Calibrate Your Brewing Instruments

Raise your hand if you’ve ever actually verified that your hydrometer measures gravity accurately.

I never gave it much though either.

Then one day I was buying a couple of new hydrometers – to replace the several that I broke of course – and decided to give it a try.  Out of the box, one hydrometer was off by 2 points, the other by 3…

Hardly the end of the world, but when you’re trying to hit those gravity numbers exactly, the accuracy of your instruments is at least a little relevant.

Thermometers are even worse.

I have one of those long-stemmed kind, with the analog dial.  I use it for checking mash temperatures because it’s easy to move around in the mash and make sure the temperature is even throughout.  4 or 5 degrees difference is again sort of a big deal when you’re trying to hit a specific mash temperature.

I swear it needs to be calibrated every other time I use it.  Between getting bumped, stirred and just plain tossed around it’s almost always off when I check it.

So we know it’s something that needs to be done.  But how?  And how often?

Calibrating your instruments sounds like kind of a pain, but it’s actually pretty simple.

Hydrometers

These are the easiest because it only needs to be done once.  There’s no adjustment on the standard “glass with lead weight and paper scale” type.

Get a jug of distilled water from the grocery store – make sure it’s distilled, not spring or drinking water. The mineral and ion content will throw off the reading otherwise.

Next, check the calibration temperature on your hydrometer.  It’s usually 60ºF but it should be labeled somewhere on the scale.

Pour a sample of the distilled water into your hydrometer jar and make sure it’s at the correct temperature. Put it in the freezer or somewhere warm for a couple of minutes if not.  It needs to be pretty exact or the reading will be off.

Then just take a reading with the hydrometer.  It should read 1.000 exactly. If not just make a note of the difference and adjust your wort/beer readings accordingly.

Unless it becomes damaged, the hydrometer shouldn’t change from it’s original calibration.  So you should only need to test it once.

Refractometers

Just like the hydrometer.  Take a sample of distilled water at the calibration temperature – again usually 60ºF (the scale should show the temperature) and make sure it reads 0 Brix.

Many models have a calibration screw you can adjust if it’s incorrect.  If yours doesn’t then just make a note of the difference and apply it to future readings.

Thermometers

The standard way to check your thermometer is to put it in a cup of ice water, which should read 32ºF and then into a pot of boiling water which should read 212ºF (depending on your elevation above sea-level).

That never works for me.

When I set the dial to 32º in the ice water – boiling is off the scale.  Same thing happens when I do it the other way around.  Besides, I’m not trying to measure boiling or freezing- I want to measure things in between.

So I’ve found an even easier way. I bought a glass lab thermometer for $8 at the homebrew store.  This one I verified to within 2ºF at both freezing and boiling.

Now, when I’m heating the mash water at the beginning of the brew day I use the lab thermometer to take a reading at about 150ºF and then calibrate my other thermometers to that. Since I’m just waiting for the water to heat anyway there’s no extra time invested in making a quick check.

Testing your equipment doesn’t have to be time consuming or difficult.  But making sure you’re taking accurate measurements each time is one more piece of puzzle that is consistently brewing high quality beer.

Photo by Kevin Dooley

Tagged as: brewer, hydrometer, instruments, refractometer, thermometer