Also being a fan of the Viking Blod, I decided to try your recipe and change it a bit (mostly by default since I'd never made mead before). I made this in a 2007 44gal white wine (not sure what type) oak barrel from Southern California.
125 lbs yellow clover honey
3oz nugget hops
6oz golding hops
40g Lalvin D-47
2lbs hibiscus flower
OG- 1.754 (it was a little extreme)
I boiled the honey mixed with water in several pots for 30 min at a slight rolling boil. Once all the honey was boiled and added to barrel, I topped it off with water (with room for about two more gallons). I then added the activated yeast. I kept the barrel at about 65 degrees. After six weeks I took the hibiscus flowers and boiled them down and added the water to the barrel. I then kept the mead in the barrel for 11 months. At this point I bottled the mead because there appeared to be no more off gassing.
The mead turned out very good, though extremely heavy on the hibiscus. The color was a bright red and the drink turned out to be more of a sparkling wine. not what I was shooting for, but very enjoyable. There was a strong honey flavor to the mead, but the more the mead was left to flatten out in the glass the heavier the honey flavor. Then about six months later, the bottles began to pop. I think when I bottled it, it started to mix up the sediment and reactivate the yeast.
I'm going to retry the recipe in the same barrel without any additional hibiscus except whats left in the oak. Any thoughts on why this went down the way it did or some ideas for the next one?