On Sep 30, 1:25*pm, (Andrew Gabriel)
wrote:
White cement and building sand gives you yellow, without colouring.
Some building sand has quite a lot of (natural) surpless pigment.

I had a holiday job in the 60s, with a chap who was pointing the
stones on historic buildings. My job was to wash the sand to remove
bright colours. barrow, hose in bottom, getting wet all day long.
Fantastic job. I loved it.

Any that did not go grey we returned to the builders merchants, and
they brought us something else.