Gravity Question

[BrewerJoe]

Okay, so today was my first attempt at an all grain brew.

After mashing 8.5 lbs. of two row pale malt and 8 oz. of 120L crystal malt I yielded 6.0 gallons of wort which showed a gravity of 1.032. This reading was taken while the wort was still 150 degrees. Does temp. have an impact on the gravity reading using a hydrometer? If not, I attribute the low reading (poor efficiency) to my el-cheapo mash tun (48 quart ice chest with stainless washing machine hose braid) or maybe my thermometer isn't accurate.

In any event, since I thought my pre-boil gravity was low, I added 8 oz. of DME during my hour long boil. At the end of the boil and cooled to 70 degrees, the gravity ended up being 1.058. So .032 seemed lower than I was expecting and .058 is higher than I expected. Thus I now wonder if taking a gravity reading while the wort was 150 degrees may have been the problem and maybe my gravity was actually higher than 1.032??

So someone please help the newbie understand what was going on!

 

[feenaughty]

the wort needs to be at 60 to a true gav. reading.the hydrometer comes charts that will get you a close to the gav. at warmer temps but will be farther off the true gav. the warmer the wort is.I think you may want to wait to add DME till after you boil and cool a glass of it to check gav. :rockin: let us now how you beer turns out:cross:
Tom F

 

[shawman]

http://hbd.org/cgi-bin/recipator/recipator/hydrometer.html?13310317

when entered in this you had a gravity of 1.051

 

[Frodo]

The temp correction charts can be very imprecise over about 90F. Always cool to at most 90F then correct the hydometer reading. Best to cool all the way to the calibration temp, usually 60F. That's why for all grain it's best to get a refractometer, even a cheapo from Hong Kong for $20.

 

[BrewerJoe]

http://hbd.org/cgi-bin/recipator/recipator/hydrometer.html?13310317

when entered in this you had a gravity of 1.051

Okay, that sounds a little better, but probably high.. I doubt I really achieved 90% efficiency with my set up. Oh well, I guess it'll probably still turn out okay.. I hope..

I'll have to check into a Hong Kong special I guess..

 

[Petho]

I have the exact same sitch. I measured my gravity before pictching the yeast. Is the OG suposed to be taked before the boil? I measured after the boil when the wort was cooled and just before I put it in the fermenter. My temp when I took the reading was 68*.
My first All Grain brew day went well excepting this mistake.

 

[Northcalais40]

When I'm brewing I keep a shallow dish of ice water on the counter. I can take a cup of wort at any temp, put it in a small mixing bowl and swirl it around in the ice water. This cools from 200F to 60F in about 10 seconds. A thin metal pie pan (disposable aluminum) works even faster. Any guess work about temp conversions are eliminated.

 

[Frodo]

I have the exact same sitch. I measured my gravity before pictching the yeast. Is the OG suposed to be taked before the boil? I measured after the boil when the wort was cooled and just before I put it in the fermenter. My temp when I took the reading was 68*.
My first All Grain brew day went well excepting this mistake.

You don't "need" to take the preboil SG, but you can in order to determine if you are over or under on the sugar you got from the grain (extract and lauter efficiencies). You need to know the volume too, subtracting 4% for wort expansion at boiling temp vs 70F.