Efficiency Woes

[DoblePartiGyle]

Lately I've been getting pretty good boil gravities - in the neighborhood of 75-80% efficient. The weird part is that my OGs consistently come out to about 65% efficiency, so it seems that my initial measurements must be off, and that my efficiency really is still not good.

I use the points/lb system in How to Brew, and the values therein for calculating 100% efficiency. I then take a sample of my wort after all of it has been collected and mixed, and let it sit to make sure it's room temperature for 30 minutes to an hour. I measure my gravity, then multiply by the number of gallons to get the total number of points in my wort, I then divide by 5 to get what the gravity should be based on that number of points in a 5 gallon batch.

I currently mash using 5.2 in a ceramic steel pot that I insulate with a sleeping bag, then do a mashout to 170, and transfer to Listermann's Phil's lauter tun and fly sparge sparge with 170-175F water.

Any thoughts will be appreciated!

 

[grahamfw]

How long does it take you to sparge (and how big a batch)?

Edit: I see 5 gallons. Disregard the size.

 

[ericm]

I'm a little confused by your description - you're saying you're getting 75-80% efficiency-into-kettle (pre-boil?) and ~65% efficiency into fermentor?

to accurately calculate efficiency you need to measure actual volumes, not just use 5 gallons because you're doing a 5 gallon batch. (ie, measure the gravity and volume of your pre-boil wort, and then use the points/lb calculations you're using to calculate your efficiency-into-kettle, etc.)