Take the rank oil and put ten pints into a jar and make a mark on
the jar at the height of the oil; then add to it a pint of vinegar
and make it boil till the oil has sunk to the level of the mark and
thus you will be certain that the oil is returned to its original
quantity and the vinegar will have gone off in vapour, carrying with
it the evil smell; and I believe you may do the same with nut oil or
any other oil that smells badly.
631.
Since walnuts are enveloped in a thin rind, which partakes of the
nature of ..., if you do not remove it when you make the oil from
them, this skin tinges the oil, and when you work with it this skin
separates from the oil and rises to the surface of the painting, and
this is what makes it change.
632.