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View Full Version : OG reading WAY off of expected value



CDKeth
03-19-2011, 09:51 PM
I mixed up my first batch of must today and I got an OG reading way outside of what I would have expected. I have used a hydrometer before so I know I'm not reading it incorrectly.

My recipe put 15# of honey in 5G and my OG reading was 1.106.

I realized that I aerated the must before taking a sample to measure OG. Is this probably the cause o the abnormally low OG reading?

I was doing this all with a friend and his nearly-identical recipe came up with an OG of 1.116, which is more what I would expect.

akueck
03-19-2011, 09:58 PM
Could be several things: incomplete mixing, bubbles clinging to the hydrometer, variable sugar content in honey, inaccurate volume/weight measurements...

Bottom line, if you believe your must was completely mixed and there weren't any bubbles lifting the hydrometer (spin to dislodge the bubbles) then I'd trust your reading.

mmclean
03-19-2011, 10:23 PM
Hi CDKeth,

Welcome to GOTMEAD?

The mead calculator is calling out for 1.108 at 79.6 % sugar content. What were you expecting?

tweak'e
03-19-2011, 10:49 PM
Could be several things: incomplete mixing, bubbles clinging to the hydrometer, variable sugar content in honey, inaccurate volume/weight measurements...

Bottom line, if you believe your must was completely mixed and there weren't any bubbles lifting the hydrometer (spin to dislodge the bubbles) then I'd trust your reading.

+1

no one measures water exactly, or honey, theres normally honey sticking to the container.
you got 1.106 and your mate got 1.116, thats not exactly way out.

funny how recipes always call for nice round amounts ;) .the weights are only approximate, rounded to the nearest nice number. always better to fine tune the OG using the hydrometer.

CDKeth
03-19-2011, 11:25 PM
I was expecting it to read heavier. I'm referring to "The Compleat Meadmaker" as I go and was surprised this was out o the range he was telling readers to expect.

I so heavily aerated the must (again, I did that before taking a sample to read the OG) that there probably were bubble on the hydrometer I didn't get off. It was so aerated that it looked cloudy for quite a while.

CDKeth
03-19-2011, 11:47 PM
I reread the OG after it sat for a few hours since aeration and got 1.108

I guess the aeration affected the reading less than I thought. It is pretty light honey.

brewdoctor
03-21-2011, 12:04 PM
Unless you boiled the must and /or the h2o the oxygen would not have been removed. So, I'm sure areating helps but don't see where it would effect sg that much.
As far as the sg, I would check your measuments and see that the exact same amount of h2o was used by you and your friend. Also, I would check the weight of the honey an make sure that was the same as well. One last thing, check you hydrometer. I found two of mine to be off by almost .1.

Hope this helps,
Brewdoctor;)

Medsen Fey
03-21-2011, 12:21 PM
1.106-1.108 is exactly what I would expect with 3 pounds of honey per gallon. That is also what the mead calculator comes up with, so I suspect your readings are correct. Your friend's readings seem a bit high, but it is quite easy to have a little more honey and a little less water than you thought.

wayneb
03-21-2011, 12:27 PM
CDKeth, using the nominal value of 1.417 as the specific gravity of honey (that is true for honey with 18% water content - typical for most commercial honeys), you then mixed 15 lbs (which is 1.271 gallons) into a total 5 gallon batch of must.

You can calculate the value of the initial gravity of your mixture, using the following formula:

S1*V1 + S2*V2 = St*Vt, where
S1 is the specific gravity of your first liquid (in this case, let's call it honey)
V1 is the volume of that addition (1.271 gallons)
S2 is the sp grav of the second liquid (water)
V2 is the volume of that addition (5.000 - 1.271 = 3.729 gallons)

So,
(1.417 x 1.271) + (1.000 x 3.729) = St x 5.00, or,
St = 1.106


Seems to me that your first reading was perfectly on, and the fact that your second reading is slightly higher (1.108 ) simply shows that your honey may have been slightly denser that typical store-bought, having slightly less water content, and you may not have had the honey fully dissolved at the time that you took the reading, or as you guessed, you might have had a couple of bubbles adhered to the glass. I see no error in your measurement technique, and your numbers are right in line with what I'd expect to see as the initial SG for this recipe.

My guess is that your friend's "nearly identical" recipe may not have been as identical as you both had thought.