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.