What would cause the OG to be so low?

[dmbnpj]

Brewed an all grain today. My girlfriend found the recipe here (Not tonight HONEY im tired ale):

TastyBrew.com | Recipes

Everything went great as far as quantities and temperatures (only our 2nd time doing an all grain) but when we measured the ABV and OG with our hydrometer after pitching the yeast it was only at 2.75% and 1.025? What would cause this to be so low?

**One change to the recipe I had to make was to use Wyeast 1056 American yeast instead of White Labs California Ale because my local brew shop only carries Wyeast.

**Also, the plastic tube that the hydrometer comes in was cracked in our situation. So, I just floated the hydrometer in the 5 gallon bucket of wort (hope this doesnt skew the reading?)

 

[SavageSteve]

Since it's all-grain, then there can only be two reasons for a low OG: poor efficiency in extracting sugars from the malt, and a larger wort volume than planned on. I'm assuming you boiled down to your target volume and didn't top off with any water, which would be the most likely reason for a low OG if you did that.

Of course, a bad hydrometer or reading could also be the culprit-- have you calibrated it lately? Did you correct for the sample temperature?

-Steve

 

[dmbnpj]

Actually this was an all grain boil that I do outside with 3 converted kegs (keggles). So its a full boil.

 

[Vuarra]

What was your OG like on your first All-Grain, and did you change any aspect of how you mashed it?

 

[dmbnpj]

Since it's all-grain, then there can only be two reasons for a low OG: poor efficiency in extracting sugars from the malt, and a larger wort volume than planned on. I'm assuming you boiled down to your target volume and didn't top off with any water, which would be the most likely reason for a low OG if you did that.

Of course, a bad hydrometer or reading could also be the culprit-- have you calibrated it lately? Did you correct for the sample temperature?

-Steve

You could be right about the larger wort volume than planned on. I have a little over 5 gallons collected so maybe thats why the reading is off. I started the boil with 7 gallons and it boiled down to a little over 5 which is what I ended up with.

How do you calibrate a floating hydrometer?

 

[SavageSteve]

How do you calibrate a floating hydrometer?

Test it in plain water to see if it reads 1.000. Then, test it in a solution with a known specific gravity-- mix up some DME or LME in some water-- and see if the hydrometer reading matches the predicted specific gravity.

In both cases, try to get the sample temperature to be the same as the temperature to which the hydrometer is calibrated.

-Steve

 

[ajf]

Just a thought, but did you make a yeast starter?
If you did, and you used a turkey baster to take the hydrometer sample, you could have taken the gravity of the starter rather than the wort.

-a.

 

[VTBrewer]

I know this doesn't help now, but in the future you may want to take a reading preboil. There are calculators (google Brewhouse Efficiency calculator or click the link in my signature) that will let you know where you're at prior to the boil. If you keep some DME on hand you can adjust it. 1lb of DME will bring you up about .009.

I invested in a refractometer (about $50 on ebay and worth its wait in gold) to take preboil readings of just a drop or two of wort, and it automatically adjusts for temp.

Until I dialed in my AG process it was not unusual for me to reach for that 1/2 lb or lb of DME after mash out.

 

[dmbnpj]

Back to the poor efficiency point you had....it brings up another question I have about the sparge. I do a batch sparge. I use about 1.5 quarts of water per pound of grain in the mash tun. After that sits an hour, I drain that wort into the boil keggle. Then, I use the sparge water (which has been heated to 175 degrees) and pour that into the mash tun. I dont measure the amount of water here I just make sure I have about 6.5-7 gallons worth added in with the grain. Then, I let that sit in the mash tun for about 15 minutes. I then add that wort from the tun into the boil keggle (which already has a little bit of water in it from the initial mash). I usually try to get about 7 gallons of wort in the boil keggle preboil due to the evaporation. Is this a proper way to batch sparge?

 

[SavageSteve]

That's a fine way to batch sparge-- I used that technique on my last brew-- but with only one sparge, I get about 70% efficiency. Another sparge and it goes up to 80%.

I notice that the recipe you used doesn't indicate what efficiency they are assuming, so that's probably the biggest source of error right there. You should use some brewing software so you can calculate what efficiency you'll need, or, how much extra/less grain you'll need to use based on your efficiency to hit the recipe's OG.

You should definitely take a pre-boil gravity reading so you know if you're on track to hitting your target OG after the boil. You'll also be able to track your efficiency so you can adjust recipes to fit your process.

-Steve

 

[Donner]

Not to introduce another element into this, but the crush of the grains does impact your all grain results. DId you crush the grains yourself or go to some place new?

