A fairly uneventful brew day today with just two small hiccups, #wisdom to follow: I fitted the wrong batteries to my blue Tilt, and I may have been logging gravity readings totally wrong in Brewfather up to now.
Tilt Batteries
After removing the failed lithium AA batteries from my blue Tilt Pro a few weeks ago, I fitted some high-capacity alkaline batteries which I had to hand, mainly out of curiosity to see how long they’d last. Turns out that the digital hydrometer is actually calibrated to use Energizer Lithiums and any other AA battery won’t work, not because of the voltage but because of the weight. My blue Tilt sank like a stone and had to be fished out – didn’t even send any readings back while it was down there because the angle was wrong and it had gone back to sleep.
#wisdom: when replacing batteries in a floating digital hydrometer, use the same ones that it shipped with.
Gravity Errors?
My brewhouse efficiency had been suspiciously good these last few brews, and I was beginning to think I’ve got this licked, but today a thought occurred to me: maybe I should be logging pre- and post-boil gravity values raw, and not correct them for temperature.
Take today’s pre-boil gravity for example. I read 1.046 at 62.8℃, which corrects to 1.063. Slide over to Brewfather and the pre-filled pre-boil gravity field shows a predicted value of 1.048. My corrected value is an enormous 15 points over that, which is an unrealistic level of efficiency. Same story for the post-boil, where I read 1.058 at 51.9℃ – corrected as 1.070 – against a predicted 1.052. Here’s how those two scenarios compare:
I think it’s safe to say that I’m not going to get 98% mash efficiency when a community sourced equipment profile for the Brewtools B40Pro expects 79%, so I’ll have to grudgingly admit that I’ve probably been entering pre- and post-boil gravity incorrectly up until today. I do have the raw values (cheers to decent brew notes!) but I don’t think I’ll bother going back in order to correct the stats for beer that’s already been drunk. Let’s treat this is a learning opportunity instead.
#wisdom: enter ‘hot’ figures for pre- and post-boil gravity in Brewfather. Pre-boil will be straight after sparge (or mash, if there is no sparge) and post-boil will be before chilling.
Update 15 Sept 22: Brewfather expects temperature-corrected hydrometer readings, not raw values.
Brew Day Notes
0810 – Mash rest done. Looks like 32 litres mash tun volume (grain + liquor). Starting Mash.
0835 – Stirred a couple of times, and the wort seems to be running clear again fairly quickly now where at first it took some time. Mash seems thinner too – was fairly cloying at first.
0910 – Heating to 75℃ for mash-out
0925 – Pre-sparge SG 1.065 (1.047 / 62.8℃) volume 31 litres (with malt pipe)
0930 – Start sparge
0937 – Sparge complete. SG 1.063 (1.046 / 62.8℃) volume 30.5 litres (without malt pipe)
1005 – Start boil, 60 minute additions in.
1033 – 30 minute additions in.
1115 – Starting hop-stand
1135 – Hop-stand done, starting chill.
1151 – Forgot to measure kettle volume after hop-stand, but SG is a whopping 1.070 (1.058 / 51.9℃)
1205 – Transfer finished, pitched half a pack of Hornindal (521?) and deployed blue Tilt Pro with alkaline batteries. Fermzilla volume bang-on 23 litres.
1215 – Tried to attach, but no signal from blue Tilt. Will wait a bit and maybe fish it out after clean-up.
1233 – Blue Tilt was spotted near bottom of the FV. Red Tilt deployed too and floating fine, BLue fished out with ladle. Seems like the device is calibrated to use Energiser Lithium batteries, and Alkalines are too heavy for it to float, and it then goes to sleep. Lesson learnt.
1300 – Clean-up finished.