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Triple Scale Hydrometer Accuracy

A pattern has emerged on my last few brew days: mash+lauter efficiency has dropped. So I decided to do some basic troubleshooting. Have I changed any procedures? No. Equipment? Yes. I purchased some “precision” hydrometers and have used them on my last three batches.

So I decided to test my old and new hydrometers. It turns out that the triple scale hydrometer

I have been using all along was off by four points. Here’s the surprising thing: ALL THREE of my triple hydrometers are off by exactly 4 points! My new precision hydrometers are dead on.

Shame on me! I tested my hydrometer when I first started brewing, and I remember it being off. I didn’t care though. I figured as long as I use the same hydrometer to test OG and FG, the outcome would be the same whether or not I compensated for hydrometer being off. I still think that’s sound logic, but only for extract brewing. That logic does not hold in all-grain brewing when you are taking gravity readings to check your mash efficiency. I knew better. I was just being lazy.

I would have went with a refractometer rather than precision hydrometers.

How did you test the hydrometers?

I have a refractometer and I use it in places where I’m happy with a ballpark number, such as when making a starter or at end of the boil. The graduation marks are so close together that I don’t trust myself to read it accurately.


Triple scale hydrometers all read 1.004. Precision hydrometers are spot on 1.000.

The 4-point difference could just mean they are calibrated for different temperatures, although I thought they were all calibrated for 60F. If you have good tap water it should be close enough, but you are supposed to check calibration using distilled water.

All of mine are calibrated to 60. My sample was 64, which is close enough. It doesn’t matter whether you use distilled or tap for a hydrometer, but it does matter for a refractometer. So says my father-in-law who has a doctorate in chemistry and teaches at the college level. Distilled or not, I would expect all correctly calibrated hydrometers to read the same in the same sample.

Sounds like you have a highly knowledgeable family member. I would seek out their advice rather than some keyboard jockey on the internet. :wink:

I’m not really seeking advice on this one. I’m just being a keyboard jockey. :wink:

I should clarify. When actually “calibrating” a hydrometer (e.g., when making a hydrometer or testing the unit with the intent to correct its performance so it reads 0 in water), you do want to use distilled water. For our purposes, it is perfectly fine to use the same water you use for brewing (assuming your water is actually suitable for brewing). In fact, I would argue that it makes the most sense to test your hydrometer using your brewing water .

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