Refractometers are very useful tools for advanced brewers, but they can also benefit new brewers as well, if used properly.
Like a hydrometer, a refractometer measures the amount of sugar content in a solution. Refractometers use refracted light to determine the amount of sugar in a solution, while hydrometers measure the density to determine the amount of sugar in a solution. They take a bit more calibration and adjustments than a hydrometer, but they also use MUCH LESS wort/beer in a sample.
Our refractometer also features Automatic Temperature control so you do not have to do any temperature adjustments. However, there are some adjustments that will need to be made for accuracy when using with wort/beer.
Refractometer includes comprehensive instructional booklet as well, but as always if you have any questions, please contact our Amazing Customer Service Reps
Click Here for Printable Instructions
To be accurate, you will need to calibrate your refractometer using distilled water. To calibrate:
1. Lift up the sample plate and add a few drops of distilled water making sure the whole glass surface is covered.
2. Close the sample plate and make sure there are no bubbles.
3. Hold the refractometer up to natural light and take a reading.
4. The reading should be at 0. If it’s not, you may need to raise or lower the calibration screw (under the small black rubber cap) at the top of the refractometer using a small screwdriver.
5. Adjust the screw until the reading is at 0.
Your refractometer is now calibrated.
Taking a Reading:
- Place a few drops of the sample to be tested (beer or cider) onto the main prism, close the daylight plate (sample plate) and check reading. Take the reading where the boundary line of blue and white cross the graduated scale.
- The scale will provide a direct reading of the concentration. You will have to make some of the following calibrations and adjustments once you have your reading.
Refractometers are designed to measure the amount of sucrose or fruit sugar (fructose) in solution. Beer wort, has a different density and contains more complex sugars than sucrose or fructose. It refracts light differently so an adjustment is needed for accuracy. This is called “wort calibration”, or a “wort refractive index (WRI) correction”
Refractometers may vary between brands, but the average wort correction factor for most refractometers and beers is 1.04 Brix (not SG). So you will divide your refractometer Brix by 1.04 to get your actual reading. For example, if your reading is 14.6 Brix then your corrected reading is 14.04 Brix (14.6/1.04=14.04). Then, we can convert the measurement in Brix to specific gravity.
This calculator from our friends over at Brewer’s Friend is very useful and can help you find your WRI correction, found here. (Use the “Part I” calculator for WRI corrections.)
If you would like to find out the exact wort calibration for your refractometer over several batches a more detailed method is explained here.
Note: Wort Calibration is only important if you really want an accurate reading for an exact OG or to find your ABV. It is not necessary when taking final samples to check if fermentation is complete (more on this below).
Final Gravity Corrections:
Because refractometers use refracted light to take Brix/SG readings, the become less accurate when alcohol enters the picture because, like sugar, it also has a refractive index and this can throw off the accuracy. Fortunately, there is a correction calculator for this, too, as long as you also have your wort correction factor from above.
You can find that calculator on the same Brewer’s Friend page here. (Use the Part II Calculator for FG corrections.)
Determining the End of Fermentation:
Your refractometer can tell you if your beer is done fermenting with only a few drops over the course of a few days. In fact, this will probably be the main use of your refractometer with our Mr. Beer kits. If you’re unsure whether your beer is done fermenting or not, use the following steps:
- Take a Brix reading and write it down.
- Wait 24 – 48 hours and take another reading and compare with the first.
- If there is no change in readings, then your beer is done and you can skip the next steps. It’s time to bottle.
- If there is a change in readings, then your beer is still fermenting.
- Wait a few more days and repeat the steps until the readings are consistent and do not change.
Pros and Cons:
- Uses much less wort/beer in a sample than a hydrometer.
- More portable, durable, and rugged than a hydrometer.
- Features Automatic Temperature Control and does not require temperature corrections.
- Can take pre-boil and post-boil Brix/gravity readings at any temperature so you can adjust sugars, as needed.
- Can take accurate gravity readings of fruit juices so you can make adjustments, as needed.
- Not as accurate as a hydrometer without making some adjustments (see above for adjustments and corrections).
- Final gravity readings require adjustments due to the presence of alcohol.
- Needs to be calibrated every so often (after every use is recommended for accuracy).
- Can sometimes be difficult to read under artificial lighting (natural lighting is best).
- Make sure your wort is mixed really well before pulling a sample.
- When taking readings, be sure the whole surface of the sample area is covered and there are no bubbles under the sample plate when closed.
- Use the steps outlined above, and the Brewer’s Friend calculators for more accurate readings.
- Rinse and dry refractometer after every use.