veil workshop musings

I've been asked to do a short (1.5 hr) veil dying workshop.

On the one hand, yay!
On the other hand: uhhhh...

I have to figure out how much to charge per person for this. I would be supplying all the stuff, from silk to vinegar to dye to a microwave, plus all the plastic doodads one needs to mix, zap, and protect oneself from the dye.

Should I go through and add up all my costs for these items, then add some mysterious percentage for myself? Or..?

The timing is a little tricky as well... in 90 minutes, how many students
can
--set up a draped space to work
--listen to 10 minutes of lecture about fiber reactive dye
--soak their silk in vinegar
--mix their dye
--dye the silk for (say) 15 minutes
--line up to zap their items in the microwave
--rinse and rinse and rinse their items in the nearest sink? (And will the
location go ballistic over that?)