sareinhart
Well-Known Member
I'm confused about pre-boil gravity vs. OG. I think I must be doing something wrong with my math. Here's the particulars. I have a 10 gallon beverage cooler mash tun. I always pre-heat it with hot tap water to minimize temperature loss during the mash. Mash thickness 1.25 qts/lb. Mash temp started about 151 and ended about 149. I mashed for an hour. Lauter took 42 minutes. I collected 8.9 quarts. Sparge water temp 148 - made up the rest of my boil volume. Total sparge time was 1 hr 8 mins.
5 lbs Pilsner Malt
5 lbs Munich Malt
1 lb Dark Munich
.5 lbs Caramunich
(as per Northern Brewer's Octoberfest recepie)
Preboil gravity - RAW reading 1.025 (if I recall correctly, that reading was taken at 112F - although I didn't record it.)
Preboil gravity - Corrected for temp 1.042
I collected 6.9 gallons of wort.
That gave me a bad brewhouse efficiency - about 67%. I've been running much better - about 75% on other batches.
Boiled for 90 minutes and got almost exactly 5 gallons of wort. After chilling I got an OG of 1.069. The northern brewer recipe says that expected OG is 1.058.
Here's what I don't get - how can my brewhouse efficiency be so poor and yet I still overshoot my OG by so much? Does it make sense that I could have a pre-boil gravity of 1.042 - boil off about 2 gallons and wind up with an OG of 1.069?
5 lbs Pilsner Malt
5 lbs Munich Malt
1 lb Dark Munich
.5 lbs Caramunich
(as per Northern Brewer's Octoberfest recepie)
Preboil gravity - RAW reading 1.025 (if I recall correctly, that reading was taken at 112F - although I didn't record it.)
Preboil gravity - Corrected for temp 1.042
I collected 6.9 gallons of wort.
That gave me a bad brewhouse efficiency - about 67%. I've been running much better - about 75% on other batches.
Boiled for 90 minutes and got almost exactly 5 gallons of wort. After chilling I got an OG of 1.069. The northern brewer recipe says that expected OG is 1.058.
Here's what I don't get - how can my brewhouse efficiency be so poor and yet I still overshoot my OG by so much? Does it make sense that I could have a pre-boil gravity of 1.042 - boil off about 2 gallons and wind up with an OG of 1.069?