when to sample, how to estimate OG...etc.

[fred_zepp]

So I did another all grain batch yesterday...and I missed my OG.

I want to know how I can estimate my OG based on a hydrometer reading after the sparge/pre-boil. Or even during the boil...take a sample and then figure out how much/how long I will need to boil off to get down to target OG.

Is there a book that I need to read? Which one will teach this kind of thing?


An example: my plight from yesterday

Est OG was 1.072. My reading at end of boil was 1.053. Crap. I had already done my aroma hop additions (0 min) . Dang it. I tossed in two pounds of light DME (boiled for 5 mins) and got up to 1.066. Still short. I think part of my problem was too much sparge water.

 

[cvstrat]

That's pretty far off. Maybe instead of worrying about estimating the OG you need to take a look at your process. I don't think sparging too much water is a problem because you're going to boil it off anyway and the sugar concentrates in the wort. As long as you end up with your target volume in the end then it's likely a problem somewhere else.

I got wasted on day and brewed an amber ale. I accidentally put something like 9 gallons of water in for the mash. When I drained off my word I ended up with like 7.5 gallons preboil for a 5.5gal batch. Needless to say I had to bring it to a raging boil for an hour to get down to where I needed to be just to start the regular boil process. But in the end when it was all said and done I was damn near the OG I was aiming for.

Aiming for an OG isn't the way to do it. You aim for a volume, say 5.5 gallons. If you are sure you are hitting your temps on everything, and your grain crush is good, well your system might just not be as efficient as you'd like. At this point you keep all the factors the same but bump up all of your grains a certain percentage to get more sugars in your wort. What you'll wanna do it brew up a proper batch or two, measure your OG after the boil is over and you have exactly the right amount of wort the recipe called for, then you can calculate your efficiency and adjust by the right amt.

 

[beerkrump]

If you post your recipe and process, we'll make fun of you. Uh, I mean troubleshoot it for you.

 

[fred_zepp]

well,

I've got pretty close to 75% efficiency before... i don't think that's the problem. I think what happened was too much sparge water....then I didn't realize until the end of the boil. Ended up with 5.5+ gallons when the recipe was for 5 gallons.

I hit my mash temps perfectly. My sparge water was between 170-175f the whole way through.

The only thing I changed from previous batches was the addition of rice hulls to prevent another stuck sparge. (i have stainless mesh "socks" on a copper tee in my MLT keggle)


I'll get to the recipe later...basically a Hop Rod Rye clone from BYO magazine.

 

[fred_zepp]

So I guess I need to be able to accurately measure volume in the boil kettle.

There is also a rule of thumb for how much volume will boil off per hour correct?

Finally, is there a relationship between OG and volume??? i.e. If I boil off 1/2gallon, O.G. will go up 10 points, etc?

 

[wildwest450]

Get some software!! I use beersmith and love it . It will give you a preboil gravity then you can make any adjustments before the boil. I have never missed a FG by more than 2 points. 80% of the time it's one point or dead on.

 

[Bsquared]

It looks like you say you where .5 gallons over from your sparge? That should not drop you that far on your hydrometer reading. according to my calculation if you have 5gal @ 1.072 and dilute to 5.5 gal your OG will be 1.065.

Did you check your mash pH? If the pH gets to acidic or two basic your efficiencies can fall way off. (Chapter 15 form palmer)

This was a rye beer? I'm not sure of your total grain bill but it might contribute to a change in pH depending on your water profile.

 

[jjp36]

My guess is you got a crappy crush on the rye which is why the efficiency so low. You need to either tighten up the rollers or double crush the rye.

 

[2bluewagons]

according to my calculation if you have 5gal @ 1.072 and dilute to 5.5 gal your OG will be 1.065.

You should get software, but this calculation is not rocket science. The gravity is only a function of your volume. If you can measure volume correctly, you can figure out how much you need to boil off to get your target OG.

pre-boil volume X pre-boil gravity = post-boil volume X post-boiler gravity

So in the above example, 5.5*1.065 = 5*1.072. If you know three of the variables, you can get the 4th.

 

[Gremlyn]

To make it easier on calculating, take the gravity readings and drop off the '1.0'. So if your pre-boil gravity is 1.045, use 45; Designing Great Beers call these 'Gravity Units'.

So if your pre-boil is, as above, 1.045 in 6.5 gallons and you want to hit 1.060 in 5 gallons do the following:

45 GU x 6.5 gal = 292.5 Total Gravity Units
292.5 TGU/5 gal = 58.5 GU

So if you add back on the '1.0', you find out that you will have a wort with 1.059 SG (rounded up) when concentrated to 5 gallons. From here you can figure out how much DME you may need to add to hit your target.

Did you make sure to correct your gravity readings for temperature? As for knowing volume in the kettle, get a sight glass from Bargain Fittings. I measured out by the 1/2 gallon and marked the sight glass. Keep in mind that boiling wort will take up more volume than cooled wort, by as much as a 1/4 gallon in a 5 gal batch. I plan on adding a second marking to my sight glass for heated liquid.

 

[fred_zepp]

Sweet. That is exactly what I needed!!! Show me the math.

Sight tubes will be my very next purchase...I had decided that yesterday whilst standing around scratching my head.

The crappy crush (if so) was courtesy of the morebeer grain mill.

Thanks for the input dudes.

 

[bjzelectric]

Dont forget to use beersmith to correct for temperature with your OG. That makes a big diff. Instead of a sight tube I use a leftover piece of CPVC and I marked it with a sharpie where the surface of my water is @ 1 gal, 2 gal etc. Cheap and simple.

 

[fred_zepp]

yeah, i use a temperature correction chart for the hydrometer.

which of the books out there will teach me all the "math" behind beer recipes, ABV, OG, FG, SRM, etc. ???

 

[Gremlyn]

Designing Great beers goes into the math pretty heavily. I found it quite interesting, even though we have programs to do that all for us now