This makes no sense

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Paddington
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This makes no sense

Post by Paddington » Tue Oct 02, 2018 2:04 pm

I have done maybe 25 AG brews, so I wouldn't class myself as an old timer but I'm also not a complete novice and I'm confident of all of the measurements I've taken but this makes no sense to me.

I've just done a 10l mini brew of a heavily hopped US IPA. I was aiming for an OG of about 1.048. I batch sparked 12 litres into my boiler and the pre boil gravity was very high, around 1.045. I took a second sample to check. I added an extra litre of water to compensate. The hop schedule amounted to 100g.

When I came to put it into the fermenter, I had 8litres. I liquored it back to 10 litres and the OG is now 1.042. I even put the water I used to liquor back through the hops.

I haven't spilled any, so where has the sugar gone???

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Re: This makes no sense

Post by Robwalkeragain » Tue Oct 02, 2018 2:16 pm

I assume something interfering with the reading - temperature, solids in wort, etc. What do you mean by you put the water through hops?

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Re: This makes no sense

Post by Paddington » Tue Oct 02, 2018 3:05 pm

I drained the brew from the boiler into the fermenter through a sieve (it's such a small brew). When I realised it was short, I poured two litres of sanitary water through the hops in the sieve, obviously hoping to flush out any remaining wort (plus a bit of hop flavour!).

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Re: This makes no sense

Post by gr_baker » Tue Oct 02, 2018 3:29 pm

As Rob says it's probably a suspect reading for some reason. The hops will absorb wort but not as much as that.

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Re: This makes no sense

Post by Paddington » Tue Oct 02, 2018 3:41 pm

I retook the pre boil reading several times. I've just gone to the fermenter and retaken that one, plus I've tested the hydrometer with clean water.

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Re: This makes no sense

Post by chefgage » Tue Oct 02, 2018 3:55 pm

Paddington wrote:
Tue Oct 02, 2018 3:41 pm
I retook the pre boil reading several times. I've just gone to the fermenter and retaken that one, plus I've tested the hydrometer with clean water.
I take it you have compensated for temperature?

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gr_baker
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Re: This makes no sense

Post by gr_baker » Tue Oct 02, 2018 4:06 pm

OK if your measurements are correct then you had 12 litres at 1.045 which you added a litre of water to giving 13 litres at roughly 1.042. Post boil you ended up with 8 litres which you added water to giving 10 litres at 1.042. Losses due to evaporation don't lose sugars so somewhere you've lost 3 litres due to hop absorption and/or something else.

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Re: This makes no sense

Post by guypettigrew » Tue Oct 02, 2018 4:11 pm

Here's a thought.

Your 12 litres at 1.045 would have become 13 litres at 1.041.5 when you added that extra litre of water.

Let's assume your readings are all correct and you ended up with 10 litres in the fermenter at 1.042 after liquoring back. To get a gravity of 1.042 after boiling, running off the hops and liquoring back (from the gravity of 1.041.5 before the boil) you should have ended up with a total hopped wort of 12.8 litres in your fermenter. These numbers are calculated using simple arithmetic, nothing clever!

This means you have 'lost' 2.8 litres of wort somewhere between the boiler and the fermenter. A sieve wouldn't hold 100g of wet hops, so I'm guessing you poured the wort through the sieve, but left a fair few of the hops and trub behind in the boiler.

My guess is that somehow you were left with the 2.8 litres in the hops in the boiler. It seems like a huge amount for them to have soaked up but, if your readings were all correct, then it's not possible for the sugars to have gone anywhere else.

Guy

Edit gr_baker just said the same thing!!!

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gr_baker
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Re: This makes no sense

Post by gr_baker » Tue Oct 02, 2018 4:36 pm

ah but you put it so much more eloquently than I did Guy ;-)

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Re: This makes no sense

Post by Paddington » Tue Oct 02, 2018 5:55 pm

I can see how I’d lose some to hops, but that shouldn’t be more than 600mls (6mls per gm apparently) and if it was excessive evaporation then obviously the SG would be ok once I diluted it so, in the absence of any other explanation, I can only think my hydrometer is faulty.

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Re: This makes no sense

Post by guypettigrew » Tue Oct 02, 2018 6:54 pm

Easy to buy another hydrometer if you need one. But you said it read fine in water?

Guy

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Re: This makes no sense

Post by Paddington » Tue Oct 02, 2018 7:03 pm

Yes, I’m clutching at straws. It just makes no sense.

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Re: This makes no sense

Post by Paddington » Tue Oct 02, 2018 7:59 pm

chefgage wrote:
Tue Oct 02, 2018 3:55 pm
Paddington wrote:
Tue Oct 02, 2018 3:41 pm
I retook the pre boil reading several times. I've just gone to the fermenter and retaken that one, plus I've tested the hydrometer with clean water.
I take it you have compensated for temperature?
Sorry, missed this, yes I did.

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Re: This makes no sense

Post by guypettigrew » Tue Oct 02, 2018 9:35 pm

OK. So, all the measurements were correct? The hydrometer reads true?

If you didn't lose 2.8 litres of wort in the 100g of hops (and I've lost this much before I changed my method for running the wort from the boiler), then there's only one final possibility.

The evil wort goblins have jumped into your brew and sucked up all the sugars!

Sorry. That was a bit flippant! But you can't lose sugars.

I've had this sort of hideous inefficiency before. Always been down to a loss of wort in the boiler. I'm still vexed by my overall efficiency. 95%+ in the mash, according to Graham Wheeler's beer engine. 85% overall efficiency. All down to losses in transferring the wort from kettle to FV.

One day I'll crack it!

Guy

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Re: This makes no sense

Post by Kev888 » Wed Oct 03, 2018 12:31 pm

I've done a few calculations; if the only potential source of loss was to 100g of hops then I agree with the above, the numbers aren't what I'd expect. The sugars don't evaporate, they just get more concentrated or diluted, so unless there was some loss of them other than to the hops, IMO there can only really be a measurement error of some kind going on.

The usual suspects of course are gravity, volume, and/or temperature. Personally I'd be especially suspicious of the volumes here, since in small batches a relatively minor volume difference can have a large effect. For instance if the Kettle and FV volume scales don't quite agree, or something like that. Similarly the actual amount lost to hops can vary quite a bit and there were (proportionally) quite a lot of them here. To nail it down in future, recording more volumes and gravities could be helpful - particularly those post-boil in the kettle, and also in the FV before any liquoring back.

This is likely teaching you to suck eggs, but just for completeness: make sure the wort in the kettle or FV is properly mixed and uniform before taking a sample, that it is cooled to whatever the calibration temperature of your hydrometer is, and isn't so full of debris that it affects the reading. If you're using more than one hydrometer then check you get the same readings from both (at wort-like gravities, not just water). If there is a refractometer involved in any readings then be especially careful with that - most need a small wort correction factor, and its also easier to get an unrepresentative sample (it being so small).
Kev

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