Question:
I filtered, for the first time, several of my wines this past weekend (under the new Moon).

I used my new PIWC wine filter & the PIWC “Microfine” cartridge. After the Microfine hit its capacity (at almost exactly 60 USGallons), I ran the final 10 Gallons or so through a .45 micron Culligan water filter.

A few observations & questions:

1. The PIWC filter is incredibly efficient, fast & easy to use.

2. All of the wines were already extremely clear prior to filtration.

3. My two residual sugar whites (an Apple with 2% sugar & a Vidal/Gewurztraminer with 1% sugar) went through the filter with no noticeable increase in flow pressure or problems whatsoever. Please note, however, that both of these wines had been fined & both had been aged for several months.

Answer: I'm real glad you did not have problems with the sweeter wines. There was no real reason to suspect you would do. Or was there? In general terms sweeter wines won't filter noticeably slower than dry UNLESS you have high levels of glucans or some other high molecular weight component which may blind the media (even then if you can ever get hold of a media which has the holes punched in it by radiation you may be OK. I don't know if these are made commercially, there used to be a lab filter made by Nucleopore (SP?) which had this feature and the pores did not blind with the glucans. This suggests the structure of a nylon or acetate membrane is significantly different and the glucans etc., build up on the outside of the pore progressively blocking it). Glucans tend to be a feature of botrytis when it has been foggy or excessively humid resulting in grey rather than noble rot. If conditions are good they don't seem to be produced. If you do have grey rot then a dose of glucanase should do the trick trouble is you guys seem to be stuck with using stuff approved for pigs rather than wine! The pressure difference you noted between whites and reds is a bit of a puzzle. You might expect a slight increase between the two (with red being higher) but 10 psi differential seems highish to me