Measuring LME

My calculation shows a result of 1.048, which is still a little short. Did you add any specialty malts? They do add a few points.

LME: (36.8 x 6)/5.5 = 40.15
DME: (45.0 x 1)/5.5 = 8.18
40.15 + 8.18 = 48.33 Therefore 1.048

Plus specialty grains (1 - 2 pounds could easily give you the missing gravity).

 

My best guess is you ended up with less volume than you expected.

I've seen my LHBS fill LME and they stop at 6lbs. That hot water thing is pretty much standard practice and I'm sure other LME people know you'll do that.

Oh, also DME adds more gravity per unit weight, did you account for that in your calcs?

 

I should mention that there is a range of potential gravities for both LME and DME depending on the manufacturer:

LME: 1.034 - 1.038
DME: 1.040 - 1.045

Thus, depending on the extracts you used, the specific gravity of the wort (assuming using only 6 pounds of LME and 1 pound of DME), could range from 1.044 - 1.050. Different calculators use different assumptions regarding the potential gravities of the two extracts. The better ones should either provide a range, or allow you to enter (or change) the assumed potential gravities of the two extracts.

 

How exactly did you measure the wort volume. Was trub a part of this volume?

Cheers!

 

3-4 points seems like it could be a combination of hydrometer error, measurement error, mixing/dilution error, volume error, batch to batch variation in LME concentration, and minor ruptures in the space time continuum. Nothing to sweat over. If you are convinced it is none of these possibilities, perhaps you suffer from overconfidence.

 

Actually, it's more like 5 points, which is fairly significant. Not only that, I find the difference intriguing, since, in addition to brewing, I for one, am fascinated with the math behind brewing, and have written - and use - all my own formulas for all aspects of brewing. I do have BeerSmith but rarely use it since the math itself is so much fun for me, and using the formulas allows me to have a better insight in what's actually happening while brewing. It's a bit like being excited about detective work.

So even while I agree that there's little to worry about in terms of the final product, it's still educational for some to try to figure out why there's such a difference. Knowing these things helps all of us improve our understanding of the brewing process and allow us to keep improving our beers. Otherwise we would still be making the same crappy beers from 1.5 Kg. Muntona and other can kits that were common during the early nineties.

 

And the answer to: "Was trub a part of this volume?"

Cheers!

 

That is a fair bit of hyperbole. Being 'off' on the OG by a few points (whether it be 5 points or 3-4 points) is nothing like what you are stating here.

Cheers!

 

No, there's certainly a huge gap. But I was referring to all the minor and major improvements over the years leading to the excellent homebrewing knowledge, equipment and ingredients we have today. Every little bit along the way has led to this.

 

I can easily shrug my shoulders at your 5 points. Our measurement devices are imperfect, and people make mistakes in measurement, and your calculations do not appear to account for these things. Sorry, @CarolusP, but your assertion that you were being extra careful despite being low on sleep would not hold up in court. "Yes, your honor, I had been drinking, but that is precisely why I was being extra careful!"

 

I'm with you, Carolus. it's easy to shrug off all errors, but only by looking more deeply into and studying errors do we progress in our knowledge and understanding of the process.

A range for the error has already been established, yet the error is still 5 points outside of that range. If it had been within that range, the error could easily have been shrugged off. The calculation is simple and there are very few variables, unlike mashing. Thus, logically, there must be something else that we are yet missing. Most of the errors in measurement that could have caused this much variation have been reasonably ruled out, and it's hard to believe that the potential gravity of either the LME or DME would fall that far outside of the range commonly accounted for.

So, the only variable that I can think of that has not yet been addressed is the temperature of the wort when you measured the volume. Water expands when heated, so if you measured the 5.5 gallon volume when hot, you would not have an accurate measure of the volume. It would actually be less than 5.5 gallons when cooled to room temperature, driving up the SG. Do you know what the temperature of the wort was when you measured the volume on your stir stick?

 

Um, does it? I've never had my water expand before, unless I turned it into ice or vapor.

 

Have you never heard of thermal expansion? See:

https://en.wikipedia.org/wiki/Thermal_expansion

Or:

http://www.engineeringtoolbox.com/volumetric-temperature-expansion-d_315.html

I guarantee that the volume of your wort expands as it is heated.

 

Right, I guess I never noticed because of the negligible change on the volumes I use. I suppose it could make a difference in a 5 gallon batch.