If you discover sediment in your bottles, this stems from a problem at the clearing and fining stage of your winemaking. But if you discover sediment in your carboy, after the wine has been filtered, that would instead be a filtering problem. Often the issue is as simple as using the wrong filtration pad for your pump. If you have or are using one of the Buon Vino filters, the answer is simple: use the Buon Vino #2 Polishing Filtration pads for everything, and you should have no problems. Except that you should only use the filter pump for filtering, and should not use it while you’re filling the bottles. Doing that could cause problems with the pump itself.
But Buon Vino isn’t the only company that makes wine filtering pumps, and not everybody uses the same designations for their filter pads. So the best way to decide which pad to use is to designate them as 'coarse', 'medium', or 'fine'. These labels refer to the type and size of the particles that the pads are meant to keep from going through.
Coarse filter pads have holes that are too large – or too coarse – to use with kit wines. The big holes in the pads let too many particles go through, and don’t effectively remove those that would cause a haze. Instead, it’s the medium pads that are generally recommended for kits of both red and white wines. After you filter your wine through medium pads, it will show a significant change in clarity and brightness.
Fine pads also do a good job on red wines, though they are usually used for whites. When the wine passes through, these pads remove many of the yeast cells it contains, leaving it sparkling clear. The finer pads will clog up more quickly than the mediums, but this means they are effectively retaining the materials that could potentially cloud the wine. However, medium pads will filter both reds and whites very nicely.
Some pads use a measurement of micron size in their descriptions as well. This refers to the limit on the sizes of the particles they filter out. So a 5-micron pad filters out all particles of that size or larger, while anything smaller than that goes through. The 5-micron pad tends to correspond to the Buon Vino #1 pad, which is the equivalent of 'coarse'. That means you wouldn’t use that size. Since the 1.8-micron pad fairly closely corresponds to the Buon Vino #2 pad – the size recommended for kit wines – that would be the size pad you’d use if you’re going by micron measurement.