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Sanity check please...same pre-boil vs. post-boil gravity

Post #1 made 13 years ago
by jakethesnake559
Hi all,

After 6 or 7 BIAB brews, I lashed out and brought a shiny new 40L Birko urn.
Cranked it up for the first time for an APA last weekend...target OG 1.054.

Everything went well and after a 90min mash(66c + 70c mashout), I hit pre-boil gravity of 1.050.
At this stage I thought I was bang on to hit mid 50s post boil, so started drinking :whistle:.

After a 90min boil, I lost about 4L to evapouration.
Took another sample, put it aside to cool and transfered to my 20L cube.
As I was filling the cube, I managed to knock over the post-boil sample :idiot:.
So I took another sample by poured a little bit out of the top of the cube.

After cooling the new sample to around 18c, the gravity was 1.050.

Now perhaps I had way too many beers and stuffed up the reading, but I'm not sure how this could be possible :think:.

My only theory is that the pre-boil sample (from the urn tap) may have had some sediment from the mash.
And that the post-boil one from the top of the cube had hardly any sediment/trub.

Temperature wise, I chilled the pre-boil sample to 10c and the post-boil to 18c.
That shouldn't make much difference I don't think.

I'm not overly worried about it, but has anyone ever experienced this?
Thoughts??

Mental note, don't start drinking till post mash :drink:.

Post #2 made 13 years ago
by Squared
if you trust your thermometer(s) and lost volume during your boil thats all I'd need to know given the weird circumstance. At the very least you could estimate that it would be more than 1.050 and maybe near 1.054. Even if all failed and you somehow really got OG 1.050 thats not all that bad.

Post #3 made 13 years ago
by PistolPatch
jakethesnake559 wrote:I'm not overly worried about it, but has anyone ever experienced this?
Yes. Getting weird readings is totally normal. In fact, beware when anyone says, "I always hit my numbers bang on." It's just not possible in home brewing.

I've got a lot of thermometers and a lot of hydrometers and one refractometer here at my place. I've built these up over the years and taken, on many brews, careful measurements so I think I can safely write the first paragraph here :) .

There's one true thing... "No matter how sober you are on a brew day, a single measurement cannot be trusted." (You have to do a lot of sober brew days to realise this because your brain will always find justifications for why a measurement was wrong or why two measurements don't agree.)

I spend a lot of time helping people with numbers and thinking on them but this is mainly to make sure that new brewers aren't going to totally stuff-up their first recipe which can be easy to do. The 'end of the day' figures often turn out well but that's probably more to do with the last paragraph than anything else :). (Just joking, I hope ;)). Numbers can also sometimes short-cut fault-finding but you always need the average of several numbers before you can make assumptions.

What I'm trying to say is don't worry about your reading jake. Take readings as often and as much as you can if it interests you. If you've got good intuition, don't take any readings, just taste the beer. Either way will work out.

:peace:
PP
Last edited by PistolPatch on 07 May 2012, 23:51, edited 3 times in total.
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Post #4 made 13 years ago
by BobBrews
jakethesnake559,

Normally I don't take any readings at all! Mostly because it's hard to read a hydrometer while lying on the floor trying to keep it from spinning! That being aside. I follow my recipe and (try) to hit the temperatures. I practice the best methods I can in keeping everything that touches my wort sanitized! I ferment at approximately the right temperatures for that yeast! My beer comes out just fine even though I don't know any of my numbers?

So all that I am saying is try for the numbers but don't worry if you don't get them or know them! Beer is forgiving as a mother but you don't have to send cards on mothers day!
tap 1 Raspberry wine
tap 2 Bourbon Barrel Porter
tap 3 Czech Pilsner
tap 4 Triple IPA 11% ABV
Pipeline: Mulled Cider 10% ABV

http://cheesestradamus.com/ Brewers challenge!
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Post #6 made 13 years ago
by jakethesnake559
Thanks guys...the more I brew, the more I learn to relax about stuff.
Was looking to get as much info as possible as it was the first brew with the new urn.
Will take a reading when I get around to transfering it to a fermenter.
Cheers!!
Jake.

Post #7 made 13 years ago
by PistolPatch
jakethesnake559 wrote:Thanks guys...the more I brew, the more I learn to relax about stuff.
That's exactly right jake :clap: :thumbs: :salute: .

Like Bob said, brewing is very forgiving. But. it takes a while to get to this realisation and most brewers don't even remember how they got there :lol:.

Before you can get completely relaxed about your brewing I think you need to make sure of several things. For example, I went to a brew day last weekend at steveM's and one of the brewer's there told me that a few weeks before they had discovered their thermometer was 10 C out at mash temperature! (It read correctly at freezing and boiling point but how many times have you read that if a thermometer is accurate at freezing and boiling, it will be accurate at mash temps?) A new brewer would always trust a thermometer at mash temperatures. Why wouldn't they?

There are many other things like this where a new brewer can go wrong. In the last few days we have been looking at priming rates. One of the world's most respected kit brewers tells you to prime your bottles at almost 1.5 times what a proper priming calculator recommends.

So, to some extent you can get relaxed about your brewing. It's when you get a problem, like nearly losing an eye from a bottle bomb or from finding an obscure infection that only you can seem to taste, you get more interested in procedures and numbers.

So respect some estimates*, ignore a lot and certainly treat your own occasional weird measurements with a grain of salt.

:lol:
PP

* A lot of guys here have been working on much of the above. I think the next change to this site will certainly remove the estimate problem.
Last edited by PistolPatch on 09 May 2012, 22:13, edited 3 times in total.
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Post #8 made 13 years ago
by BobtheBrewer
[quote="BobBrews"]jakethesnake559,

lying on the floor trying to keep it from spinning!

Bob, You aren't drunk until you have to hang onto the floor so you don't fall off while it is spinning!
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