How to adjust pre-boil gravity for temperature

[caseyodell]

I start to heat my wort after the first batch sparge to increase my time efficiency. By the time I have my full batch for boiling, the temperature is up around 190 degrees. How do I get an accurate pre-boil gravity reading at that temperature?

 

[arnobg]

I usually take a sample and let it cool in the fridge/freezer and take a hydrometer reading once it is close to 60F. I think most people just use a refractometer.

 

[WrQth]

I usually take a sample and let it cool in the fridge/freezer and take a hydrometer reading once it is close to 60F. I think most people just use a refractometer.

I second the use of a refractometer since it only takes a couple minutes for the sample to come down to the calibrated temp to give an accurate reading. Always be sure to verify calibration of your refractometer.

 

[eric19312]

I'm also refractometer guy. I use it as a check that my recipe is going pretty much on track and accept "close enough". I do get a hydrometer reading on my wort going into the fermentor.

 

[caseyodell]

Great answers. thanks for the help

 

[wilserbrewer]

I set my wort sample in the freezer for 10 minutes or so, a good tip I read is to have a large ceramic mug in the freezer already, then use that to chill the sample.

I should probably get a refractometer, but I'm a minimalist.

 

[specharka]

Uhh...I just measure it with a hydrometer. Usually take a sample of wort around 135 -140F, when my sparge is done, and use a hydrometer temperature correction to get the true value.

Hasn't failed yet.

 

[m1k3]

refractometer is great... but make sure it is calibrated! mine is off almost every time by a few points. (leaving it in the sun will throw it off)

 

[RussPDX]

If you use your hydrometer too hot you can melt the wax plug in it which can throw it off. Refractometers are great and I use one hot side, but you can also put some wort in a cocktail shaker and swirl in a bowl of ice water for very speedy chilling. About 1-2 minutes. My stick thermometer fits right in the holes strainer holes of the shaker it is really easy, just don't burn you hand on the shaker at the beginning.

Also if you are using this to see if you are on your numbers make sure you take the expansion of the liquid at the high temp into account in your volume calc. On my 10 gal setup I typically collect 12.5 gallons at boil but to figure my gravity I calculate at 12 gallons. There is roughly a 4% increase in volume at boil.

 

[specharka]

If you use your hydrometer too hot you can melt the wax plug in it which can throw it off. Refractometers are great and I use one hot side, but you can also put some wort in a cocktail shaker and swirl in a bowl of ice water for very speedy chilling. About 1-2 minutes. My stick thermometer fits right in the holes strainer holes of the shaker it is really easy, just don't burn you hand on the shaker at the beginning.

Also if you are using this to see if you are on your numbers make sure you take the expansion of the liquid at the high temp into account in your volume calc. On my 10 gal setup I typically collect 12.5 gallons at boil but to figure my gravity I calculate at 12 gallons. There is roughly a 4% increase in volume at boil.

This makes no sense. It's a self-contained object with a fixed mass and buoyancy. It's not going to un-calibrate itself by being exposed to high temperatures.

 

[RussPDX]

Maybe mine was off from the beginning as I did not calibrate it before hand. I did however use a hydrometer in hot wort over and over again. The wax plug (or wax like substance as I am making the assumption it is wax) melted enough the shift. The little beads inside started to move around. I was concerned and tested by making a known solution. Weighing everything for accuracy. The hydrometer tested off and was discarded.