LUSH Henna - can I grate it with a metal grater?!

[TheBrilloPad]

Everything says not to let the henna touch metal or it turns your hair green, but how do I cut up the block without using a metal knife or grater?? Or is it just when it's mixed that you can't use metal?

I used the metal grater attachment for the food processor, turned it to powder so melted very easily.
Have also chopped it with a knife before and melted it on a bain marie

No green hair here!

It doesn’t really need grating. I just chop mine on a chopping board.

I just chop mine into blocks, pour on water and heat until they disintegrate - doesn't take long.

But you all use a metal knife to chop, and it's fine, yes? I read you can't use metal and can only use plastic and wood so couldn't figure out how to cut without a metal knife!

A metal knife, yes, and no green hair so far :)

I think it's if you heat it in a metal pan it reacts