Message from Jim Matt, Head Brewer at Rhinegeist:
"We've had some issues with Sherry Ink being foamy when stored warm, far fewer issues when stored cool/cold. We had a QC session recently, and came to the conclusion that there was still some sherry flor residing in the barrels, that got carried into the bottles. Sherry flor is a mixture of yeast and bacteria that ferments sherry, forming an almost pellicle-like film on top to protect it from over oxidation. Indeed this is the species that has caused Sherry Ink to continue to ferment in the bottle. We would suggest storing the bottles cold and drinking them in the near future. We have gotten no off-flavors from the flor in our in house QC panels, just some unintended refermentation in the bottle. We are planning to treat our sherry barrels more aggressively in the future, and also sulfite the beer before packaging to prevent this from reoccurring. Thanks to everyone who has enjoyed it, we just cracked one open the other day (that was stored cold) and it still had a lot of complexity to it."