Numbers simply don't add up - a recurring theme

[Zepth]

So I'm about to throw something across the kitchen and regret it later. The thread title says it all, for the first time in my life math is lying to me. And I'm at my wits end trying to figure out what is going on.

The moral of the story is that I can't do a full wort boil. My setup doesn't allow for it nor will it be able to any time soon. So I make do with what I've got, have gotten some good beer out of it and some perfect numbers. Efficiency suffers as a result, I take it in stride. Other times, this happens.

The process: Mash in converted 10g igloo, with false bottom. Take as much first runnings using as little sparge water as possible into every large pot I've got until my stove runs out of burners. Usually in the 3-4 gal range, depending on how much I fill them up. Any more in the giant stock pot just refuses to get boiling. Boil and hop as per the batch instructions. After this use a combonation of kitchen sink and bathtub cooling to get that cold break. Rack into fermenter and check gravity. Analog thermometer and hydrometer.

First time: Not perfect brew logs, but the important numbers (for this anyways) are as follows. OG 1.080 at 3.5 gal, target 5 gal. Add 1 gal of water, and OG drops to 1.036. What? That doesn't add up. According to my calculations it should be 1.062. Temps were not changed during dilution, same hydrometer, same tube, same everything. Write this down as an anomaly and move on with my day.

Last brew day: Not great logs, but similar event. Had a high OG and low volume, added water to bring it up and hit my target OG right down to the thousandth. Old bastard Clone at 1.062. Couldn't be happier.

Today: Much better information immediately available. Also have the recipe (follows) for you folks to check into. Gravity readings pre- boil ranging between 1.086 and 1.045, temp corrected. First reading at end of first pot, last one at the beginning of 4th. Not too scientific data points, but an idea., OG 1.090 at 2.8 gal after cooling. Good stuff, quickly contemplate pitching yeast and abandoning the current plan. Decide to go with recipe. Quick Google and come over here to find out exactly how much to dilute and not miss my OG - have done that already on blind faith. Punch in my numbers and a desired 1.056 and get 4.5 gal total, after adding 1.7. Alright then, let's do this. Add 1.5 gal, measure my gravity... 1.038. Alright now, wtf!? How did this happen?

I just don't get it. The numbers simply don't add up. Even if it was a fried thermometer or hydrometer it would at least be consistently wrong. Not fine one moment and out of whack the next. Water temp and wort temp is within 2 degrees of each other, this is IMO well within tolerances and not going to throw things out of what by 20 gravity points. Now I don't know whether or not to use the number I should have gotten from the online calculator as my OG, or the one that I measured and is right screwed from where it should be. Any help or suggestions would be greatly appreciated, this going all over the map stuff is driving my nuts.

Recipe: Orfys Hobgoblin clone
4.8 kg maris otter
.25kg cara 60 (used caramunich iii)
.20kg carapils
.15kg chocolate malt
45g fuggles (divided 60/30/0)
45g golding (same)
1 nottingham (out, used s-33)

Thanks in advance!

 

[Zepth]

Small update: just got a parti-gyle from that problem batch today and got 1.032 @ 3 gal, sparge water only. Not too shabby for free. Re-boiled the hops and pitched onto some old slurry for mega - ultra - cheapskate approval. See what happens, free science!

Also had an epiphany that would explain all of my woes. It is quite possible that simply relying on dumping water into the top of a carboy to mix thoroughly has failed time and time again. Then pulling a hydro sample from the top of the carboy doesn't actually reflect that of the contents. The more I type this the more I think about it, and the more it makes sense. Fail. Epic fail. I have some hydro sample stored from a previous batch that had this syndrome (bottled the batch today), I may sacrifice it to spirit indexing and get to the bottom of this all.

I'll post back with an update on how things worked out in the end of it all. For the moment leave this up as an archive. Sorry if it was simply a stupid mistake that never actually caused a problem, which made me worry about something that never was.:smack:

 

[scottballz]

Small update: just got a parti-gyle from that problem batch today and got 1.032 @ 3 gal, sparge water only. Not too shabby for free. Re-boiled the hops and pitched onto some old slurry for mega - ultra - cheapskate approval. See what happens, free science!

Also had an epiphany that would explain all of my woes. It is quite possible that simply relying on dumping water into the top of a carboy to mix thoroughly has failed time and time again. Then pulling a hydro sample from the top of the carboy doesn't actually reflect that of the contents. The more I type this the more I think about it, and the more it makes sense. Fail. Epic fail. I have some hydro sample stored from a previous batch that had this syndrome (bottled the batch today), I may sacrifice it to spirit indexing and get to the bottom of this all.

I'll post back with an update on how things worked out in the end of it all. For the moment leave this up as an archive. Sorry if it was simply a stupid mistake that never actually caused a problem, which made me worry about something that never was.:smack:

I was going to say the same thing especially if you poured the water on top of the wart instead of the wort on top of the water.

 

[Trox]

Wort is much denser than water so when you pour the water in most of it is just going to stay on top of the wort which will give you a much lower gravity reading than expected (a very common occurrence in partial boil extract batches). Even if you pour the wort on top of the water most of it will sink quickly so you can still end up with off readings. Also shaking the hell out of it or mixing it really good may not get it completely mixed, but should get you a lot closer to what you would expect.

 

[scottballz]

If you can, Try aerating the mixture with a sanitized paint mixer and a drill. I usually do this before I pitch my yeast anyway to get some O2 in the wort. obviously if you are using a carboy, as your fermentation vessel, you will have to do this before you put it in the carboy. so just get yourself a 6 or 7 gallon bucket, mix everything together, aerate, then add it to your carboy and take a gravity reading.