Have a batch that started at 1.050 and is currently at 1.020 on Day 12. I pitched 3 day old harvested K97 slurry using Mr Malty calculator. Fermentation took off quickly, was quite vigorous for a few days and then I ramped the temp up to about 70F once fermentation slowed. After a couple of days, I let it naturally fall to about 62F.
I have roused the settled yeast, pitched another packet of yeast, & raised the temp to see no signs of fermentation 24 hours later. Does it take longer to get going since less sugar is left in the wort?
Is it likely that I don’t have a very fermentable wort and that it is just done? I am not sure how that is possible but I am a little clueless here. Been a long time since I have had any problem like this…
Yes ale. I will have to go back and take a look at my notes to see if anything was off from my normal process. I am hoping that somehow it starts back up again but not much more I can do.
is 70% mash efficiency your norm? k-97 for this as described should have finished 1.012-1.014. i would say its done and that’s it. if you’re confident in both mash PH and temp, the other thing would be the slurry…more dead cells than healthy cells-but you will never figure that out.
target pH. I use bru’n water along with my Wards Lab water analysis to make adjustments. It has worked well up to this point but obviously I may be off there as well. pH meter is on the list of things to get…
Anything different about your mash thickness? Kind of grasping at straws here but I have seen some shifts in pH going from a batch sparge to no sparge with same grist and salt/acid additions - not drastic, but there was a difference. But this doesn’t make sense as your efficiency didn’t take a major hit… hmmm. I’m stumped.
Might just be a mash thermometer calibration thing. Easy to check. Boil some water and see what it reads. Don’t forget to adjust boil temperature based on your own elevation on the planet Earth – boiling point is 212 F only right at sea level.
It’s always good to calibrate your equipment properly but I’ve never had a moderate gravity beer finish at 1.020, even when mashing close to 160 F. I guess if a thermometer is waaay off…
I will check it. I calibrated it right when I got it but that was a year ago. It would have to have changed considerably and likely be reading at least 8F to low. Looks like boiling temp at my location should be about 202F
Ph can do strange things sometimes. The calculators are great but sometimes the actual ph will vary unexpectedly. On my last brew day I calculated acid and salt additions for 5.5 mash and sparge, then a preboil of 5.0 ph. I gathered samples along the way. I did two brews with the same profile. After I was all done I did the lab work. Actual ph was 5.5 mash, 5.7 sparge, 5.0 preboil and 5.0 post boil with beer #1. Beer #2 was the same numbers as #1 except that the post boil ph actually went up to 5.1 ph. To me its odd that the calculations were right for the mash, off for the sparge, but then right again for preboil.
Back to your beer. 5.5 target and 152F seems in the ball park but that ph is kind of right on the line between top end for beta and sweet spot for alpha. 152 is getting to the top end of beta sweet spot and bottom end of alpha sweet spot. So a slight ph drift up would easily explain that 4-6 points extra FG. especially if it doesnt “taste” sweet. Dextrins reportedly dont taste as sweet as maltose. Sounds like yeast did its job, you just got a little more dextrinous wort than you expected.
Thanks. I just have never experienced this. 60% apparent attenuation seems pretty severe for this situation but I get what you are saying. I went with 5.5 for a bit smoother of a character in a darker beer. I guess I didn’t realize that pH could affect fermentability to such a degree but I am pretty clueless when it comes to water and chemistry. Before I started treating my water, my mash pH was normally 5.7-5.8 (according to bru’n water) with no noticeable effects on fermentation.
Also, stouts ( being higher in specialty malts, lower in base malt) can finish several points higher than a pale beer of equal OG - this beer isn’t a stout but does have 15% grist from oats and carafa. I wouldn’t expect it to finish 1.020, though. Chris - I assume you accounted for temp and the ‘one degree high’ in your hydrometer reading ?’