Por Que Suas Leituras no Refratômetro Variam Tanto? E Como Melhorar

Summary

In this video, the presenter demonstrates the correct use of a refractometer to achieve accurate, repeatable, and consistent measurements in brewing, particularly in comparison to using a hydrometer. The video highlights common issues with refractometer readings, such as inconsistencies, and offers practical tips to overcome these challenges. Key points include the importance of calibrating the refractometer, proper techniques for cooling the sample, and the need for using correction factors to account for different types of sugars and alcohol in the brew. The video emphasizes that with the right technique, a refractometer can be an indispensable tool for precise brewing measurements.

Takeaways

• 😀 Refractometers are essential tools for brewers, offering a faster and more compact alternative to hydrometers, but they require proper calibration and handling to give accurate readings.
• 😀 Inconsistent readings with a refractometer are often due to improper usage, such as incorrect temperature or the technique of blowing on the sample to cool it down.
• 😀 Proper calibration is crucial—refractometers should be calibrated with water to ensure the readings start at zero before taking measurements.
• 😀 The refractometer is not an absolute instrument and can show inaccurate readings when used outside its calibration temperature, typically 20°C.
• 😀 To minimize errors, it is recommended to use a pipette to collect the sample and avoid altering the composition by blowing on it.
• 😀 For accurate measurements, after collecting the sample, it should be cooled in a cup of water to the correct temperature before testing.
• 😀 Cleaning the refractometer is vital to avoid residue contamination that could skew future readings.
• 😀 Refractometers measure the deviation of light caused by substances in the liquid. Alcohol and sugar both cause light to deviate, but alcohol has a stronger effect on the readings, especially in fermented beer.
• 😀 When using a refractometer to measure fermented beer, the alcohol content affects the readings, and a correction factor (typically 1.04) should be applied to obtain the real sugar concentration.
• 😀 Calculators can help correct refractometer readings for fermented beer. The corrected density can be determined by inputting the original sugar concentration and the refractometer's reading into online tools.

Q & A

What is the main advantage of using a refractometer over a hydrometer in brewing?

The refractometer requires only a small sample size and provides faster readings, which is particularly useful during boiling or when limited sample volume is available. In contrast, a hydrometer requires a larger sample size and a temperature adjustment to get an accurate reading.

What is the first thing to do before using a refractometer to ensure accurate readings?

The refractometer must be calibrated before use. This is done by placing a drop of distilled or tap water on the prism and ensuring that the reading is at zero. If not, the calibration screw should be adjusted.

Why is blowing on the sample to cool it down not recommended when using a refractometer?

Blowing on the sample can alter its composition by dragging liquid away, which concentrates the sugars and results in inaccurate readings. It is important to cool the sample properly using another method.

What is the proper method to cool a hot sample before measuring with a refractometer?

To cool the sample, place it in a small glass of water. This method allows the sample to cool quickly to the correct temperature without affecting its composition.

How can you ensure that the refractometer doesn’t give inconsistent readings?

Consistency can be achieved by using a pipette to transfer the sample, ensuring no external air or heat is introduced, and by ensuring the sample is at the correct temperature before taking the reading.

What is the correction factor commonly used to adjust refractometer readings for different sugars in beer?

A correction factor of 1.04 is commonly used to adjust the refractometer readings, particularly for beers that contain a mix of sugars like maltose, glucose, and sucrose. This factor accounts for the differences in refraction between these sugars.

Why does alcohol in the beer affect the refractometer readings?

Alcohol also bends light in a similar way to sugars, but it bends light more intensely. This leads to higher readings in finished beer, which can be misleading if not properly corrected.

How can you correct refractometer readings for alcohol content in finished beer?

To correct refractometer readings for alcohol content, use a calculator specifically designed for fermented beer. These calculators take into account the original gravity and the alcohol content to provide an accurate final gravity reading.

Why is it important to know the original gravity (OG) of your brew when using a refractometer?

Knowing the original gravity is important because it allows you to calculate the attenuation and correct the refractometer reading for alcohol content. Without this, you would not be able to account for the impact of fermentation on the final reading.

What tool can help you correct refractometer readings for fermented beer accurately?

Refractometer calculators, such as those available online or in brewing apps, can help correct the readings by inputting the original gravity (OG) and the refractometer’s reading after fermentation. These calculators adjust for the presence of alcohol.