To turn Water to Milk and back again......very simple method

White fluids representing milk, etc., may be formed by
mixing soluble salts (in solution) with suitable agents, so
that the final result shall give a white precipitate in
suspension ; but the results differ much in appearance
and only a few salts are suitable. Soluble calcium salts,
as calcium chloride, are rendered insoluble, forming white
deposits with sulphates or carbonates, as sodium carbonate
or sodium sulphate. Soluble silver salts act in the same
way with chlorides, such as sodium chloride; as do also
the soluble salts of lead. Mercury salts and ammonia
give like results, and magnesium hydrate and sodium or
potassium hydroxide give heavv curdy precipitates
take one or two of the best:—
(1) To form a fluid resembling milk, mix strong
solutions of calcium carbonate and sodium carbonate;
to clear it, use hydrochloric acid.
(2) Use nitrate of silver and a saturated solution of
pure chloride of sodium; this is cleared by ammonia.
Avoid shaking, or the milk goes into curds at once.
The chloride of sodium must be pure—common salt is no
good.
(3) Sulphurous acid and acetate of lead, which is
cleared by strong nitric acid.