Hi, Steve,

Viewing Tyndall Effect is better done in the dark.
But for a comparison, it is even more important to
shine the laser through two identical containers at
the same time, side by side, and then move
the laser around so it shines through both again
but in opposite direction.

The two identical containers would hold samples
before and after  dilution, making a comparison as
objective as possible.

Best regards,

Matthew