Why won't my slush freeze? 7 fixes that work
Runny slush or a solid block of ice? Here's what's going wrong in your slush machine and exactly how to fix it, from sugar levels to alcohol and temperature.
5 min read
1. Too much sugar
Sugar lowers the freezing point. A good slush sits at roughly 120–160 g of sugar per litre. Above that, the mix never sets and stays a cold, sweet juice. Juice, cordial and soda all count, not just the syrup you add.
2. Too little sugar
The opposite problem: with too little sugar the mix freezes into hard, crunchy ice that can stall the auger. Unsweetened juice, tea or watermelon often need a little syrup to get that soft, scoopable texture.
3. Too much alcohol
Alcohol freezes at a far lower temperature than water. Keep the whole batch under about 10% alcohol, which is roughly 30–40 ml of spirit per serving. Liqueurs count twice: they bring both alcohol and sugar.
4. Warm ingredients
Everything that goes into the machine should be fridge-cold. Room-temperature juice can add 20–30 minutes to the freeze time, and freshly brewed coffee or tea must cool completely first.
5. Wrong program or overfilling
Use the program the recipe recommends. Spiked programs run colder for alcoholic mixes, while milkshake and frappé programs keep dairy smooth. Never fill above the max line, or the machine can't move the mix fast enough to freeze it evenly.
6. A warm room
Slush machines need airflow. Keep at least 10 cm free around the vents and avoid direct sun. On a hot terrace the freeze can take noticeably longer.
7. Check before you pour
Not sure about your own creation? Our free Will-it-freeze calculator estimates sugar and alcohol for the whole batch and tells you whether it will set, before you waste a single drop.
Quick answers
- How long should a slush take to freeze?
- Most home machines need 15–60 minutes depending on the program, the amount and how cold the ingredients are.
- Can I fix a batch that won't freeze?
- Yes. Add cold water or unsweetened juice to dilute the sugar or alcohol, then restart the program.
- Does sugar-free soda work?
- Usually not on its own. Sweeteners don't lower the freezing point like sugar, so the mix freezes hard. Combine it with some regular juice or syrup.
