I attempted to make some hard sugar to use as windows for gingerbread houses. I thought I could do it without a candy thermometer as I have before, but obviously not. I tested it in ice water and it went straight from soft ball stage to a dry crumbly mess in a matter of 20 seconds. What did I do wrong?
It sounds like a stray sugar crystal fell into the mix--that's all it takes to kick off the crystallization you noticed. Ensure there is no undissolved sugar on the sides of the pan by wiping with a wet paper towel. Do so early though so you don't risk knocking them in at a susceptible point.