I use to take samples of wort and use a hydrometer to get the gravity readings. Then I decided to get a portable Refractometer. It was money well spent.
Refractometers take drops to give you a gravity read. I use a glass eye dropper and drop a few drops on the blue screen of the refractometer
I think I read somewhere when taking samples from boiling wort wait 30 seconds for the wort to cool. I leave the glass arm up while the wort sample is cooling. After the sample is cool I put down the glass arm.
Look in the view finder to see the wort, I originally learned to read wort in gravity. Not all refractometers read in gravity, most read in Brix.
I like using a refractometer because during the brewing process I can check the gravity as much as I want. I usually do get multiple gravity readings during the brewing process.
After fermentation using a refractometer is a little more tricky. Alcohol makes the readings slightly off. After my beer has fermented I get a few drops and get a reading. I use the following site to get the alcohol by volume here
When you start investing in home brewing equipment buying a refractometer is wort the cost.
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