Waterproofing a Blanket

Don't let yesterday's rainstorm dampen your plans for a picnic. You can waterproof a cotton or wool blanket by adding a protective backing of water-resistant fabric such as ripstop nylon or oilcloth, and safely lounge on damp grass.

Martha Stewart Living, June 2001 http://www.marthastewart.com/265788/waterproofing-a-blanket