Best Method to get Pre-Boil Gravity

[ontum]

What is the best method to get a pre-boil gravity reading?

The reason I ask, is because I get readings with my refractometer that vary. I heat my wort up to 208° while I am sparging, so my pre-boil wort is already hot when I need that measurement.

Yesterday I brewed 10 gallons of a Blonde Ale, and used two methods to try and get pre-boil gravity. My final gravity was 1.046 at 11.2 gallons.

Method 1
I stirred the wort really well, took about a 8 oz sample from the whirlpool port. I let the sample cool down for 30 minutes, and then dipped my refractometer into the wort and measured at 1.048. With 12.85 gallons of wort, Beersmith states my mash efficiency at 98.1%. This cannot be right. When I pull a sample into a container, I can see lots of grain particulate in the wort. So, when I took the sample I tried not to disturb the grain at the bottom of the container, but still had extremely high gravity.

Method 2
I stirred the wort really well, removed my paddle and dripped a couple drops on the refractometer. I let it sit for a minute for the temperature to cool and measured 1.040 with 12.85 gallons of wort. Beersmith tells me that this is 81.7% mash efficiency.

I have experienced having irregular and inconsistent pre-boil gravity readings previously, but just measure several times until I find some king of pattern or consistency.

 

[Oginme]

I use a mason jar with a cover that has a hole for a thermometer drilled in it. I mix well and pull out about 300 ml of combined wort, cover and put into a SS bowl with cold water. Once it has cooled a bit, I add ice to bring it down to room temperature. I then take a hydrometer and refractometer reading before adding the wort back into the boil kettle.

Generally, this takes about 10 to 15 minutes, during which the kettle is heating up to a boil.

I do the same thing at the end of the boil (having sanitized the mason jar) for final readings. I use the wort cooled here to get my yeast going again since I prepare my starters a couple of days ahead of time and have decanted as much of the starter wort as possible.

Anywhere else in the process, I use the refractometer to get readings. The pre-boil and post-boil dual readings help to maintain calibration.

 

[atom]

Denny recommends this: (from experimental homebrewing)

 

[Qhrumphf]

I use a pipette, grab a few drops in there, and then run the bulb of the pipette under cold tap water. It cools from mash/boiling temp to room temp in seconds. I do something similar to the Denny suggestion above to cool my mash pH samples though.

 

[Qhrumphf]

Also, your method #2 was mathematically accurate based on your post-boil volume and gravity. My guess is that your first sample re-stratified in the 30 mins it was cooling.

 

[dwhite60]

I just bought a refractometer. Hated waiting for the hydrometer
sample to cool.

I pull 1/4 teaspoon of wort and place it on a ceramic plate.
Cools to room temperature in 5 minutes. Take a couple drops
and put on refractometer.

Stir well before taking your sample.

All the Best,
D. White

 

[Natdavis777]

I pull both pre-boil and post-boil samples from the BK. Once the batch starts to boil, I pull my first sample. This ensures me that everything is nice and evenly distributed. Same as the post-boil. I'll pull that sample right before I kill the heat. Cool both samples down and read with the refract. This has been the most accurate way I've tested

 

[Qhrumphf]

I pull both pre-boil and post-boil samples from the BK. Once the batch starts to boil, I pull my first sample. This ensures me that everything is nice and evenly distributed. Same as the post-boil. I'll pull that sample right before I kill the heat. Cool both samples down and read with the refract. This has been the most accurate way I've tested

That's not a bad way of doing it. Only reason why I don't is that I want to be able to adjust before the boil even starts if need be (which I almost never need to do, unless I'm doing my once-every-couple-years 1.100+ batch where I'm usually a few points under). Trying to account for adjusted boiloff, adjust gravity, or adjust hopping when the boil has already started is fighting against myself a little to much for my taste.

 

[stpug]

My final [original] gravity was 1.046 at 11.2 gallons.

Method 2
I stirred the wort really well, removed my paddle and dripped a couple drops on the refractometer. I let it sit for a minute for the temperature to cool and measured 1.040 with 12.85 gallons of wort. Beersmith tells me that this is 81.7% mash efficiency.

(1.040 x 12.85 gallons) / 11.2 gallons = 1.04589 or 1.046

Your second method worked much better.