Lower OG after boil??

[megavites]

So I brewed a Belgium pale ale today,
Doughed in and hit my target temp (152) for 60 min. Mashed out using slightly higher temps to get grain bed to 170, check. Now, my notes say
1.040 @135=1.055. I check 3 times and got within a point of that number.
After boil I ended up with 1.052??

The only thing I can think of is that I measued the OG before I got to
full volume, ie it was diluted further. But I'm sure I took a sample just before boil and corrected for temp to get my OG. Not sure what happened here. I'm confident of my calibrated digital thermo, so that's not it.

In the end it, the SG was to be 1.053 so It's right where I wanted it but just trying to figure out what happened. (BTW, I was not drinking today)

 

[ajf]

Temperature compensation at 135F is not very accurate.
Did you take the pre-boil sample from the bottom of the kettle without stirring? That could explain things as the wort in the kettle will be denser at the bottom than the top.

-a.

 

[Brett0424]

Also, you didn't say what your preboil and fermentation volumes were. If you added ice or water to dilute and ended with a higher volume of course your OG would be lower. I'm assuming this isn't the case though and agree with above post, your first reading probably wasn't that accurate.

 

[WBC]

There is no way that sugar disappears. There is a measuring mistake.
Water boils off so it gets thicker. 1.040 can become 1.050. If you then add water it does become thinner or less OG.

 

[megavites]

Temperature compensation at 135F is not very accurate.
Did you take the pre-boil sample from the bottom of the kettle without stirring? That could explain things as the wort in the kettle will be denser at the bottom than the top.

-a.

This is probably the case. The wort wasn't stirred and all three samples
were from the bottom outlet valve. I do use Beersmith for temp compensation
and it appears pretty accurate as the sample cools, maybe within a point or two.

I'll stir next time.

 

[zoebisch01]

Yeah, those two things are probable causes. Stratification of the sugar layers, stir really well. Temperature conversion is a non linear scale and the higher you go the more accurate you have to be on the measurements in both temperature and sp gravity, what is off by one point at high temp represents a much larger difference then when you are off at the calibration temp of the Hydrometer. You should take hot measurements with a grain of salt. One cool (no pun intended) idea I gleaned from a member is to place a pan (I use one of my SS fry pans) and stick it in the freezer. Pour your sample into there to cool rapidly, you can just put it back into the boil after you measure.

 

[megavites]

Ok, I'm really confused now.
Brewed a Hefe last night and measured gravity before the boil, after strirring the boil kettle real good. Took three readings of the same sample at different temperatures, all were the same. (1.041)
Expected 1.053 after the boil and measured 1.041 again??

Thought maybe the hydrometer was bad and bought a new one today, did a comparison check and they both read the same. Two digital thermos read within 2 deg. of each other, and one of them is calibrated, so I'm at a loss as to why, after boiling off 3/4 to 1 gal, my gravity reading was the same.

Thoughts?

 

[WBC]

This will help. During your brewing when you take a sample you must stir well and scoop out your sample (Do not drain samples from a ball valve unless well purged) and save it in the fermentation refrigerator because that is close to 65F. Put all the samples in the same refrigerator. When you are all done brewing you can read your samples more accurately because they are at the right temperature and you have rested a while and can devote your full attention to getting good readings. Accuracy depends on accurate volumes of water as well as ingrediants too. No guessing allowed.

 

[megavites]

Damm, I guess I'm going to have to brew another batch test this out.