How to Use a Refractometer to Measure Specific Gravity

Summary

This video introduces the refractometer, a crucial tool for home and pro brewers to measure the specific gravity of wort by analyzing how light bends through a solution. Unlike hydrometers, refractometers require smaller samples and can track gravity changes during various brewing stages. However, once fermentation starts, readings get distorted by alcohol, so adjustments are needed using a calculator. Refractometers are essential for all-grain and partial mash brewers, offering pre- and post-boil gravity readings. The video also highlights how to use and calibrate the device, emphasizing its role in improving brewing precision.

Takeaways

• 🔬 Home brewers and professional brewers both use refractometers to measure specific gravity in wort.
• 💡 A refractometer measures the bending of light through a liquid to determine gravity, requiring only a small sample size.
• 📏 Unlike hydrometers, refractometers use a smaller sample and work by analyzing light refraction instead of buoyancy.
• 👁️ When viewing through the refractometer, a line splits a white and blue area, indicating the gravity of the wort.
• 📊 Refractometers can display readings in Plato or Brix, with some models showing estimated specific gravity alongside Brix.
• 🌡️ Temperature corrections for refractometers are accurate up to 86°F, so samples should be cooled for accurate readings if hotter.
• 🛠️ Refractometers are essential for partial mash, brew-in-a-bag, and all-grain brewers for tracking mash and wort gravity.
• 📦 Refractometers are factory-calibrated and ready to use straight out of the box, though instructions are included for future calibration adjustments.
• ⚠️ Once fermentation begins, alcohol distorts the reading, so a refractometer alone cannot determine post-fermentation gravity.
• 🔗 Northern Brewer provides an online refractometer calculator for accurate final gravity readings after fermentation.

Q & A

What is the purpose of a refractometer in brewing?

A refractometer is used in brewing to measure the specific gravity of wort by determining how the liquid bends light through a prism. It helps track the changing gravity of the mash and wort.

How does a refractometer work?

A refractometer works by using a prism to measure how light bends through a liquid sample. The bending of light, or refraction, helps determine the specific gravity of the liquid, which indicates the sugar content in the wort.

What is the advantage of using a refractometer over a hydrometer?

The main advantage of a refractometer is that it requires a much smaller sample size compared to a hydrometer, which relies on buoyancy and needs a larger volume of liquid.

How is the gravity of wort read on a refractometer?

When looking through the refractometer's viewfinder, a line marking the split between a white area and a blue area indicates the gravity of the wort.

What is the difference between the scales Plato and Brix on refractometers?

Some refractometers read gravity in Plato, while others use Brix. Brix is a common scale, and some models provide both Brix and estimated specific gravity readings.

Why should temperature be considered when using a refractometer?

Temperature affects refractometer readings. The tool can adjust for temperature up to about 86°F, but if the sample is hotter, the reading may be slightly inaccurate. It's best to allow the sample to cool before taking a measurement.

What types of brewers find refractometers particularly useful?

Refractometers are essential for partial mash, brew-in-a-bag, and all-grain brewers because they allow for monitoring the gravity throughout the brewing process, including during mash, sparge, and pre/post-boil stages.

Is calibration necessary for new refractometers?

No, calibration is typically not necessary for new refractometers, as they are factory-calibrated before being shipped. However, instructions for calibration are included in case adjustments are needed later.

Why can't a refractometer be used to measure gravity during or after fermentation?

Once fermentation begins, the alcohol produced distorts the refractometer's reading because it affects how light bends through the solution. Therefore, a refractometer alone cannot accurately measure gravity after fermentation.

How can brewers adjust refractometer readings for fermented beer, wine, or mead?

Brewers can use a refractometer calculator, like the one on the Northern Brewer website, to adjust their readings. By inputting the original Brix reading and the reading during or after fermentation, the calculator converts it to specific gravity.