Treated or designed to resist penetration by grease, oil, or fat without tearing or absorbing.
From 'grease' + 'proof' (from Old French 'prover' meaning to test); the term emerged in the early 20th century for specially treated papers and materials that could repel oil without being destroyed by it.
Greaseproof paper was a revolution in baking and food packaging—it looks fragile but its waxy coating creates a nearly invisible barrier that stops oil from seeping through. The same material principle is used today in everything from burger wrappers to non-stick pans!
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