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stuck fermentation

loki28

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Sep 21, 2017
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Location
Sudbury, ON Canada
I have two batches that are stuck.  An amber ale with OG of 1.046 now stuck at 1.021 for over a week.  The FG should be 1.009.  The other is a porter with OG of 1.066 now stuck at 1.035 for over a week.  The FG should be 1.019.
I used WLP001 for both and used starters for both.  I pitched at 72F and fermented at about 74F.  We did get some unusually warm temperatures for this time of year so fermentation temp may have been higher at some points.  They both had nice krausen within 24 hours so I thought everything was great. 

I have another pouch of WLP001.  Should I create another starter and re-pitch or is there some other solution?

Thanks in advance for any advice.
 
Are you using a refractometer? If so, you need to account for the fact that alcohol refracts differently. There is a conversion thing that you have to set in beersmith for fermenting beer. A Hygrometer would be required to check the conversion factor.
 
This is what I use:
https://www.morebeer.com/images/file.php?file_id=6161

 

Attachments

  • Refractometer_Beer.xls
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You need to make an adjustment for the alcohol content in the readings.  You need to original gravity to do this and use the refractometer adjust tool.  Set the type to 'fermenting wort' and it will convert the reading appropriately.
 
I don't have any dme or unfermented wort so I'm not able to calibrated the refractometer in beersmith2 right now. 
Does that only have to be done once?

I used the spreadsheet Baron posted and my fg's are right where I want them.  Time to keg.

Thanks for your help.
 
I cross-calibrate my refractometer to my hydrometer on each batch, and the calibration factor is different each time. A refractometer measures the index of refraction of the liquid, and they are apparently designed for a solution with only one type of sugar, typical for wine making. Beer wort has a complex mixture of sugars with different refractive indeces, and the mixture you get depends on your grain bill and mash sequence. If you calibrate your refractometer to a hydrometer before fermentation begins, then use one of the well-known formulas to correct the readings for the alcohol content afterwards, you should get fairly accurate results.

Here are the formulas that I use. Using the unfermented wort, take a refractometer reading in Brix (B) and a hydrometer reading in specific gravity (H) and calculate a wort correction factor:

W=B/(((-616.868+1111.14*H-630.272*H^2+135.997*H^3)))

All future refractometer readings will be divided by this factor. To compute the actual SG (G) from a future refractometer reading (R), I use this formula:

G=1.001843-0.002318474*(B/W)-0.000007775*((B/W)^2)-0.000000034*((B/W)^3)+0.00574*(R/W)+0.00003344*((R/W)^2)+0.000000086*((R/W)^3)

I have these built into an Excel spreadsheet, which makes it easy.

--GF
 
I use my hygrometer to double check my pre boil wort to confirm that my refractometer is still accurate at each brew day. I've had to adjust it a few times over the last couple years. Just let the wort cool enough to have an accurate reading.
 
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