how to check pre-boil gravity

[log]

If you don't have a refractometer or whatever how do you check pre-boil gravity? Do you take a small portin of the wort, cool it off and then check? I am continually comming up 10-13 points short every brew and trying to narrow down my mistakes. i do have a hydrometer by the way. Thanks

[Evan B]

You can get a refractometer on Ebay for $25. Best investment you'll ever make

[ajdelange]

Refractometers are fine for checking the relative decline in runoff extract as sparging progresses but give, at best an approximation, to the actual extract content of the wort. So yes, the best way to get a pre-boil gravity extract measurement is to cool a sample of the wort and use a good hydrometer. It is best to take the sample shortly after the commencement of the boil as the boil will mix the wort which will have been stratified by the lautering process.

To take a gravity reading from boiling wort I transfer some of the wort to the test cylinder which is standing in a 2 quart stainless steel pitcher (which gets used for many things besides this during the brew day). The pitcher goes under a tap running cold water and in a few minutes the wort is cool enough to get an accurate reading without having to do temperature corrections. Just be sure none of the cooling water splashes into the mouth of the test jar.

[Chupa LaHomebrew]

I just stir the boil kettle well, take a sample for my hydrometer, and take a gravity and temperature reading in the tube. I don't cool it down, it's usually about 130 by the time I check it. I adjust for the temperature with a function in Promash. I have only had 1 problem with a bad reading and it was when I took the sample at just before boiling, so it was about 190+ degrees! That was off and telling me I hit 95% efficiency. But at 130 my hydro works great.

[log]

I'll try and modify my wort cooling process and stick with my hydrometer for now. Unless somebody has a better argument for refractometer. Thanks for the input.

[manwithbeers]

I use my refractometer and it has always been quite accurate. I use a pipet to collect a sample of the wort as soon as the sparge is done and my kettle is filled to the calculated preboil volume. I also fill a pipet from some more wort from the drain in the mash tum to get a reading on my final runnings. I let the pipet samples cool for a couple minutes and then test them. when I get a chance. I don't even worry about mixing them up, they both just get dropped into a coffee cup upside down until I get to them. It's easy to figure out which is which because one is around 3 Brix and the other is usually around 11+ Brix.

I bought my ATC Refractometer on Ebay. When this one breaks I will get another. Best instrument I have bought since I started this years ago.

[tkehijacker]

I had been looking forward to a refractometer for years. I finally broke down and ordered one on Ebay for like 25 or 30 bucks and I've been kicking myself for not getting it 2 and a half years sooner.

[ajdelange]

I use my refractometer and it has always been quite accurate.

I'm not trying to be a wise guy here (though I've been accused, justifiably, of that in the past) but how do you know it's accurate? To make a statement like that you have to be comparing it to something that is of known accuracy and that would have to be a pycnometer (much too much work for most homebrewers), digital density meter (out of the price range of most home and even craft brewers) or precision hydrometers calibrated against density meter or pycnometer.

I have found that the refractometer I use agrees sometimes to within about 0.1°P with precision hydrometers which agree to within about 0.1°P with a digital density meter but at other times the disagreement is closer to 1.0 °P and this is for wort. Once yeast are pitched or cold trub forms or alcohol is produced disagreement goes up appreciably. There are published procedures for the use of refractometers in these cases but they all require calibration for the type of beer being brewed against a digital densitometer or pycnometer.

Refractometers are fine for determining when to terminate collection at lauter and I do use one for that purpose but to get actual meaurement of OG (and runoff final gravity) I use the hydrometers.

All of this turns on how accurate is accurate enough for you. 0.1 °P is certainly accurate enough for me. 1 °P (7.5% error in a 15 °P wort) isn't. The problem is that even though I'm convinced the error is going to be 0.1-0.2 most of the time I don't know when it's going to be 0.9 - 1 (or greater).