Unexpected Starting Gravity (!?)

[JonBrew]

Ok so I just finished my brew day. I had drafted up my beer on Brewer's Friend. Projected numbers as follows:

Batch size: 11.5 L
Boil size: 17L approx.
Boil gravity: 1.044
Starting gravity: 1.066

So I hit my boil gravity bang on. I then boiled down but disaster struck. When I was transferring the wort from the kettle to the fermenter I spilled some. Not a huge about but enough to make a hell of a mess of my kitchen floor.

Judging by the scale on my fermenter I was able to collect 10L. So I figure, assuming I had boiled down to 11.5L, this means I lost 1.5L. However, on taking my starting gravity reading to my surprise I am at 1.056. I therefore assume that I didn't boil down enough so go back to Brewers Friend to rework my numbers.

It's suggesting that, with the same boil gravity of 1.044, to then hit 1.056 SG, I would need to have boiled down to only 13.5L. This then suggests that I spilled 3.5L but I know that cant be right cause there's no way I spilled 3.5 L; that would have flooded my kitchen floor.

Can anyone suggest why I've missed my SG by such a large margin. I know that not actually knowing how much I spilled makes it tricky to determine, but any input would be appreciated. Am I missing something really obvious?

Thanks

 

[johngaltsmotor]

Are you sure of your 17L boil size? You could be right on with your pre-boil gravity, but if you have your volume wrong then your starting total sugar content would be off.

 

[WildGingerBrewing]

AG or extract? If it's AG it could be that your boil gravity is off due to the runnings not being mixed thoroughly. If it's extract, it's almost impossible to miss your numbers, so I would agree that your quantity readings are off. My guess is that your boil gravity is incorrect.

 

[JonBrew]

Thanks for your reply.

I'm not certain of my exact boil size but it wouldn't have been more than a litre either way. Again, judging by Brewer Friend, varying the boil size by that much is not enough to account for the SG difference. Or am I not picking you up correctly?

 

[JonBrew]

AG or extract? If it's AG it could be that your boil gravity is off due to the runnings not being mixed thoroughly. If it's extract, it's almost impossible to miss your numbers, so I would agree that your quantity readings are off. My guess is that your boil gravity is incorrect.

Thanks for your reply. All grain BIAB my friend.

 

[johngaltsmotor]

Thanks for your reply.

I'm not certain of my exact boil size but it wouldn't have been more than a litre either way. Again, judging by Brewer Friend, varying the boil size by that much is not enough to account for the SG difference. Or am I not picking you up correctly?

If you started with 16L instead of 17, then instead of 13.5L you'd be closer to 12.5L to get 1.056, suggesting you would only need to dump 2.5L instead of 3.5 (still a considerable amount more than you think you did).

 

[JonBrew]

Ok guys, with your help, I think I've figured it out. If I don't know for certain what my boil size was, then I cant be certain of my efficiency. I think it's been a combination of a lower boil size (say maybe 15L) and an efficiency of only 60% as opposed to 70% - that would still give me the boil gravity of 1.044 and an original gravity of 1.057. I'm guessing this is what's happened. Sound reasonable?

 

[peterj]

And if you measured your boil volume hot and your final fermenter volume cold (which I assume is probably the case) then you will probably have about 0.5 L in shrinkage due to the temperature difference.

 

[rmyurick]

Yeah, Jon, that sounds reasonable. My first thought was that you didn't have 17l. to start; second, maybe an inaccurate measurement. (did you correct for temperature?)

 

[JonBrew]

yes. recalibrated my hydrometer readings appropriately.

 

[acidrain]

yes. recalibrated my hydrometer readings appropriately.

Does that mean you took a gravity reading hot, and adjusted from there? That will most certainly throw you off since hydrometers just are not accurate above 80 or 90 degrees.
Also, are you sure you got all your wort mixed well before taking a reading?