help!! consistently low OG

[megDC]

i started all-grain brewing 3 weeks ago and brewed 3 times. all three batches have had low OG. i am using a refractometer for measuring.

yesterday i brewed a pale ale, was going for 1.045 and got 1.037
last week i brewed a belgium dubbel, was going for 1.060 and got 1.055
3 weeks ago i brewed a gose, was going for 1.048 and got 1.042

do you think my refractometer needs calibrated or somewhere in my process is off?

thanks

[brewinhard]

How do you brew? Batch sparge, fly sparge? When are you taking your reading with the refractometer. Do you have an ATC (automatic temp. conversion) refractometer? How is the crush of your grains? Is your thermometer calibrated correctly? Have you tried taking a cooled hydrometer reading (60 F) and comparing it to the refractometer's measurement?

Any extra info would be great here so we can provide some assistance.

[dmtaylor]

The two absolute biggest hitters are:

1) The crush. If you're not sure if you've been crushing enough, then crush it twice. Your efficiency will probably shoot up by 10 points overnight.

2) Volume measurements. Need to be as accurate as humanly possible. If you were supposed to end up with 5.0 gallons but actually ended up with 5.4 gallons or 5.6 gallons or something else, your efficiency will be WAY off.

Make sure you're following those two things, and your efficiency will skyrocket. There are other possible effects, but none as huge as those two. Well, okay, I suppose there is a third item, but it should be a no-brainer:

3) Good to the last drop. If you didn't get all your wort out of the mash tun, your efficiency will be impacted. If you are a batch sparger, the first runnings is more important than the sparge. Get it all out. You could see an increase of ~5% from doing this.

Okay, now that's all I'm going to say for now.

[megDC]

i fly sparge. it usually takes me an hour.

i take the gravity reading right before i pitch. yes i have a ATC refractometer. i did compare refractometer and hydrometer readings on the gose, and it was the same.

i have a monster brewing MM-2 mill. i left the gap in the mill where it was set when i got it, 0.045". i think the crush is good, i only crush it once.

i have not calibrated thermometer in a year or two, so i could check that.

i have a glass level gauge in my kettles, so i think i am pretty good with knowing my volume. i am going to make a volume measuring stick to be on the safe side too.

[maxwell]

The gauges and marks that come on kettles cannot be trusted. You need to calibrate it using for instance a half gallon measuring cup or a gallon jug that you've calibrated by weight. My first kettle was off by 1/2 gal by the time it was full to the 28 qt mark.

Max

[Spiderbrewer]

Hey. I'm new at this all grain too but a couple of possibilities. Check your gravity before your boil. Thats the beauty of a refract. The wort cools almost instantly and you can just boil off until you get to your pre boil number. Also I would definitely calibrate your thermometer and refract. If your temp is too high or low your conversion will be off but if your refract is off everything else is pointless.

Good luck.

[BarefootLion]

Other thing before you go and adjust shit that might be right....
Adjust your efficiency
Try for a lower efficiency see if you can hit that number, like 65%...I'm just assuming you are going for 70-75% and coming up short.

Yes the answer may lie in other peoples posts but maybe you just aren't that efficient..its ok, we won't laugh you your small efficiency in the shower.

[megDC]

I have been assuming my efficiency is 70%. So lets say, I assume my efficiency is 65%, to keep my OG the same, I have to increase the grain and keep everything else the same? How do I actually find my true efficiency?