I think I've been an idiot

[BorderReiver]

So I think I've been an idiot.

I've been cooling my wort after boil by use of simple convection in the fermentor, prior to pitching yeast, as I do not have a wort chiller. The last three batches I've noticed that my OG readings were quite a bit lower than what they should be. I put it down to my mashing kit losing heat and therefore efficiency, and was trying to see how to boost said efficiency. Nothing was working.

For my last batch I think I may have hit on the reason for my lower than expected OG readings - taking the reading before the wort has cooled.

I believe this is the cause of my readings because the reading I took of the most recent batch of beer the reading I took two days after fermentation started (it was a taffelbier, so low-alcohol) was higher than the OG reading I got off the uncooked wort. And then I remembered high school chemistry, when I was taught that hotter liquids would be less dense than cooler ones.

Has anyone else had a similar experience?

 

[W0GWT]

Right you are! I think I used to have a sheet that adjusted for temperature. If you google it, I bet you'll find it!

 

[jekeane]

Hydrometers are calibrated for 68° F well mine is... You will need to do math or use an online calculator to adjust. http://www.brewersfriend.com/hydrometer-temp/

 

[passedpawn]

Play around with this. You'll see. BTW, most hydrometers are calibrated in the factory at 60 or 68F (mine's at 60F). Look closely at yours, there might be an indication on it somewhere. It will be useful for the calculator.

http://www.brewersfriend.com/hydrometer-temp/

 

[BorderReiver]

Thanks for the links. Those will definitely allow me to correct my record sheets.

 

[Greyhound]

So I think I've been an idiot.

Well, I think "idiot" is a little harsh. We all have to learn somehow and none of us will ever know it all.

 

[ThinBrewLine]

In the end, how did it drink?

If it was good, no worries!
Have another!

 

[bknifefight]

What kind of temperature are you talking about? Even at 100*, your measured SG will only be 4 points lower than actual. Sure, this may be part of your issue you but had said:

I've noticed that my OG readings were quite a bit lower than what they should be.

"Quite a bit" is more than what I would attribute to a hydrometer misreading, unless you are checking it at a ridiculous temperature.

 

[LandoLincoln]

Here's a good brewing experiment...

Get a wort sample and take a hydro reading of it every ten minutes as it cools. Record the SG and the current temperature. Use the online brewing compensation calculators to compensate for the degree difference and see how accurate the brewing compensation calculators are as the wort cools down to the temperature that the wort is supposed to be for a correct reading.

My friend and I did this test and we found out that the brewing compensation calculator that we used was pretty useless for temps above 120°, but lower than that and it was pretty accurate.

 

[BorderReiver]

I had done my readings with the Unchilled wort (pretty much straight from the boil pots), so yeah, I checked it at a ridiculous temperature.....