OK, how about if I drop the alcohol and replace it with an oil?

If I remember correctly, oil and water will try to stay separate,
and oil is lighter than water...
Only the higher surface tension may be an issue....

What about water and petrol....??

Anyway, water is not strictly necessary. The concept only calls for two
non-mixable fluids with significantly differing density.

Ventilator: check my final note on my above post. The valve
at the top should stop what you say...