The other thing is the sand - most builder's sand has loads of
iron oxide in it (which is what makes it yellow/orange) and it
will end up looking bright yellow through to dull orange regardless
of any white cement/line you use. You can get better washed sand
which is lighter in colour (silver sand), and you should look for
that. Don't use sandpit sand - it can be too rounded off to bind
well (to reduce scratching in eyes).


Pretty easy to wash out the yellow (ochre rather than oxide I think).
The sand settles quickly and the yellow stays suspended in the water for
several minutes, so is easy to pour off