neutral colourant ?

[McCrunchy]

Hello,

 

I'm looking for a colourant that's soluble in water, is chemically mostly inert, and washes away easily. I just want to visualize some flows. I used to use KMnO4, but it is obviously not very inert, to say the least ...

 

Thanks for your suggestions,

 

McCrunchy

[UC]

i think sodium fluorescein is typically used for applications like this.

[insane_alien]

food colouring would probably work fine.