I'm looking at a recipe for condensed milk, and a couple of the steps say the following:

Do not stir once the mix starts to simmer otherwise it can crack and crystalize.

if there are sugary bits hanging around the rim of your pot don’t stir them into your condensed milk, this can also crack your mix

I'm not sure what "crack" means for a liquid.

  • 3
    Personally I would assume it means 'split', and is either a slight mistranslation or a synonym I haven't encountered.
    – OJFord
    Commented Nov 28, 2023 at 14:50
  • 2
    @OJFord The usual term is for a sauce to "break", although Google ngrams does show "split sauce" gaining in popularity on "broken sauce". "Cracked sauce" doesn't even appear, although "sauce cracked" has a very odd surge in popularity around 2010 for some reason. Commented Nov 28, 2023 at 15:07
  • @NuclearHoagie split seems more common than break in British English (or at least Southern English English)
    – Chris H
    Commented Nov 29, 2023 at 10:26
  • My wife is a UK manufacturing pharmacy technician. They talk about emulsions 'cracking'. It is irreversible. Commented Nov 29, 2023 at 11:56
  • @NuclearHoagie I've never heard 'break' either, am also BrE speaker so as ChrisH alludes to perhaps it's regional. (Except as in 'hot break', 'cold break' in homebrew especially but works for milk or stock too.)
    – OJFord
    Commented Nov 29, 2023 at 17:35

1 Answer 1


Roughly, it means for the liquid to separate into two distinct portions which won’t readily recombine. In this case, it’s referring to the sugar crystals causing the supersaturated sugar solution that is your milk to crystallise out. Other examples include boiling coconut cream down for Thai curry, or adding the oil too quickly when making mayonnaise. In both of these cases, “cracks” in the mixture appear as transparent oil separates out from the opaque mixture.

  • 1
    I wonder if this term is borrowed from the petroleum cracking process
    – ihatecsv
    Commented Nov 28, 2023 at 13:59
  • 6
    @ihatecsv It’s an interesting thought, but I suspect the cooking terminology predates that, and the two processes have little in common.
    – Sneftel
    Commented Nov 28, 2023 at 14:16
  • 1
    @ihatecsv - no, it's not.
    – Fattie
    Commented Nov 28, 2023 at 14:52
  • 2
    @Yorik yes, but that refers to letting a drop of the super-heated sugar solution fall into cold water and seeing what happens. (thespruceeats.com/soft-crack-stage-520377) Not to things happening in the mixing bowl. Commented Nov 28, 2023 at 23:31
  • 1
    @ihatecsv if here was a connection, I'd think it would be the other way round, but I doubt they're linked
    – Chris H
    Commented Nov 29, 2023 at 10:26

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