---
title: "The Ice-Water Test: A Five-Minute Check on Your Temperature Probe"
url: https://fizzwizz.ca/ice-water-test/
date: 2026-10-15T07:41:39+00:00
modified: 2026-10-15T07:41:39+00:00
lang: en_US
---

# The Ice-Water Test: A Five-Minute Check on Your Temperature Probe

FizzWizz calculates finish pressure from the product temperature. If the probe reads warm, FizzWizz calculates less CO2 than the product needs and the beverage ends up under-carbonated. The fix is a five-minute check you can do with a cup of ice.

## Why one degree matters

At a fixed pressure, CO2 solubility in water changes by roughly 0.08 volumes per degree between 0 and 5°C: about 2.69 volumes at 0°C versus 2.30 at 5°C at 10 psig ([University of Florida IFAS](https://ask.ifas.ufl.edu/publication/FS379), calculated for water). A probe that's one degree off moves your finished carbonation by about that much. That's the difference between on-spec and a customer asking why the beer is flat.

## What you need

- A large cup or insulated container
- Crushed ice (more is better)
- Cold, clean water
- Your WizzTemp probe, removed from its thermowell

Do this between runs, not while the FizzWizz is carbonating, since the probe has to come out of the tank.

## The steps

![Four-panel illustration: fill with ice, add water, insert probe, wait for a steady reading.](https://fizzwizz.ca/wp-content/uploads/2026/10/03-inline-four-steps-1024x743.jpg)

This follows the standard ice-point method used in food safety ([Wisconsin DATCP](https://datcp.wi.gov/Documents2/ThermCalibrationInfographic.pdf)):

1. Fill the container completely with crushed ice.
2. Add cold water until the container is full, then stir.
3. Put the probe into the ice water so the sensing tip is fully submerged and not touching the bottom or sides.
4. Wait at least 30 seconds, or until the reading stays steady.
5. Read the temperature on the FizzWizz display. It should read 0°C.

If ice starts to float clear of the probe, pour off a little water and add more ice so the tip sits in slush.

## How far off is too far?

A well-made ice bath sits very close to 0°C. Fluke, which makes calibration equipment, gives the ice-point method an accuracy of about ±0.1°C, but describes it as a quick field check rather than a formal calibration, because it tests only one point and depends on a careful setup ([Fluke](https://www.fluke.com/en-ie/learn/blog/calibration/calibrate-digital-thermometer)).

For carbonation, one point is the right point: your product sits within a few degrees of 0°C. If the probe reads 0°C in the bath, you can trust it in the tank.

## If the reading is off

If the probe reads more than a few tenths of a degree away from 0°C, [contact us](/contact/) before your next run.

## When to check

Check the probe when you first install it, after it's been knocked or dropped, and whenever a run comes out under-carbonated for no obvious reason. A probe that reads warm is one of the first things worth ruling out.

## Sources

- Wisconsin Department of Agriculture, Trade and Consumer Protection, [Calibrating a Thermometer](https://datcp.wi.gov/Documents2/ThermCalibrationInfographic.pdf) (ice-point procedure).
- Fluke, [How to Calibrate a Digital Thermometer](https://www.fluke.com/en-ie/learn/blog/calibration/calibrate-digital-thermometer) (accuracy and limits of the ice-point method).
- University of Florida IFAS, [FS379](https://ask.ifas.ufl.edu/publication/FS379), Table 2.
- FizzWizz [How It Works](/how-it-works/) and [FAQ](/faq/) (a probe reading warm causes under-carbonation).