Checking SG with hot wort

I did my 1st all grain yesterday and ran into a couple of problems.

I brewed a low gravity beer with a small grain bill, Northern Brewer AK47 Pale Mild. It uses ~5.5lbs grain and then a pound of sugar at the end of boil.

I fly sparged in a 10gal cooler (which seems to be too little grain for this size cooler, but that's another post...). I wanted to test the SG of the runnings with my hydrometer, so that I wouldn't go under 1.010. The problem is the wort was just too hot, I placed it in the freezer for a while, but it took too much time to cool. By the time the sample cooled, about 7 minutes, I noticed I would be well under 1.010, which I was about ~ 1.005.

Is there a better way to do this?

I read on here a couple of times that people recommend mixing the sample with 50% very cold R/O water, adjust the reading for the sample temperature and then multiplying the result by two. I like this idea, the only issue I see is that it will increase your margin of error on the reading by 2X. I think anything under a 50% wort sample would increase the margin of error too much and not give you a close enough reading (i.e. 1/3 wort 2/3 H2O). What does everybody think about this method?

The other idea would be to purchase a refractometer, but this has mixed reviews on HBT (please don't turn this into a refractometer vs. hydrometer thread), just let me know if this is your vote.

Thanks to all!

I have a section of PVC pipe that is fitted with a hose barb at one end. It is mounted to my brewstand vertically with the hose attachment at the bottom. I put my hydrometer sample tube inside that tube and turn the water on real low. As the water flows out of the top of the PVC pipe it carries away heat, bathing the sample tube in cool water. I keep a thermometer in the sample so I can see when it is done cooling. I'll post a photo next time I go downstairs.

I only take 3 readings on brew day. Last runnings, kettle full, and post boil (og).

Refractometers are 100% the way to go for taking running samples. You can buy temp adjusting ones... but it really doesn't matter. A tiny drop of hot wort will almost instantly cool once it hits the refractometer.

It's how we did it when I worked at a local brewery for a summer.

You could also consider batch sparging. I only batch sparge (fly is a PITA, in my humble opinion) and I get efficiencies of 75-80% every time. Then you don't really have to worry about running readings. Also there a few people at my LHBS that swear to have never had tannin off-flavors from sparging with too much water... and these aren't old-time homebrewers but guys who keep up with new technologies and trends. Not trying to start a debate, but this is another one of those gray-areas in the homebrewing world.

duckredbeard said:

I keep a thermometer in the sample so I can see when it is done cooling. I'll post a photo next time I go downstairs.

Click to expand...

Thanks. Sounds interesting i look forward to seeing it.

Can't get photo to upload from phone.

Here it is.

Refractometer is the clear choice.. Easy, fast, and accurate for pre-fermentation readings. Hydrometers are still superior for post-ferm measurements.

You can mix equal parts hot wort and cold water, double your resulting gravity measurement and adjust for whatever temp your watered-down sample is at.