Hitting expected OG with partial boils + top off?

I've only done four extract brews, and I've only measured the expected original gravity once. The other 3 were too low. The first two I know I didn't thoroughly mix the after topping off leading to a much lower gravity than I expected. However, I can't explain yesterday's brew.

Last night's batch:
American Ale extract kit from morebeer.com:
7lbs Pale LME
1lb Crystal 40L
1 oz Galena 60 minutes
1 oz Cascade 5 minutes
1 oz Cascade 1 minute
1 L WLP001 starter.

Instruction sheet is giving an estimate of 1.053, and Beersmith is giving an estimate of 1.051. I measured 1.042 at 60.5 *F.

Boil was 3 gallons, lost about 0.5 gallons to boil off/grain absorption. Topped off to 5 gallons. Shook vigorously for about 30 - 45 seconds. Used my auto siphon to take a sample.

What did I screw up? How do you guys hit your expected original gravities?

You are either not mixing long/hard enough, reading hydrometer wrong, or it is not calibrated correctly. It is nearly impossible to miss your OG when extract brewing. I'm pretty sure it was higher.

Well, he does have a pound of crystal in there, which could contribute as much as .007 points, but prob more like .005

How are you treating the crystal? I don't buy thos ekits, are the grains already crushed? It could be the size of the crush.

Also, how accurate is your thermometer?

One more thing (and I know this is a little extreme), but had you recently rinsed your siphon, test jar, and hydrometer? I use the thief that lets you take readings in the thief and I usually fill it once, drain it, and refill before taking a reading to make sure there's no dilution of wort.

VTBrewer said:

You are either not mixing long/hard enough, reading hydrometer wrong, or it is not calibrated correctly. It is nearly impossible to miss your OG when extract brewing. I'm pretty sure it was higher.

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Here' a picture of my hydrometer reading. Hard to see how I read that wrong.
It is a relatively new hydrometer. I broke my first one cleaning it.

This same hydrometer was used to take the OG of the beer that I DID measure the expected OG. Doubt it's a problem with it or that it's not calibrated correctly.

This leads be to believe that I didn't shake it long or hard enough...

Grizzlybrew said:

Well, he does have a pound of crystal in there, which could contribute as much as .007 points, but prob more like .005

How are you treating the crystal? I don't buy those kits, are the grains already crushed? It could be the size of the crush.

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I steeped the grains at 155 F for 45 minutes. The Crystal was already crushed.

Grizzlybrew said:

Also, how accurate is your thermometer?

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I think it's pretty accurate. I haven't calibrated it in ice/boiling water. Need to do that.

Grizzlybrew said:

One more thing (and I know this is a little extreme), but had you recently rinsed your siphon, test jar, and hydrometer? I use the thief that lets you take readings in the thief and I usually fill it once, drain it, and refill before taking a reading to make sure there's no dilution of wort.

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I took my auto siphon out of my starsan solution immediately before taking the sample. I filled my hydrometer tube about 1/2 way then put the remainder in a cup. Why? I'm not really sure. I think I needed an extra pair of hands thinking that I was going to tip over the tube. I cleaned up the kitchen and then proceeded to take the reading. I filled the tube up with the remainder from the cup. Then plopped in the dry hydrometer and let it overflow into the sink to get a good look at the hydrometer scale at the very top of the tube.

i have had the same problem doing extrat and partial boils for my last couple of brews. this last one i shook the better bottle around in circles on its edge for 5 minutes to get it to mix well and i was only off by .004. its tough to get it to mix well and get an accurate reading. id guess that is why.

I had the opposite problem this weekend. I was brewing the Magic Hat #9 clone, and after I steeped the grains, I turned the heat up. It set for about 30 minutes but could not reach a rolling boil, then I realized the propane valve was only slightly cracked. I brought it up to boil, and continued. The OG was supposed to be 1.051, and my reading was 1.064. I realized a boiled out over a gallon of water, and I didn't make up the full boil. Therefore I had to add water to get to the 5 gallons, and I got the OG close to 1.054. I hope it still turns out O.K.

thesanch said:

This leads be to believe that I didn't shake it long or hard enough...

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I'd vote for this. You really have to shake long and hard (heh heh) to mix up wort with top-off water. When I did partial boils, I'd usually put a tennis ball under the bucket and bounce steadily and heartily for 3 minutes or so (which is longer than it sounds - your arms should be pretty damn tired by the time you're done). Once I started doing that my OG readings starting coming into line.

The good news is that fermentation mixes everything up anyway, so other than not getting an exact OG reading, there's nothing else to worry about.

Why not just stir in the top off?

Two reasons.

1. It leads to what we're talking about, low OG readings. Wort and top off do not mix well together, and it varies how well depending on the the SG of the wort.

2. You need to aerate your wort anyway, so go nuts.

+1 on not enough time.

I usually have my top off water already in the carboy, then rack onto it. After that, I shake the crap out of the carboy for a good ten minutes - last week I messed up my knee because I was shaking it so hard. Got a good amount of areation too, things were splashing around, and I hit my OG dead on.

Sanch,

Thanks for the specific responses. I guess it is due to improper mixing, which leads me to another suggestion. I'm not sure why I didn't think about this earlier.

Lets say you're OG is supposed 1.053 at 5 gal. This means you have 265[53*5] GU (Gravity Units) total.

Before you add top-off water, take a gravity reading. If you have only 3.75 gal in the carboy, take 265, divide by 3.75 and you will get your intended target. In this case, you would be looking for 1.071 (265 GU/3.75 Gal).

One last suggestion, have you calibrated your hydrometer in pure water at 60 deg? It could be a defect in the hydrometer.

Grizzlybrew,

Sounds like I didn't mix it well enough... oh well.

That is a great suggestion and makes complete sense. I will definitely do that extra calculation on my next extract batch (thinking of attempting a small 2.5 gallon all grain as my next brew -- Yoopers DFH 60 minute IPA clone).

I have not calibrated my hydrometer. I'll do that today when I get home.

Thanks for all the responses!

I went ahead and tested out my hydrometer in ~60*F distilled water.



Looks spot on to me!

Tested out my digital thermometer in boiling water (207*F - where I live) and ice water.



Looks good to me!

I brewed a belgian ale a couple of weeks ago and couldn't figure out why my reading was 1.160 when it should not have been higher then 1.080. Now I know that when I put the thief in to take a sample I got all the concentrated wort from the bottom of the bucket prior to areating. Thanks for the help!

Dammit learned something new today. I have got to stop doing that. Thanks for the tip on mixing wort and top off. Even better, thanks for eq for measuring OG of partial boil wort to figure out top off amount. Knew you could do that in my head just didn't click that I should do it. Oh well.