Original Gravity Question

[Fritz61]

I expect this question has been addressed in other threads, but I hope someone can answer this perplexing question. It has happened to me several times - but not every time.

I made a partial mash IPA yesterday. The malt bill was 10.7 lbs (including 6 lbs of light DME and .5 lbs of Dextrose). I mashed the remaining 4.2 lbs of grains for 60 minutes at 150 degrees. I batch sparged the finished mash with about 2 to 2.5 gallons of 170 degree water to end up with a 3.5 gallon boil.

Upon finishing the boil and topping off to 5 gallons, the OG was a mere 1.043 versus the anticipated 1.058. This seems impossible considering the 6.5 lbs of DME and Dextrose alone - per the calculators - should produce an OG of about 1.054 for an anticipated ABV of 5.10%.

I suspect it has to do with the mash efficiency - but I only mash in order to add specific flavor characteristics to my beers.
Thanks for any suggestions.

 

[Nosybear]

I suspect it has to do with topping off. Did you stir or otherwise mix the wort before taking your gravity reading? It can't be the mash efficiency! The wort you measured was 11 points less than if you'd used the extract alone! You either have a stratification problem (wort wasn't mixed well) or a problem with the hydrometer (not calibrated, broken, wrong temperature measurement).

 

[Fritz61]

I suspect it has to do with topping off. Did you stir or otherwise mix the wort before taking your gravity reading? It can't be the mash efficiency! The wort you measured was 11 points less than if you'd used the extract alone! You either have a stratification problem (wort wasn't mixed well) or a problem with the hydrometer (not calibrated, broken, wrong temperature measurement).

Thanks for the quick response. I did not stir the wort after topping it off. I thought the agitation while adding the extra water would stir it up sufficiently. I'll make sure to do that next time and hopefully that will be the difference. The beers always taste great and seem to have more oomph than a 3.7 ABV. Cheers.

 

[J A]

Post a link your recipe (be sure you make it public, searchable). Something is off from the start.

 

[sbaclimber]

Thanks for the quick response. I did not stir the wort after topping it off. I thought the agitation while adding the extra water would stir it up sufficiently. I'll make sure to do that next time and hopefully that will be the difference. The beers always taste great and seem to have more oomph than a 3.7 ABV. Cheers.

I think Nosybear is probably correct. I had the same problem, just with the opposite effect. My OG was waaaaaaaaay high, and turns out, it was just a lack of stirring. I also assumed the bit of splashing around would be enough, but it definitely wasn't.