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Unexpectedly High Original Gravity

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ivodevo

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Hi All,

I put a brew on of a golden ale in the weekend in my brew in a bag setup, this is the second time I have made this beer and made only minor tweaks to the grain bill to adjust the flavour. I usually mash in 10L, then drain, then sparge the bag in 7L in a separate pot, then drain.

Last time I mashed at 65 degrees, sparged at 65 degrees and came up with an OG of 1.050 (which was what I expected from my calculations in brewpal - with 70% mash efficiency).

However, this time I did the same recipe and came up with an OG of 1.060, with mash at 67 degrees and sparged at 75 degrees.

grain bill is as below (with changes in brackets):

1.2kg Bestmalz Vienna Malt
1.8kg Simpson Golden Promise Ale Malt
0.15kg Bestmalz Melanoidin malt (was 0.10kg for first brew)
0.25kg Weyermann Carapills (was Carahell in first brew)
1.0kg light pilsen dry malt extract

Could it really be that my efficiency has stepped up that much with an increase in sparge temp, to 99% ??? :huh: (Doubt it) Could there be any other reasons? I didn't double check and weigh the dry malt extract, or the grain for that matter... Hydrometer (from the Coopers kit) doesn't look or feel any different to what it normally does.

I am truely stumped... Probably shouldn't have messed around with the sparge temp...
 

grimpanda

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Firstly, accurately measuring your ingredients will go a long way towards consistency.
When ordering your grain it's best to get each grain type in a separate bag and weigh it out yourself before it goes in the mill/mash tun.

Even if you order the exact amount you require for a recipe, you can't always be sure that the employee weighing it out will do it accurately - they might make a mistake, or be careless, they might think you are a top bloke and give you some extra, or they might think you're a prick and give you less. Either way, measure it yourself. A little extra base malt might not make much difference to flavour, but when it comes to specialty malts and especially darker roasts a 10% difference can be huge.

The next thing is accurately measuring volumes. I'm presuming your OG recordings are of your final collected batch volume? If your boil was more vigorous than the previous batch then you will end up with a more concentrated (higher OG) wort. Judging by your grain bill and mash/sparge water, I'm guessing you also top up your boiled wort to reach final volume, so accurately measuring the final volume is important here.

Increasing your sparge temperature should in theory help extract more sugar, so that may well be the discrepancy there, but without accurately measuring your ingredients and volumes there's no way to know.

Another thing to keep in mind (for general consistency and record-keeping) is that your hydrometer reading is also affected by temperature. They are usually calibrated to be accurate at 20-22C, and usually come with a chart for adjustment (otherwise you should be able to find one online). Measuring hot wort should give you a reduced reading rather than a higher one however, so in your case it is unlikely to be the hydrometer playing up.

If you are interested in upping the consistency of your brews the episode titled 'Repeat-ability' of The Jamil Show (a US-based brewing radio show) is worth listening to.

http://www.thebrewingnetwork.com/jamilshow.xml

Happy brewing!
 

iralosavic

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Did you do an iodine test the first time? The ramp to 75c could have converted more starch due to the additional exposure to alpha amalyse stimulating temperatures, but I'm guessing that a miscalculation is involved regardless. Billion dollar mega breweries don't achieve 99% conversion efficiency, so either your gravity or volume measurements were likely out, be it pre or post boil - or both.
 

mwd

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Another possibility is the extract was not fully mixed in when you took the OG reading.
 

ivodevo

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Thanks for the advice everyone.

I agree, 99% efficiency is not possible with my setup. I added the extract prior to boil, so that would have been mixed in properly.

The ferment is now finished (1 week after pitching) and I tested the FG which came out to 1.005 @ 15 degrees. This seemed low so I checked my hydrometer in water, which is reading 0.995 @ 16 degrees.

So it could be the hydrometer that is off? I realise it is now reading too low, so still doesn't make much sense to get a high OG reading... but I guess the moral of the story is that it is time to throw out the plastic coopers hydrometer and invest in a proper glass one.
 

dougsbrew

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I usually mash in 10L, then drain, then sparge the bag in 7L in a separate pot, then drain.

tell me what is your batch size as in how much liquid into ferment vessel, 10 litre mash in 4kg grain, grain will soak alot, + 7 litre sparge im guessing
about 14 litres so 1.060 doesnt sound that high to me. fg 1.005 heaps of alc at 7.4% wow. enjoy in moderation. :)
 

ivodevo

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Sorry, forgot to mention after the boil I fill to the 22L mark :) So was expecting around the 5%...

Checked the gravity with the new glass thermometer (which I checked against water = 1.000) FG comes out at 1.011, not 1.005 as the coopers plaster hydrometer was reading. I should have known not to trust that thing.
 

mwd

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seems the plastic hydrometers and taps in the new Coopers kits are not so good, the price of progress. Still using and being very careful with my original Coopers glass hydrometer that came with the old style kits.
 
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