OG keeps coming in little low?

[av8er79]

I'm still in training. Brewed about 5-6 extract batches with specialty grains. The last couple batches my initial OG reading has been about .005 off. The recipe I boiled yesterday called for an OG of 1.072 and I ended up with 1.066.

-What causes this? Could it simply be that I do not have exactly 5 gal of water?
-You take the OG reading after transferring to fermenting bucket and topping off with water correct?

 

[pelipen]

Lots of things:
1. Not completely mixed
2. Hydrometer reads wrong. Check in pure water
3. Hydrometer readings are not at correct temp
4. Measurements are off
5. Quantities are off (ingredients)

 

[av8er79]

I thought there might be a lot of variables. AS long as I am pretty close, it should not be much of a concern right?

 

[RUNningonbrew]

I am an all grain brewer but technically the OG should be the same before and after you add the water... Because gravity is measuring the amount of sugar in solution ad is not relate to volume, so If all the other factors are correct above then you can just boil longer...someone please correct me if I'm wrong.

 

[Pezman1]

If you are brewing extract kit, use all the ingredients, and end up with the correct amount of wort, you will be in range of the target OG.

Keep in mind that the target OG is just that, a target. Some kits will even give you a target range (Like OG 1.055-1.060)

All the numbers you stated are just fine.

Pelipen gave a nice list of the things that can give you false readings. One of them in particular is a hazard in doing partial boils with top-offs. It is hard to get partail boils and top-off water to mix perfectly, which can give false lows or highs.

Another culprit is getting ALL the LME out of the bottle. I finish up by pouring hot water into the LME jug, putting the cap back on, and shaking untill all the LME is dissolved, pouring it into the boil kettle.

Pez.

 

[pelipen]

I am an all grain brewer but technically the OG should be the same before and after you add the water... Because gravity is measuring the amount of sugar in solution ad is not relate to volume, so If all the other factors are correct above then you can just boil longer...someone please correct me if I'm wrong.

Not quite. Specific gravity will change by volume, but the "points" won't. This is what allows you to predict gravity changes by adding lme/dme or water.

For example 1.050 in 1 gallon, will be 1.025 if you top off with an additional gallon of pure water.
50 * 1 / 2 = 25.

 

[Maddoghoek]

If you top off a partial boil, you have to stir alot to get it 100% mixed. Also remember hydrometer readings are going to be slightly off depending on temperature. The instructions that came with it should explain how to correct for temp.

 

[HibsMax]

I'm still in training. Brewed about 5-6 extract batches with specialty grains. The last couple batches my initial OG reading has been about .005 off. The recipe I boiled yesterday called for an OG of 1.072 and I ended up with 1.066.

-What causes this? Could it simply be that I do not have exactly 5 gal of water?
-You take the OG reading after transferring to fermenting bucket and topping off with water correct?

With extract kits you should hit the numbers bang on. In theory. . But as already mentioned above, there are factors which could affect your readings. I always stir the $@&)) out of my wort (I use an electric drill and a plastic mash paddle for a couple of minutes) and adjust the reading for temperature. I think that my initial / early batch readings were a little off because I wasn't mixing my wort as rigorously as necessary.

 

[Pezman1]

Another thing to keep in mind.

If you are brewing an extract kit, there is no reason whatsoever to take an OG at all. Really! One less thing to do, worry about, sanitize, etc......


Pez.


EDIT FOR CORRECTION - As pointed out by helibrewer, this should read "brewing a PARTIAL BOIL" extract kit!

 

[helibrewer]

I do full boils so when doing extract I monitor gravity to stop the boil at the right time...I don't top off unless I don't catch the boil off correctly.

 

[Pezman1]

I do full boils so when doing extract I monitor gravity to stop the boil at the right time...I don't top off unless I don't catch the boil off correctly.

OK. you got me.
Even then, once you know your boil off rate your should be able to come pretty close to five gallons in a 60 minute boil. Yeah, I know... just being argumentative...

Cheers!

EDIT - I edited my above statement to read "partail boil extract kit"

 

[Revvy]

Attention new brewers, yes your original gravity reading is wrong. Don't panic.