Hi all,

I've been lurking for a few months and gained a lot of information from this site to the point that I routinely add site:gotmead.com to the end of my Google search terms but I have a niggling question about filtration to which I couldn't find a definitive answer: Why is it usually recommended to filter down to 1 micron (sometimes 0.5) to be sure of removing all residual yeast?

All sources I can find state that Saccharomyces cerevisiae cells are in the range of 5-10 microns. I cannot find any reliable source for the size of newly budded daughter cells other than the fact that they are smaller than the mothers. It is my understanding that K-Sorbate prevents yeast cells from dividing but not from fermenting, so it seems to me that any newborn yeasties present at the time the sorbate is added are still feeding, therefore still growing. I would have thought that if filtration takes place some weeks after the sorbate is added, then all yeast cells floating around would have reached maturity. The filter I used has a mean pore size of 2.5 microns with a minimum of 2.0 microns and, more importantly, a maximum of 3.0 microns which leads me to believe that it is sufficient to remove any remaining yeast cells. My father-in-law, who is a retired pharmacist, agrees with me but I wouldn't take his word for it because so far he has been unable to successfully make a single batch of wine - next year his recipe will be to harvest his grapes and give them to me to make the wine.

My first batch of mead is already in the bottles so unless somebody here explains to me why I have made a massive boo-boo which could lead to a sticky floor, that's where it is staying. It would still be good to get a better understanding of where the 1 micron concept originates from people who know a lot more than I have managed to discover.

Although my question is somewhat general in nature, I'll post my recipe below; partly because that's what the forum advice says to do but mainly because I'm really pleased with how it has progressed so far and I want to show off.

9kg wildflower honey.
20l spring water.
10g Mangrove Jack M05 yeast, started with Go-Ferm in some of the spring water.
45 minutes with an aquarium pump and air stone.
45g potassium bitartrate (spring water used had very low potassium levels).
6g calcium carbonate (again to adjust mineral levels of water).
S.G. recorded at 1.112.
Once fermentation was underway, 8.75g Tronozymol (yeast nutrient, mostly DAP with additional micronutrients).
Vigorous stirring with whirly-thing drill attachment for degassing & oxygenating, plus addition of 2.2g Tronozymol twice daily until SG was 1.060.
Whenever pH dropped to 3.2, added calcium carbonate to bring it up to 3.5.
Daily degassing with whirly-thing but on slower speed to reduce oxygenating.
Fermentation settled with SG of 0.995, left to sit on lees for a week, then racked to carboy.
Added 6 campden tablets & 3tsp potassium sorbate.
Waited a week, then back sweetened with 2kg of the same honey.
Waited another few weeks for it to clear.
Got really impatient (I know, not good for mead), added 2tsp bentonite in 250ml distilled water.
Waited another fortnight until it was crystal clear.
Filtered with 2.5 micron filter and discovered what "crystal clear" really means.
Degassed with whirly-thing followed by brake bleeding vacuum pump to -500mm Hg until bubbles stopped forming.
Filled thirty 750ml bottles, left upright for 24 hours.
Waxed the twenty-nine remaining bottles.

It was quite warm so fermentation temperature varied between 22C and 26C.

When bottling, it was just about drinkable but had a bit of a rocket-fuel taste which left a slight tingling sensation on the tongue. There was also a very slight hint of H2S which quickly subsided, honey flavours coming through with a very prominent honey aftertaste. Seemed a little thin so considering a tannin addition to the batch currently in the final stages of fermentation (SG 0.998 and falling) which I will leave dry. The H2S taste was so very very slight that my partner only realised it was there after I pointed it out to her. Will probably crack a bottle or two around Christmas time to see how things have developed then (try to) leave the next sample until early summer.