Make a lactometer with ball point refill. What would you do to make the refill stand vertically straight ?

Explanation

1. Take an empty ball pen refill. It should have a metal point.
2. Take a boiling tube and fill it with water.
3. Put the refill in with metallic point inside the water.
4. Use a pen to mark the point on the refill to show the part which is above the water surface.
5. Pour out the water from the boiling tube and fill it with milk.
6. Float the refill in the milk.
7. Put the record mark on the refill, at the point showing the part which is above the surface of the milk.
8. These two marks are not at the same place. This is the improvised lactometer.
9. We have to attach a small weight at the bottom of the refill to make it stand vertically straight.