Here’s the geeky bit (I promise it’s funny): starch molecules are hydrophilic, which means they love water like a Labrador loves a tennis ball. When you heat them, they swell, burst, and tangle into a web. That web traps water molecules, so your liquid gets thick—not because you’re magic, but because starches party with H2O. Also, acids like wine or lemon juice prevent thickening, so if your sauce is runny and you added lemon, congratulations—you’re the enemy of starch.
Water And Flour Thickener at Nathan Brodzky blog
One more shocking fact: the longest gravy train in history was 2.7 miles long, made with 400 gallons of gravy in the UK. I guarantee they used a butt-ton of cornstarch. You’re welcome.
