Trouble Reaching My OG (Pre-Boil Was OK)

[JorgeGautier]

Last week I brewed an Arrogant Bastard clone. My pre-boil gravity was off by .001 so I was pretty happy with that... But my OG (post-boil) was off by .009! I thought that because my pre-boil gravity was so close to the original (estimated), my OG will result as well in a closer number to the estimated OG.

My boil was vigorous and I boiled for 90 min (as the recipe stated) so I have no idea what could have interfered in reaching my estimated OG.

PS. My gravity measurements were taken at the same temp.

 

[progmac]

the obvious answer is that your boil off was less than calculated. however, if this wasn't the case, consider when you measure your "pre-boil" gravity. until the boil starts there may be some stratification between the first and second runnings; so it is possible to draw a sample that does not reflect the actual gravity of the batch.

 

[wilserbrewer]

It would be of value to measure volume as you progress.

You likely have a boil off volume set to high for your system.

You can consider just boiling longer to reach your post boil volume. If you do opt to extend the boil, the "late" addition hops should just be timed to flame out.

I typically boil to a finish volume rather than a precisely timed boil, w/ late hops timed to the anticipated finish, rather than a precise overall boil time.


Wilserbrewer
Http://biabbags.webs.com/

 

[JorgeGautier]

Good to know that! Next time I'll boil to reach volume instead of time and see how it goes. Thanks

 

[Gameface]

You could also boil to your OG. Whatever your priority, gravity or volume.

 

[pvault98]

It took me a few brews to get familiar with my new system when I built it, but now I hit my numbers dead on. In order to get me to this point, I took measurements every 30 mins and recorded my boil off rate and gravity at each 30 min interval. After reviewing my notes I now know that I boil off 1.5 gallons per hour and this translates to a .013 increase in gravity. If I reach/adjust my preboil gravity based on my planned boil time, I always come in right on target.

 

[JorgeGautier]

That's great advice pvault98. I'll try to calibrate my equipment that way and see how it goes.


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