Partial Mash Efficiency Confusion

[JuGordon]

I recently did my first partial mash, using:

5 LBs Briess Pale Ale Malt
.5LBs Briess Crystal 60
4 LBs Briess Light DME

(Collected 3.7ish Gal of wort)

I wanted to see what efficiency I got out of the mash. So I took a preboil gravity of just the wort that was mashed. I took the gravity reading and got 1.030, which is pretty horrible efficiency (especially with 3.7 gal). I didn't worry too much because I figured that would be the case. RDWHAHB, right?

I eventually added the DME at flameout and after I cooled the wort and added it to my fermenter and topped it off to 5 gallons and aerated it, I took my official OG and got 1.068 (which was my target). This, however, puts me at upwards of 80% efficiency. Did I not get a uniform sample or does the DME add that much efficiency?

Thanks, dudes!

 

[chickypad]

Efficiency doesn't apply to the extract portion - you get what you put in. One of the measurements is wrong or your volume is off. The 3.7 gal of 1.030 wort would mean you yielded 111 gravity pts from your mash. But if you ended up with 5 gallons of 1.068 wort that's 340 pts, minus the approx 176 pts from the DME would be about 164 pts from your mash.

Did you mix the runnings well before measuring? Did you cool the mash sample? Did you mix after topping off - its notoriously hard to get an accurate reading after top off.

 

[JuGordon]

Hmmm... Did I cool the mash sample, oops... You got me, if I temperature correct using approximate temperature of 140F, I get 1.042, which is at 75% efficiency. Well, I now officially feel quite stupid. Thanks, though!

 

[chickypad]

Sounds like the issue. I find that the temp corrections for my hydrometer don't work well over about mid 80's so I either use the refractometer or let it cool.