1) A native salt which was used as a flux in welding and as a mild alkaline solution in cleaning.

A cutler called John Shirtcliffe had a parcel of boreax in the closet adjoining his Work Chamber in 1713. It was used by coiners: 1684 two paire of little weigh-scales, one file with bright fileings in, like the fileings of silver and two peices of burras, Halifax.

spellings burras
dates 1684 1713

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