A poor crush will mean fewer sugars will be extracted.

 

[ajf]

When you add your mash water do you stir really well? With batch sparging, it is the stirring that dissolves a lot of the sugars. You may also want to check the temperature of the sparge. Ideally, it should be 168 - 170F. If cooler, it has been my experience that efficiency drops a bit.

-a.

Edit. I meant when you add your sparge water, not mash water. For mashing, stirring enough to break up the dough balls is fine.

sorry.

 

[dmbnpj]

I didnt know about stirring really well. I basically just stir to break up any doughing but other than that Ive always just done a quick stir because I didnt want to lose too much heat. I will try that differently next time. As far as the temperature I mashed at about 154 degrees and then added in the 175 degrees sparge water for the sparge.

 

[Bobby_M]

The stirring is also really important when you put the sparge water in. Other than that, it could be your crush.

 

[coryforsenate]

Probably low efficiency from your mash.

 

[blackwaterbrewer]

+1 on the double batch sparge. also, i have found that i need my mash-out and sparge water to be more like 190 F to reach a mashout temp of 170. also, a painfully slow run-off will do wonders for you efficiency. your spigot should never be opened more than 1/2 way during any of the runoffs. your sparge should take at least 45 minutes or you are doing it too fast.

 

[dmbnpj]

By double batch sparge do you mean basically just use a few gallons on the first sparge and then a few more gallons for a second sparge?

And good point on the sparge taking 45 minutes by not opening the spigot more than 1/2 way. That is another mistake I make. I use a march 809 pump and when I drained it I had it freeflowing. Oops.

 

[Bobby_M]

I don't believe in slowing the draining of a batch sparge. If you've converted in the mash properly, slowing the sparge down (in batch sparging specifically) should yield no better efficiency. If it does, it would only be attributed to additional conversion during the sparge.

 

[GlassblowersBrew]

Can using 2 oz whole hops during the boil affect the OG post boil?

 

[davesrose]

Hops, no matter what state they're in, don't contribute to gravity readings. Gravity readings can contribute to hop utilization though....

 

[GlassblowersBrew]

Hops, no matter what state they're in, don't contribute to gravity readings. Gravity readings can contribute to hop utilization though....

Interesting... I had a low OG post boil on my first all grain batch too. Was supposed to be 1.075 but I hit 1.045. My LHBS suggested that it could have been the whole hops sucking up the sugar, so I figured it must have been that. I will have to reevaluate my process and try to get better efficiency in my mash/sparge techniques. Im sure I just did something to fast or a little off. I just added 3 lbs of DME to up my gravity and just moved on with the process. Oh well.

 

[dmbnpj]

I don't believe in slowing the draining of a batch sparge. If you've converted in the mash properly, slowing the sparge down (in batch sparging specifically) should yield no better efficiency. If it does, it would only be attributed to additional conversion during the sparge.

By "converted in the mash properly", do you mean using the proper amount of water (1.5 quarts of water per pound of grain), hitting target temp. (about 154 degrees) for about an hour?

And how long should the sparge water sit in the grains after the mash if doing a full batch sparge?

 

[Bobby_M]

You would expect a mash to fully convert in 60 minutes given the thickness and temps you've noted but it also depends on mash pH and grain bill. Bills that have a lot of unmalted adjuncts might take 90 minutes, etc. The only way to check for sure is an iodine test.

 

[dmbnpj]

Iodine test, wow haven't heard of that one yet. I have found that brewing really coincides with keeping reef fish tanks. I had a saltwater fish tank for several years and I am seeing a lot of similarities. I wish I kept my refractometer but I do still have my iodine that I used for the fish tank (brand new though, never used). Off to the wiki on iodine. Thanks.

 

[broadbill]

Interesting... I had a low OG post boil on my first all grain batch too. Was supposed to be 1.075 but I hit 1.045. My LHBS suggested that it could have been the whole hops sucking up the sugar, so I figured it must have been that. I will have to reevaluate my process and try to get better efficiency in my mash/sparge techniques. Im sure I just did something to fast or a little off. I just added 3 lbs of DME to up my gravity and just moved on with the process. Oh well.

What your LHBS told you is BS....whole hops would absorp higher amounts of liquid, not just the sugar in that liquid. Although whole hops would may wreak havoc with your volume measurements, they will not screw up your gravity readings by sucking up sugar.

The obvious culprit in these low OG situations is the crush....the crush that was probably done by the LHBS that gave you that bogus information. Sounds like they were trying to cover their a** for their shi*ty crush. Also sounds like they KNOW they have a shi*ty crush, because it sells more grain.