Out of Town

I'm going to do some vacationing on the west coast this week. I'll be sure to try to take notes on anything that I have out there. That being said, don't expect much here in the coming week.

Cheers!

Scale Recipes Up/Down

BrewCalc has been updated. It now has a sheet that will scale recipes up/down according to your specifications. The first sheet ('OG, IBUs, ABV%, etc.') is a bit cleaner as well. I've hidden the ugly results of the Tinseth utilization calculations as to cut down on distraction.

I'll probably be updating BrewCalc in the next week or so with some fun new stuff. In particular, I'm working on making the Points per Gallon numbers adjustable by the user without futzing a whole lot with the calculation in J13. I'll post once I get it up and running.

In case you ever wanted to do this backward...

Disclaimer: The proceeding lines will probably only make sense to you if you're familiar with Glenn Tinseth's Hop Utilization formula. This is about to get very geeky.

Where,

O = Oz. of hops
I = IBUs
U = Utilization Factor (Bigness factor*Boil time factor)
G = Gallons of Finished Beer
A = Alpha Acid percentage

(O*A*U*74.9)/G = I

This is not the original formulation that Tinseth provides, but it produces the same numbers regardless.

If you had a target IBU in mind, and wanted to determine what amount you would need to reach it, here's the formula you would use:

I/[(A*U*74.9)/G] = O

Behind the Scenes

Things have, in fact, been going on despite all appearances.

I've been working on a utility for BrewCalc that will enable the user to scale recipes up or down. It will even adjust amounts of your ingredients based upon extract efficiency. I have the grain portion of this sheet worked out, now I'm working on adding the hops portion. Here's how it will work when its finished: The user will enter a recipe that he/she has been given in the first worksheet ('OG, IBUs, ABV%, etc.'). The user will then click on the Scale Up/Down sheet where figures will be calculated based upon batch size, extract efficiency, and new hop utilization figures (as per Tinseth). The end result will be the new amounts for each ingredient listed in the original recipe.


Secondly, I've been putting together some new charts as of late. I've been working on graphing out similar styles on a graph whose Y-axis is Original Gravity and whose X-axis is IBUs. These graphs show ranges of OG/IBUs and even show where the intersections are of similar styles. I only have a few complete thus far, but I'll begin to post them as I continue to work on them.

Lastly, I just took the BJCP exam for the second time last night. It was as long and arduous as I recalled, though I suspect I bettered my score substantially this time around. I'll find out exactly how I fared in the next three to four months. That being said, I'm a little burnt out on technical homebrewing information right now, which means that Tech Tues will have to get pushed back to next week once again. Hope to see you then.

How Much Water Do I Add?

I know that I said I'd be doing the Technical Tuesday column on the impact of Sodium levels in brewing water this week, but I think it's going to get put off again. Instead, I'm going to detail another calculation regarding hitting target original gravity.

In contrast to the previous post about boosting OG by adding DME, this is going to show you how to calculate the amount of water you'll need to decrease OG.

(Note: This method assumes that you have already cooled your wort and are planning on adding water to the fermenter. Of course, you should never fill a bucket or carboy so much that you don't have at least a gallon or two or headspace left for the krausen. Additionally, it is advisable to add the cleanest water possible. This will lessen your chance of infection by bacteria or wild yeast that may be present in your water source. Boiling water and cooling it rapidly is a good method for making sure your top-off water is clean.)

You're almost to the end of your brewday. Your cooled wort is in the fermenter and you're taking a hydrometer reading for your records. Oh horror of horrors, you're ten points high! You know that you can dilute the wort you have to reach your desired OG, but how much water shoul you add?

Here are the numbers that we need at the outset:

1.) Gallons of Wort
2.) Original Gravity in GUs (pre-water addition)
3.) Desired original gravity (in GUs)
4.) Total Gravity Units [Original Gravity (in GUs)*Gallons of Wort]

(A quick word about GUs: You can convert specific gravity to GUs by multiplying OG*1000, then subtracting 1000.)

Let's say you have 5 gallons of 1.060 wort. However, you wanted an OG of 1.050. First find the Total Gravity Units (GUs).

[Original Gravity (in GUs)*Gallons of Wort] - 60*5 = 300.

Here's the calculation you'll use:

[Total Gravity Units/Desired OG (in GUs)] - Gallons of Wort. That's it!

[300/50] - 5
6-5 = 1 Gallon.

You'll require an additional gallon of water in order to bring your gravity down to the desired 1.050.

Here it is one more time with a new set of numbers.

1.) Gallons of Wort = 3
2.) Original Gravity in GUs (pre-water addition) = 77
3.) Desired original gravity (in GUs) = 54
4.) Total Gravity Units [Original Gravity (in GUs)*Gallons of Wort] = 231

[231/54] - 3
4.28 - 3 = 1.28 Gallons.

DME Calculations

If you've ever brewed a batch and come up short on your OG by more than a few points, you may have wanted to fix it by adding some DME. This is a good way to make up for extract that didn't come out of the mash for whatever reason. But before you start weighing out the contents of that spare bag of DME, how will you find out how much you need?

This is really easy. Daniels[1] tells us that we can reasonably expect 45 points per gallon from DME. That means that if we dissolved 1 pound of DME in one gallon of water, we'd have a resulting OG of 1.045. So to make a five galllon batch with this same OG, we'd need five pounds.

Do this first. Divide 45 by the size of your batch in gallons. I typically do five gallon batches, so 45/5 = 9. This number just tells me how many points I can expect to yield when adding 1 pound of DME to a five galllon batch. Makes sense too - add five pounds to five gallons at 9 points per gallon, and it's easy to see why your OG is 1.045.

So if you happen to come up short 9 points, just add one pound. But if you need more or less, what then?

Easy. Divide the number of points you need by the number of points yielded from one pound. That is, if you need 5 points, divide 5/9 = ~0.56 pounds. If you need 11 points, 11/9 = ~1.22 pounds.

Easy as 3.14159265....

If you'd prefer not to do the calculations, and you also happen to brew 5 gallons batches, I put together a table that shows the amount of DME you'd need to add in order to get a certain yield.


[1] Daniels, Ray Designing Great Beers (Brewers Publications, 1996) p.31 - Table 5.1