Best Way To Take Pre Boil Gravity?

[chadjaja]

A while ago I put too hot a wort into my hydro tube and melted the sucker.

So at the moment I sparge into a cube, elevate the cube and rack it into the boiler via hose. I then give the lot a slow stir to make sure all the runnings mix and give me a consistent gravity. Then take the temp, stick the hydro into the wort whilst in the boiler and work out the calibrated gravity.

BUT im having problems with the pre boil gravities. Today I put the hydro into the boiler after the stir, took the temp and it was 1020 at 69 degrees. That would give me a gravity of 1040 pre boil. Just about spot on as I was wanting a pre boil of 1041 according to beersmith.

My boil off today was 8L's and just checking my gravity post boil and cooled I get 1042 :blink:

This has happens a few times and its damn frustrating. After all it throws out my hop amounts, IBU's and final alc %.

Does having the hydro floating in the boiler rather than the skinny testing tube create any problems or make a difference? I've got a new heavy duty hydro tube that takes hotter temps but I assumed that putting it in the boiler would be just as good. Surely after racking where it slightly whirlpools and then stirring all the runnings are mixed thoroughly enough to give an accurate gravity reading? Or so I thought :blink: :angry:

Any advice?

 

[seemax]

I take a sample from the kettle after I finish sparging when all the wort is under 70C .. no problems with melting the standard hydro tube...

 

[Cocko]

Rig depending:

How I do it is, after the final spaging to the kettle, as in kettle is at pre-boil volume, I take from the kettle tap enough wort for a sample into one of those stainless milk jugs you get with a home/domestic style coffee machine. I then let it sit for the rest of the brew day and by the end of the brew and clean up - take a temp reading on the sample, usually about 20-28 depending, and pour it into the hydrometer tube and take a reading.

The software I use, Brew Alchemy, allows you to adjust reading temp and Hydrometer calibration temp so sorted, obviously SG is effected by temp and needs to be calculated to the temp your hydrometer is calibrated at.... would be 20* at a guess...

In essence, get a sample amount of wort out and let it cool, you don't have to use your hydrometer at pre-boil temps!

Hopefully some help.

Cheers

 

[manticle]

What I do when I remember to take preboil is just scoop a jug into the kettle pre-boil but once all the runnings are in there. Take out 200-500 mL, let it sit. It will cool reasonably quickly.

Measure it when it's a bit closer to cooler, calibrate as necessary then gently add it back to the boil.

 

[felten]

I take an airtight container, dip it into the pot for a sample and then seal it up and throw it into the freezer, it gets down to room temp pretty quickly. I read somewhere about evaporation on such small samples can possibly throw the gravity reading out, can't hurt to cover it up.

 

[bignath]

I use a refractometer for everything. I also use my hydro at pitching yeast for my OG and then it goes back into the bag o tricks until fermentation is done, where it gets used to cross reference my refractometer at FG.

Refract's are fantastic once you work out how to use 'em, quicker than a hydro, can be used at any time throughout the brewday, and uses less wort to do it...

I love my refractometer.

 

[Cocko]

I read somewhere about evaporation on such small samples can possibly throw the gravity reading out, can't hurt to cover it up.

Really? Makes sense I guess but to what degree?

I only take PB Gravity because the software I use needs it to give me an efficiency reading - which also makes sense, as the gravity reading from the mash is efficiency and post boils is an unpredictable non constant due to boil vigour varies, even on the same rig....

Why else would PB gravity be important enough to question half a point or 2

 

[itguy1953]

Buy yourself a refractometer. This was the best $50 I ever spent on brewing gear. You can continually pull wort samples and test the SG regardless of the temp if you get a temperature compensating one.

I use it to check SG before and through the boil to see if I need to extend the boil or add more water. I also check the SG of the sparge runnings to test if I have pulled out most of the sugars. I normally stop the fly sparge at 1010.

 

[Rotgut]

I take an airtight container, dip it into the pot for a sample and then seal it up and throw it into the freezer, it gets down to room temp pretty quickly. I read somewhere about evaporation on such small samples can possibly throw the gravity reading out, can't hurt to cover it up.

Agree... get the sample as close to 20 deg asap, rather than rely on 60 odd deg adjustments. I stick my pre boil sample in the freezer, only takes 10 minutes to get a good reading.

 

[Cocko]

Doesn't beersmith or similar allow you to edit the temp of sample and hydrometer calibration?

 

[chadjaja]

yup beersmith adjusts it for you based on the correct temp reading of 20 degrees. Also the hydro comes with a paper chart you can use too.

basically I'm being told to let it cool so it seems there is little faith in the ability of the adjustment to be made for temp?

 

[Cocko]

basically I'm being told to let it cool so it seems there is little faith in the ability of the adjustment to be made for temp?

I would say no, more so an agreement that using hot wort and melting stuff is not necessary.... well that how I read it.

Cheers

 

[Hatchy]

I would say no, more so an agreement that using hot wort and melting stuff is not necessary.... well that how I read it.

Cheers

I read it as encouragement to spend $30 on a refractometer from ebay. If I didn't have 1 I really doubt that I'd bother with getting readings while the wort is hot.

 

[Cocko]

I read it as encouragement to spend $30 on a refractometer from ebay. If I didn't have 1 I really doubt that I'd bother with getting readings while the wort is hot.

I think the common consensus here is let the wort cool down... before using your hydrometer, however you do it.

but sure, a refractometer is great but doesn't it have temp restrictions too? Seriously asking, can you put a wort sample in one at 80* ??

 

[bignath]

but sure, a refractometer is great but doesn't it have temp restrictions too? Seriously asking, can you put a wort sample in one at 80* ??

Yeah mate, i do it regularly. Nothing broken with it yet....(emphasis on yet)

Quite often during the boil i will draw out a sample and put it straight on the refractometer, take temp and run it through beersmith just to see how things are going....

 

[Hatchy]

I can't remember if the add said what temps it can be used at, I just assumed that it'd be ok with boiling wort.

 

[manticle]

I think the common consensus here is let the wort cool down... before using your hydrometer, however you do it.

but sure, a refractometer is great but doesn't it have temp restrictions too? Seriously asking, can you put a wort sample in one at 80* ??

As far as I understand the temp restrictions are the same/simialr - it's just that you use a drop as opposed to 200mL so it cools much quicker.

 

[Hatchy]

I just had a look at 1 on ebay & it compensates if the temp is between 10 & 30. I'm not sure if mine came with a book, if it did then I've lost it so I'm not sure if mine is the same. I'll start letting my wort cool to 30 before getting a reading. Thanks for pointing that out Manticle & sorry to anyone I've misinformed.

They're under $30 including delivery buy it now with the stronger dollar.

 

[raven19]

I use a refractometer for everything....

I love my refractometer.

+1

Buy yourself a refractometer. This was the best $50 I ever spent on brewing gear.

+2

A great piece of kit for your brewery for sure.