To Filter or Not?

To date, with the few wine kits I have made, I have never filtered the wine before bottling.  Most of the wine kit instructions recommend filtering because it supposedly enhances the clarity of the wine, and removes some of the residual yeast cells that are still floating around.  With my valpolicella kit, the store gave me a coupon for a half day filter rental, so I decided to go ahead and try filtering this wine before bottling.  The store gave me a "Buon Vino Mini Jet" electric filter for the afternoon:  http://www.buonvino.com/minijet.html

The wine filter consisted of a pump connected to an arrangement of plates that force the wine to pass through a sequence of three filter pads, and then through an outlet to a long piece of tubing that carries the wine to a carboy for storage until bottling. The edges of the filter pads are exposed, which allows some wine to escape.  This is probably good for the pump, because if the filter pads get clogged, wine can escape through the sides, which prevents the pressure from building up.  Any overflow wine is collected in a drip tray which drains to a holding container via a length of tubing.

My valpolicella wine had been sitting for some time after clarification, and there was an inch of precipitate at the bottom of the carboy.  So, before starting, I racked the wine into a clean carboy.  This way, I didn't have to worry about the fine solids clogging up the filter pads.  I noticed that the racked wine was already pretty clear.

After the somewhat fussy process of sterilizing the pump and tubing, rinsing with cold water, and flushing water through the filter pads, I began filtering.  I was pleased with the filtration rate, which was a lot faster than what I usually get when I siphon wine from one container to another.  When the carboy of unfiltered wine was empty, I filtered the two litres of overflow wine.

The filtered wine was 'agitated'.  That is, there was a fine foam on the surface, which is meant to be the result of carbon dioxide out-gassing from all the mechanical agitation that happens during filtration.  It took a few hours for the foam to disappear.  As per the instructions, prior to bottling, I let the filtered wine stand overnight in a carboy fitted with an airlock.

Bottling was uneventful, and a sample of the wine tasted much like it did when I first tested it.

30 bottles of filtered Valpolicella

So, was filtration worth the effort?   Filtration seems like a really good way to degas the wine if there is any excess carbon dioxide or sulfur dioxide present.  It is probably a good way to remove any of the finings that are left in the wine after racking, but this only applies to instances of sloppy racking.  If you are careful with racking, your wine should be very clear and may not even need to be filtered.

I personally found it to be a fussy process that creates a number of opportunities to contaminate the wine (e.g. sterilizing and rinsing the wine filter is not easy because of all the little grooves and small parts).  Plus, the whole process is clearly a very good way to aerate the wine: the wine is squeezed through filter pads with high surface area (in air); the overflow wine sits in an open drip tray before flowing into an overflow container; the filtered wine flows at a high rate from the outlet tubing, and this created a sort of waterfall effect in the final carboy, mixing up the wine with lots of little air bubbles.  Basically, there was a lot of aeration.

Would I do this again?  On balance, probably not.

Valpolicella Racking, Stabilizing, and Degassing

Today, I racked, stabilized, and degassed the Valpolicella wine.  The kit instructions are to do this at day 14, but this is day 19.  I let the wine sit an extra five days because the fermentation was not quite complete at day 14.


After the usual sterilization of equipment, I transferred the wine to a clean carboy via autosiphon, without incident.  During this 'racking' step, I took a sample for a tasting.  Well, well, this is nice stuff.  This wine is dry and gentle.  There are woody and nutty tones with a hint of almond.  The tannins are noticeable at the end.  I have hopes for a very nice table wine that will pair well with pasta dishes.

Tasting.  Note-taking is important when it comes to stuff like this.

The specific gravity was 0.990.  From the starting point, this gives approximately 16% alcohol.  Yes, it's pretty dry.


The next step is the addition of potassium metabisulfite, which is provided with the kit.  Out of curiosity, I used my little portable balance to measure the mass of K₂S₂O₅.  The mass of K₂S₂O₅ was 4.4 g.  For comparison, I weighed a Campden tablet.  It was 0.6 g.  The recommended use of Campden tablets is 1 tablet per gallon of wine.  This is a 23 L kit, which is about 6 gallons.  6 gallons x 0.6 g per gallon = 3.6 g worth of Campden tablets.  So, this amount isn't too far off.

When you add the K₂S₂O₅ to the wine, SO₂ gas is formed (see picture).    The chemistry of this step is quite straightforward, and one of these days I'm going to write a blog post about it.

SO₂ bubbles.  You can get rid of the excess gas by stirring vigorously.

After the K₂S₂O₅, I added potassium sorbate and then a small packet of kieselsohl.  Tomorrow, I complete the addition of clarification agents, and then I wait three weeks until bottling.

Valpolicella Wine Kit

A couple of months ago, I bought a wine kit that was on sale:  Wine Kitz Traditional Vintage Valpolicella.  It is meant to be a nice table wine.  This last weekend, I finally got around to starting it.  The kit consisted of 10 L of concentrated valpolicella grape juice and packets of yeast, potassium metabisulfite, potassium sorbate, kieselsohl, and chitosan - all the consumable materials you need.

Naturally, you start by sterilizing all of your equipment.  Then, you simply mix the grape juice with enough water to give you 23 L and sprinkle the yeast packet on the surface.  The fermentation starts up quickly -  more or less as soon as any dissolved oxygen is used up by the yeast.

10 L bag of valpolicella grape juice

The fermentation is now in progress inside a large plastic bucket.  The bucket has a loosely fitting lid which allows the carbon dioxide gas to bleed out.  Because of this small amount of gas escaping, the room has a background of fruity/bakery sorts of aromas.  The home office always smells nice when something is fermenting.

A little peek under the lid to see the primary fermentation (day 3).