Things that affect Hydrometer readings

In trying to troubleshoot an issue I *may* be having with my hydrometer (see below) I have run into the following issues brewers have encountered with hydrometer readings:

* bubbles may push the hydrometer higher in the tube/thief, solve by waiting a minute before reading the hydrometer;

* temperature matters, adjust gravity reading for temps significantly higher/lower than 60F;

* taking a reading at the top, not the bottom, of the meniscus;

I would like to suggest that different parts of the carboy *may* have different sugar levels. Is that true? I have seen some here indicate that the corn sugar and water mixture added when bottling often falls to the bottom of the bottling bucket and results in less equal distribution of sugars as a result. I have no idea whether this is true or not.

This question arises b/c I took a gravity reading of my wort yesterday after the cool down (adjusted reading of 1.042) and then one day afterwards before adding yeast or anything else (adjusted reading of 1.050.) This is a HUGE difference and I don't know how to account for it. Suggestions other than those posted here are welcome!

I assume this is a full volume boil?

The convention is to read at the bottom of the meniscus, but in reality so long as you are doing the same thing each time it probably doesn't matter.

Wort/DME/sugar/crap dried on to the bulb of the hydro has thrown mine a long way off before!

MalFet said:

I assume this is a full volume boil?

The convention is to read at the bottom of the meniscus, but in reality so long as you are doing the same thing each time it probably doesn't matter.

Click to expand...

Yes, full volume boil.

And the hydrometer is brand spanking new -- no crud on it yet! Actually, it broke later in the day so now it IS crud.

All sorts of things can effect a hydrometer reading... some can have quite a noticeable effect.. others, not so much...


If the wort is not thoroughly blended, the sample pulled for testing will not be representitive of the entire batch.

Temperature equilibration... allow enough time for the temperature of the tube, hydrometer and wort to stabilize before reading.

If the thief or test jar has residual water or sanitizer in it, it can dilute the sample and give a false low reading. Give the tube and hydrometer a quick rinse with a small portion of wort prior to pulling your test sample.

Suspended solids in the sample can effect the boyancy of the hydrometer. If a cloudy, murky sample is tested, filtered, then re-tested... there can be a noticeable difference in the reading depending on the amount of suspended solids and the density of the solids themselves.

Be sure the hydrometer is free-floating in the wort, i.e not 'stuck' to the sidewalls of the thief/tube.


there are probly plenty more...