Checking a hydrometer

[bamnq6]

G'morning-

Anyone noticed a difference in hydrometer readings between StarSan and water? After I pull a sample and get a Gravity, I just fill the test cylinder with StarSan and plunk the hydrometer back in for a double check and a quick clean....

It wasn't until this morning that I though... Maybe that's a dumb idea?

ipe:

Opinions??

 

[ColoHox]

Hydrometers are calibrated to read 1.000 in a sample of water at a specified temperature. As Starsan is not water, I would expect a different value, in fact I think it is about 1.32.

 

[Wynne-R]

StarSan solution is at .15% so it’s mostly water. I tried to calculate the density, but there were too many variables I didn’t know. Based on phosphoric acid at 1.88 g/mL and the other 50% being about 1, I guessed it at 1.0008.

So I got crazy and measured a sample with a precision hydrometer, right at 1.001. So if you’re worried about contamination from StarSan residue, wrecking your sample, relax. For what it’s worth, my tapwater is also 1.001.

So, unless you dry the cylinder, you will very slightly dilute the sample. Of course you can rinse it with beer, but who wants to do that? At any rate the error will be much too small to measure by any normal means.