First Filtration
After two weeks in the cold, the wine has started to clear. Most of the frozen and dead yeast cells have settled to the bottom of the carboy. It's time to rack and run the Icewine through the filter.
Normally I wouldn't filter any wine until it's clear, but in this case the filtering is done to remove as much live yeast as possible. After racking, I run the wine through two consecutive sets of pads. The first filtration is done using 5 micron pads. For the next, I drop it down to 1 micron.
Yeast cells vary in size from a few microns up to 10 microns or so. Most wine yeasts average 6 microns in size. The successive filterings will remove more than 99% of the yeast. A few will survive, however, we will ensure they are unable to reproduce by adding 220 mg/L of potassium sorbate. I also decided to add an additional 40 mg/L sulfite at this time for a little added insurance.
After filtering I put the carboy in my (slightly warmer) garage, where it will remain for another 2 weeks to continue clearing and cold stabilizing.
Photos below, from left to right: 1) cold wine brought in from outside. 2) The first filtering. 3) Added 2.6 gms potassium sorbate. 4) after the second filtering. The wine still has some haze at this point, but most of the yeast is now gone.
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