage of the letter. Does it literally mean "broke my glasses", as forced my lute, or broke my glasses would imply?

  • 2
    The "or" seems to come from repeated attempts where it either "forced the lute" or "broke glasses." Commented Jul 1, 2021 at 16:42
  • 3
    You just watched youtube.com/watch?v=F3rncxf4Or8 didn't you. Commented Jul 2, 2021 at 21:01
  • 2
    @Shufflepants All praise the mighty Youtube Algorythm - what's the bet everyone who views this question ends up with that recommendation in their youtube feed now?
    – Criggie
    Commented Jul 2, 2021 at 23:21

3 Answers 3


I don't think the glasses here are spectacles or eye-glasses. I think they are vials or flasks of some sort. Clayton is experimenting with coal and it's produced a high-pressure vapour.

OED has


Tenacious clay or cement composed of various ingredients, and used to stop an orifice, to render air-tight a joint between two pipes, to coat a retort, etc., and to protect a graft. Also with a and plural a particular kind of this substance. †lute of wisdom [= medieval Latin lutum sapientae] , a composition for hermetical sealing, variously described by alchemists.

The pressure was sufficient to break the seal or, if the seal remained intact, it damaged the flasks.

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    I speculate that "broke" in this case means "escaped" (we still use "break wind" as an archaic holdout of this usage) rather than "destroyed."
    – noneuklid
    Commented Jul 2, 2021 at 8:45
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    I have encountered "lutum" in several variations a couple of times when reading up on alchemy and early chemistry a few years ago. "Broke through the lutum" or 'Escaped the lutum seal". Had to look up the meaning too then, but that second variation made it clear that is had to be some kind of sealant. I don't recall seeing "lute" used, but it makes perfect sense.
    – Tonny
    Commented Jul 2, 2021 at 8:52
  • @noneuklid And also "break out" as in jail.
    – Barmar
    Commented Jul 2, 2021 at 18:24

This question first arose following the release of How the gas mantle made lamps 10x brighter by Technology Connections, and it seems they've found a likely answer.

We found what “forced my lute” meant! Back in ye olde chemistry days, lute was a substance used to make seals between your various chemistry apparatus. So, Clayton was probably saying the 330 year old equivalent of “blew the seals” (or indeed, the pressure was sufficient to break the glass!).


Per Wikipedia,

Lute (from Latin Lutum, meaning mud, clay etc.)[1] was a substance used to seal and affix apparatus employed in chemistry and alchemy....

Another use for lute was to act as a safety valve, preventing the buildup of vapour pressure from shattering a vessel and possibly causing an explosion. For this purpose, a hole was bored in the flask and covered with luting material of a particular composition, which was kept soft so that excessive buildup of vapour would cause it to come away from the vessel, thus releasing the pressure safely.¹

From this it seems clear that "forced my lute, or broke my glasses" means that:

  • the increase in pressure forced the luting material from the hole, opening it and releasing the pressure, or instead
  • this luting safety mechanism did not work and the glass itself broke under the strain.

¹ The reference given for this is: Encyclopædia Britannica. Eighteenth Century Chemistry as It Relates to Alchemy (reprinted Kessinger Publishing, 1992) p. 78-79.

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