The last step in winemaking is filling and corking your bottles. They way you seal your bottles is important to the shelf life of your wine.
First, your wine has to be finished: clear, stable, and free of CO2. Clear means free of particles that could later fall out of suspension and leave a deposit in the bottles. Stable means finished fermenting and with enough sulphites (SO2) present to prevent oxidation and spoiling. Free of CO2 means that although the fermentation may be finished, a wine can still be saturated with carbon dioxide.
If it is, it will go into the bottles with the fizziness intact, and depending on the conditions, could expand and push the corks out (or worse, break the bottles), or provide you with the dubious pleasure of drinking a sparkling wine that's supposed to be still (sparkling Merlot, anyone?).
To get rid of CO2, stir your wine. When the fermentation is finished, most people add fining agents, and this is when vigorous stirring is called for. Like shaking up a soft drink, vigorous stirring chases the bubbles out and not only prevents the wine from being fizzy in the bottle, but also helps the fining agents to work better. If you're not using fining agents, check carefully to make sure your wine is free of CO2 before bottling.
You and Your Bottles The first thing you need to do is to make sure you've got the right kind of bottles. A standard wine bottle has a neck opening 18.5 mm in diameter. This will accommodate a standard cork. There are bottles with different neck sizes on the market, and you may encounter some as used bottles. In particular, the flagon shaped bottles from Portugal (Mateus) have a much smaller neck opening, and screw-top bottles have a very large neck opening. Also, with screw-top bottles, the thinness of the glass in the neck area makes them unsuitable for corking.
The second step is to make sure your bottles are clean and sanitary, which are two different things. Clean bottles can't harbor any lurking gunk under a layer of dried wine. If your bottles do have some residue, soaking them in a solution of Sani-brew (the pink cleaning powder) and a rinsing with hot water will clean them up in an hour or so.
To sanitize, just before bottling, rinse them with a sulphite solution. This will prevent the growth of any spoilage organisms in the bottle. The best way to sulphite wine bottles is with a bottle tree and a sulphiter-pump. Used together, they turn a tedious job into a five minute breeze.
Filling the bottles comes next. A sanitized siphon hose and rod are necessary, and a siphon filler is an excellent tool for getting the fill levels right. Consisting of a rigid tube and a one-way valve, it allows carefully controlled filling. It also helps prevent excessive splashing and agitation of the wine, which can lead to oxidation. For people lucky enough to own, or have access to an electric vacuum powered bottle filler, they are a joy to use, and very speedy. For the rest of us though, the siphon filler takes much of the spilling and spraying out of the exercise.
Bottles should be filled so that the wine is about one inch away from the bottom of the cork. What this means is that if you are using a cork 1+ inches long, the wine should be 2+ inches from the top of the bottle neck. This is important: you don't want to leave a lot of ullage (airspace) in the bottles, but you have to leave enough room under the cork for the compressed air to sit.
Compressed air? Well, think of the neck of the bottle as a cylinder. The cork acts like a piston, pushing whatever air is underneath it into the bottle compressing it down. If there isn't enough room for the air, the cork could pop right back out, refusing to stay put in the bottle. The care and attention you take when filling your bottles will go a long way to keeping your wine fresh and unspoiled.
Corks! Corks! Corks! Corks are made from the bark of the cork oak, Quercus Suber. There are persistent rumors that the cork forests in Portugal (representing 30% of the worlds' cork trees) are in danger from industrial pollution, or are hit by disease, or are doomed in some way.
This simply isn't true. According to the Cork Quality Council, the effects of industrial pollution are limited to 10% of a single forest, or less than 1% of all the corks in Portugal (that's 0.3% of the world's cork trees). Also, due to lessened consumption of wine overall, there is beginning to be a reduction in the demand for corks, allowing the home winemaker a wider range of cork choices than ever before.
