Tag Archives: gravity

Apr 202204Mon

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.

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Sep 202124Fri

First the good news. Despite pitching the starter before it had reached peak Krausen – and going straight for 5 PSI – the brew really took off and by next morning there was a very healthy head in the Fermzilla, probably 4 inches and not far off the top of the vessel. At that point I increased the spunding valve to 10 PSI and two days later I had 100% attenuation, equal to about 5.3% ABV via the Tilt Pro.

But then something weird happened: the gravity started going back up. I’ve never seen this before. I’m now on day 11 and we’ve gone from 1.008 on day 3 to 1.014, equal to 71% attenuation and just 4.6% ABV. Could this be an infection or other contamination? My hygiene has been good as usual (though I bet everyone thinks that) and I’m wondering if the brew would have reached peak as far as it did had there been any contamination.

Could it be something to do with the starter? I used a ridiculously small quantity of WLP518 and pitched before the starter was 100% ready, but once again, I had it down to 1.008 in 3 days so … WTF?

One thing you can never rule out is that there’s some stray Krausen stuck to the floating hydrometer and affecting the reading as it breaks down, but while the first generation Tilt was partially susceptible to interference in this way I’m using the Pro version, which is significantly bigger and has never had such issues in the past.

Since I’ve nothing to lose either way I’m going to leave this ferment to ride out and will cold-crash as planned in 3 days time, and then I’ll measure the gravity using my ‘manual’ hydrometer before kegging. As always, fingers crossed.

Leftover Blonde on day 11 of Primary