newb questions concerning mashing and gravity

[perfecxion]

I just made my 2nd AG batch ever, a double ipa. As i was draining the wort from the tun it was initially 1.072 and was supposed to be 1.07 so i was pretty happy, but after 5.5 gallons i noticed it looked pretty clear and when measured it was 1.03. The overall pre boil gravity came out at 1.055. Because the OG was low i just stopped draining there, and ended up with only 5.5gallon in the boil. So after all the loss from boil and hop/trub i only had 4gallon in the fermentor.

My mash temp was at 144-145 for the duration of sacch time and was supposed to be 151. My mash out never got over 165, so overall my temps were close, but still a bit shy of what they should have been.

I kept trying to add warm water during mash to get the temp up, and failed to get it temp to 151 but just ended up filling the tun with water. There was 16lb grain, 4.5gallon strike water, and by the end of mashout the 10gallon cooler was almost completely full of water.

The recipe called for ".75lb corn sugar (0 min late addition)" would this have increased my gravity? Should i have measured after the boil due to this? Or should i always measure post boil gravity? Was my mess up with temp/water volumes likely to blame for my low gravity? Or was it likely something else?

 

[reinstone]

The sugar you added will increase the gravity a little. Did you still add the same hop schedule? It will be ok.

 

[perfecxion]

ya everything else seemed to go fine. i double pitched and its been fermenting for about 48hours. the expected abv was around 9, wtih a lower OG should i expect it to come in at a lower abv now?

 

[djfriesen]

ya everything else seemed to go fine. i double pitched and its been fermenting for about 48hours. the expected abv was around 9, wtih a lower OG should i expect it to come in at a lower abv now?

Depends on what your postboil gravity was. That, or we need preboil gravity and volume, and postboil volume.

taking a quick look at your numbers, you should end up with a really similar ABV, but with a smaller volume.

 

[perfecxion]

any ideas why the gravity changed so much towards the end of draining the wort, is this common? i was supposed to get more like 6.5 gallons of wort at 1.07. Was it a problem that my tun was completely full of water during first runnings of wort?

Im also not understanding how the volume is relevant to gravity/abv measurements.

thanks

 

[acidrain]

I'm guessing you're confusing your numbers.
First, adding all that water didn't help. You ended up with sugars left behind in the grain. The goal (with batch sparging) is to mash with about 1/2 of the total water, drain that, sparge with 1/4 of the water, drain that, then sparge the rest until you have your pre-boil volume.
The 1.07 OG is after boiling, so...
You have to know your boil off rate, so you can collect just enough wort (with all the sugars possible) so that after it boils down, you hit your batch volume and the gravity.
You would have taken your specific gravity readings after the boil, and after any sugar additions, and with the sample cooled to room temperature.

Mash efficiency is volume and gravity pre-boil. This measure how well you extracted sugar.
Brew house efficiency is volume and gravity going into the fermenter. This is also your OG.
Your recipe will tell you what your OG should be. In this case 1.07.