Met History wrote:

> "/Unglazed red and black wall tiles and all unglazed paving tiles
> should be oiled before setting as follows: Pour boiled or raw linseed
> oil to a depth of a quarter of an inch into a shallow tray, (in the
> style of a bread pan, 2 feet or more square--for large jobs a tray 4
> feet square will be found convenient,) let the tiles rest face
> downward in the tray for at least one minute. Avoid splashing oil on
> the backs of the tiles which are expected to retain their full
> porosity and adhesiveness in cement and mortar. After removing from
> the tray, wait at least 5 or 10 minutes until the tiles absorb the
> oil. (if several days intervene, so much the better.) Then soak the
> tiles in water as usual and set them/."
>
> Henry Chapman Mercer ca 1920
>
Interesting technique.

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