Checking SG pre boil

[Pyg]

I don't know If this is possible, but it also meet occurred to me.
Does anyone check the SG pre boil?
Can a hydrometer be used in 160F .
I have always waited until after mash, after boil, after cool down and checked SG prior to pitch in yeast.

Is there a danger of the hydrometer cracking in the moderate heat?
Or have I simply been over looking this obvious step?

 

[Stillraining]

I check all my "running's" and both "pre" and "post" boils at around 125 to 140 degrees. That's always my first quick check just to verify things and what the temp falls to just putting the wort into the vial and waiting a couple min....never had an issue with the hydrometer.
I have checked at 170+ before with no issues so go for it...but that was a long time ago when I read post boil right away...Now I don't get worked up about post boil and wait to take reading after I'm all chilled and yeast is pitched by that time its down to 120 or lower as well..... I know almost exactly what it will be anyway from my pre-boil number and boil off rate...so it is what it is so to speak....and if I'm off .001 or .002 who cares..Its Beer!

As mentioned in another thread I have 3 hydrometer vials so I leave all my samples separate and in-tack so I can take reading again at lower temps ( maybe slightly more accurate) and/or if I forgot to write them down the first time.

Here a first running's measuring 072 at 126 degrees is corrected for temp to a 084 with a 60 degree calibrated hydrometer.

 

[bucketnative]

Your hydrometer will not be accurate at 160F. I cool the pre-boil sample in a pitcher of ice water in my freezer until it reaches the appropriate temperature. Then I measure it. Takes a few minutes. I also do the same for my post-boil gravity.

 

[Oginme]

Yes, always. I have a designated mason jar equipped with a metal cap which has a hole drilled for a thermometer. I take a sample of pre-boil wort in the mason jar and place it in an ice bath. Within 5 to 10 minutes it is at 60F, where my hydrometer is calibrated, and I can pour the chilled wort into my graduated cylinder and take a reading. Meanwhile the wort is coming up to boil.

I highly recommend getting the wort as close to the calibration temperature of your hydrometer. Anytime you try to take a reading at a temperature significantly higher than ambient, the correction is questionable since the sample is continuing to cool as you are trying to take a reading.

 

[kh54s10]

I measure first runnings, after the first sparge and preboil. The first two are just for the record. I use a temperature correcting refractometer. It takes just seconds for the reading to stabilize.

 

[Stillraining]

Next brew I will record and photograph all the readings for accuracy comparisons from various hot "corrected" temps to 60 degree calibrated temps We will Myth bust the "Not accurate" statements and we will see if that is true or untrue. Should be interesting and good for all of us to know.

 

[eric19312]

Always measure pre boil gravity. You should know what to expect when you plan your recipe. Then when you have the pre boil gravity you can make a course correction to get your your intended original gravity.

Beer Alchemy shows it like this on my brew day instructions sheet:
Gravity Before Boil: 1.060 SG (15.3 Brix)
Original Gravity: 1.070 SG (17.7 Brix)
Final Gravity: 1.014 SG (9.4 Brix)

Volume Before Boil: 13.50 US gals
Volume After Boil: 12.50 US gals
Volume Transferred: 10.50 US gals
Water Added To Dilute: 0.0 qts
Volume At Pitching: 10.50 US gals
Volume Of Finished Beer: 10.00 US gals

Total Water Required: 16.77 US gals
Total Grain: 27lb 4oz

These are all expected values

If I hit my volume right (and I fly sparge so that is a given if I don't get distracted and over collect) and Gravity Before Boil is low I know I undershot expected efficiency. I then have a variety of ways to get to planned OG. Usually what I would do is collect another 0.5 or 1 gallon and then boil longer. I'd start my 60 minute timer when kettle volume reached the original planned 13.5 gallons. To boil 14.5 gallons in a 15.5 gallon pot calls for fermcap but works out fine. Other options would be to boil longer/harder without sparging extra. I could check an evaporation calculator and see what volume I need to get to hit the intended pre boil gravity.

As for how to do it I use a refractometer for pre boil gravity. That is easy and the cheap ones seem to work quite well. It is nice that Beer Alchemy shows me expected gravity in SG and Brix units since refactometer reads brix.

If using hydrometer the ice bath methods described above are fine. If collecting a hydrometer sample I'd add the sample back into the boil kettle during the boil. No point in dumping it unless you are like @Stillraining and want to keep full hydrometer bottles standing around during brew day. Accident waiting to happen I think

I do get a hydrometer sample for original gravity using the chilled wort. I collect this during transfer to the fermentors. I can actually get what I need from my pump lines. I don't add the post boil post chill wort back to the fermentors. That is a pre ferment sample to taste.

 

[mattdee1]

I used to measure pre-boil gravity when I first started brewing, to convince myself that my mash was happening as planned, but after a half dozen or so brews with predictable results, I just stopped doing it. Eventually, I just deleted that field from the spreadsheet template that I use to record brew day info.

I don’t know, I guess it never hurts to have data, but for my purposes that particular measurement became useless after I realized that I am able to successfully mash grains. Ultimately I decided that the pulling of the sample, chilling it, measuring the temperature, and recording it was a series of steps that, however simple, I could remove in the interest of cutting some “busy work” out of my brew day. Like somebody said earlier, beer will happen whether I know that data point or not; besides, I have a good enough handle on my boil off rate that I could probably estimate pre-boil gravity with more than acceptable accuracy in the unlikely event that I found myself giving a ****.

 

[Stillraining]

mashesuote=eric19312;7557466]
No point in dumping it unless you are like @Stillraining and want to keep full hydrometer bottles standing around during brew day. Accident waiting to happen I think

Ah my good sir..But I do return my first 3 samples back to the boil pot eventually.. I'm only risking a mess for a short while..

And its usually just me in my brew sphere, so very little risk of that. I got into the habit because I'm notorious for not so much forgetting to note down a reading here or there although that happens, but for labeling it as to what it was. The old brain is getting foggy. Especially when I have two batches going at the same time.

 

[charliehorse]

I don't take a pre-boil reading... mostly because it's where it should be (or at least where I expect it) most of the time but I do take a sample glass of first runnings and at a shot of bourbon to it and enjoy that during the sparge. It'll warm your soul on the coldest of days.

 

[thereverendmaynard]

I always check pre boil and then adjust for temp/volume to ensure I will be close to my post boil OG target. I have a good idea of boil off, so I am able to get very close on my targets. This gives you the option of adding sugar/DME/LME to increase gravity in case you miss your target.

 

[Stillraining]

Woops! I just realized I posted my findings to the wrong thread!...

https://www.homebrewtalk.com/showthread.php?p=7563720#post7563720

PS: Eric19312... if you look closely you can see a small spill just for you...