D.M. Procida wrote:

What can I do to make a parachute a little more impermeable to rain?
I've got one arranged over the hammock in the garden.

I don't want anything that will spoil its lovely soft billowing, and it
doesn't have to be completely impervious.

Daniele

Very hard to achieve without losing some flexibility.

Linseed oil thinned down may work.

Or whatever it is that they use on barbour jackets...