Agglomerated corks are made from chipped cork pieces ground to a specific size and glued together with a non-reactive polyurethane glue. Inexpensive and easy to handle, these are suitable for wines that will be held for six months, or at most, less than one year. Colmated corks are natural cut corks that are cut from less solid layers of bark, then filled with a glue-cork combination. Slightly more expensive than agglomerated, they are suitable for wines that will be held for up to a year and a half. Synthetic corks are made from inert synthetic resins, and while some wineries have tried them, mainly for short term wines, they haven't proven effective for all purposes. They have to be put in with a heavy duty corker, and can only be extracted with a good worm-type corkscrew wielded by a strong hand. Further development is needed before the home wine maker could put them to use. Altec corks are made from processed cork particles with the impurities removed. The cork particles are combined with Expancels and bound together with a non-reactive polyurethane resin. Altec corks have a more even density than most other corks, which means they seal better and are easier on corkers. In the bottle, they are good for at least five years and perhaps for as many as ten. Natural cut corks are just that: simply punched out from cork bark. They rely on the density and elasticity of the natural cork bark to seal the bottle. Depending on the quality of the cork, you can expect your wine to last from 3 years to more than 10. Another thing that comes in to play when choosing a cork is the bevel. This is the tapered edge that some of the less expensive corks have around the top and bottom of the cork. This is to allow easier insertion with hand held corkers. The thing to remember is that the bevel actually reduces the amount of surface area in contact with the neck of the bottle. This contact is what prevents the passage of wine past the cork. If you have a 1+ inch long cork, but + inch is bevelled off of each end, it is effectively only 1 inch long.
How long should your cork be? Which cork is right for you? Look realistically at how long you expect to store your wine before drinking, and figure out how much cork fits in your budget. A good rule of thumb is 'You get what you pay for.' The cheapest cork isn't always the best deal, and if you do decide to keep some bottles for the future, you may find yourself having to recork them in a few years. In addition, if you are making a wine kit you intend to drink within the next 6 months, a very long cork might be a waste of money.
Preparing Your Corks If you are using a high quality, iris-jawed floor corker (see the next section) there is no need to soak the corks; simply rinse off with sanitized water and insert.
If you are using a small, hand-held corker (single or double-lever types) you may need a little help getting them fully inserted. You may want to try adding + cup glycerine to four litres of warm water. Soak for only a few minutes.
This ensures that the corks get enough moisture to lubricate their passage through the corker, but they won't crumble.
While some books talk about boiling and long soaking in sulphite solutions, these are very bad ideas. Cork is tree bark, and boiling it makes it act just about like you'd expect: it turns to mush and won't seal your bottles. Long soaking does the same thing. Corks can soak up sulphite solutions and transfer them to the wine.
Your Corker: Choosing and Using There are several types of corkers available. We highly recommend a floor corker with jaws that compress the cork like an iris. Other corkers (twin lever, single lever, and compression corkers) rely on human muscles to compress the cork and push it into the bottles.
Irising jaw floor corkers, while more expensive, use simple levers and mechanical advantage to carefully compress the corks and insert them precisely into the bottles. Also, they hold the bottles steady in a spring loaded base. They are really worth the extra money.
After the corks have been inserted into the bottles it's a good idea to dry the top of the cork off with a cloth. This will prevent any moisture there from forming mold on the top of the cork. While a spot of mold on the top of the cork wouldn't hurt your wine, it does look unpleasant.
Keep em Standing After all of your bottles have been safely filled and corked, keep the bottles standing upright for several days. This will allow the cork to re-expand and fully seal. You can choose to put capsules over the neck of the bottle. While not necessary to preserve the wine, they give a nice finished look to your bottles, and when co-ordinated with labels give your wine a professional look. Capsules are often called shrink-caps, because heat is used to shrink the plastic onto the bottle neck, holding it tightly and smoothing out any wrinkles or seams in the plastic.
The best way to apply this heat is with the steam from a kettle. At a rolling boil the kettle will produce enough steam out of the end of it's spout to shrink a capsule in only two or three seconds. Be careful not to burn your fingers!
While you can use blow dryers, they are very slow. Hot air paint-strippers work better, but they aren't as fast as a kettle, and are a bit more dangerous to use. In a pinch the heat from an electric stove element will also serve to shrink the capsules on, but again, be careful with a hot stove.
You may notice mold on top of some of your corks after a few months. This isn't necessarily a sign that your wine has leaked through. It could be that a small amount of wine stayed on top of the cork at bottling and has mouldered there. Carefully wipe the top of the cork and the bottle neck with a clean damp cloth before extracting the cork, and the wine should be fine.
How long will your wine keep? This is a tough question to answer as it depends on so many factors. As long as you keep it safely in a cool (15ŚC or lower), dark room, with good care and attention to your bottling practices, your wine will last as long as the raw materials it was made from. Better quality ingredients usually mean a wine that will age longer.