You can get a lot of filtration capacity by using a 0.45 micron depth
filter to catch the major junk, with a 0.45 micron absolute filter (of
smaller size) downstream of the depth filter to catch the little bit of
tiny stuff that makes it through the depth filter. Depth filters take a
lot longer to load up and are usually rated for 95-99% efficiency,
whereas absolute filters can give you 99.9+% filtration efficient but
load up quickly if you put the dirty wine directly to them.
The more loaded a filter element gets, the greater the chance for 'punch
through' (where high velocity flow in a small area can occur due to the
high pressure drop across the major portion of the filter element).

In all cases, you want to make sure the filter element does not have
gaps around the edges/ends. Those gaps will allow stuff to get around
the filter element. Many people use a permanently sealed cartridge
absolute filter to minimize filter 'seating' problems. If I'm not using
a permanently sealed 0.45 um absolute filter unit, I like to use the
spear-point single open-ended with double o-ring filter types.
There are less expensive double open-ended filter elements that use flat
washers to seal both ends, but they don't seal as well. They USUALLY
seal, but not always.

Commercial wineries typically use a diatomaceous earth pad filter system
for rough filtering, and a 0.45 micron absolute filter just ahead of the
bottling line to catch the odd fragments of yeast and ml bacteria.

Gene

wrote:

> You can get sterile filtration equipment easily down to the 0.1 micron
> range. I purchase 0.45 micron depth filters (nom), which (as of yet)
> have not permitted any re-fermentation of any wine.
>
> I'll let you know in 2 years whether or not the honey meads have
> started back up.
>
> The filter sheets run about 50 cents apiece, and are each easily
> capapble of doing 10 gallons+.
>
> Jason
>
> RD wrote:
>
>>Bob,
>>
>>It sounds like you're talking about the difference between 'polish
>>filtration' and 'sterile filtration'. Polish filtration is often done
>>with a 1 - 5 micron filter. It will not exclude yeast or many other
>>microbes. If you need to remove yeast with certainty you need to
>>filter through a 0.45 micron filter (or smaller).
>>
>>Having said this, Port is usually fortified to nearly 20% alcohol.
>>That should be pretty effective at killing your yeast population.
>>
>>RD
>>
>>
>>Bob Becker wrote:
>>
>>>I'm in the process of making a port wine kit.
>>>
>>>As part of the process they specify filtering to get rid of
>>>the yeast to eliminate the possibility of further fermentation
>>>of the residual sugars once the port is bottled.
>>>
>>>I just re-read the previous thread about filtering, but it seemed
>>>geared toward clarification rather than filtering yeast.
>>>
>>>Is there a difference, or will any filtration system clarify
>>>and also eliminate yeast?
>>>
>>>
>>>--
>>>Bob Becker

>>>www.becker.org
>
>