As part of our Iron Age brewing experiment I had prepared a yeast ring in advance. Guided by historic instructions which mention a few hours would be needed to rejuvinate, early in the afternoon I added some of the first wort with the ring in a stainless steel starter bucket. For the next couple of hours I kept a clean kitchen towel over the bucket, but found nothing happening… and by the time we should have inoculated the wort, the yeast ring-wort was quiet as the grave.
Sir Arthur Mitchell toured some of the western islands of Scotland in 1768 and recounts how the natives of the Isle of Skye revived the yeast preserved on their wreath:
“The natives preserve their yeast in the following manner: They cut a rod of oak four or five inches in circumference, twist it round like a w[r]ythe, and steep it in fresh yeast for some hours, then hang it up and dry it. And whenever they need yeast they take down the twisted rod, and put it into a covered vessel amongst two or three pints of luke-warm wort, so in two hours thereafter they have fresh barm fit for immediate use.”
The next day, during clean up, I decanted the ring with the still-inactive wort into a brand-new gallon ziploc bag, zipped it, and brought it home to deal with later. To my surprise, guess what I found when the truck was unpacked? One ziploc balloon, with lots of foamy, bubbly activity!
Instead of taking a coupe hours, it took a couple days, but it work, and quite well too. After another day or two of vigorous fermentation the yeast was slowing down and I carefully removed the ring by its cord. I dried it outdoors, on a breezy and sunny day. It was visually dry within a few hours, which was quicker than I had expected. I gave it some more, as the weather was nice, and then stored it in another Ziploc bag in the fridge. In another month, I’ll revive it again, and see if we can get a quicker start. And if not, I’ll just start my ring the day before a traditional brew day, that’s OK too.
This yeast ring is made for me by Robert Hedstrom, from paint stirring sticks (likely pine) and is about six inches in diameter. I like the smaller size as it is easy to store and fits in my smallish stainless steel milking buckets. The yeast ring is inoculated with the standard Safale WB06 dry ale yeast, and is therefore now dedicated to this strain. This ring is a trial to test technique for using the more finicky kveik yeasts, the traditional Norwegian homegrown yeasts, and until then it will serve us well during traditional brewing demonstrations.
Reference
- Mitchell, Arthur. James Robertson’s tour through some of the western islands, etc., of Scotland in 1768. Proceedings of the Society of Antiquaries of Scotland, Volume 32. Society of Antiquaries of Scotland, 1898. https://books.google.com/books?id=-vacElTywOMC&dq
Medieval Mead and Beer 