I am making a small (desktop) wind tunnel for educational purposes, I want to have 10 fairly thick smoke-streams about 3cm apart. I have experimented with incense but the stream is not thick enough and barely visible.
I was thinking of using a pipe with holes drilled in it to get the 10 smoke-streams, the low pressure of the airflow drawing the smoke out through the pipe from a container with the burning substance.
What can I burn that will produce a nice thick white smoke and is non-toxic?
Is there a different/better way to get non-toxic 'smoke' without burning anything?
Is the pipe a good way to distribute the smoke or are there any other/better techniques to getting the multiple streams?