Corking Your Wine

The last step in winemaking is filling and corking your bottles and few things are more important to the shelf life of your wine than how it's handled at this point. First, your wine has to be finished: clear, stable, and free of CO2.

• Clear — free of particles that could later fall out of suspension and leave a deposit in the bottles.
• Stable — finished fermenting and having enough sulphites (SO2) to prevent oxidation and spoiling.
• Free of CO2 — while fermentation may be finished, your wine can still be saturated with carbon dioxide. If it is, it will go into the bottles with the fizziness intact, and 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?).

For information on clearing your wine, see our handout on fining and filtering. For an explanation of sulphites and their use, get our 'Sulphite Facts' handout. To get rid of CO2, stir your wine. When the fermentation is finished, fining agents are added, 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.

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 harbour 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 sanitise, 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. For more information on cleaning and sanitising get our handout 'Cleaners, Sanitizers, and Preservatives'.

Filling
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 Enolmatic 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 1½ inches long, the wine should be 2½ 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!
The choices for corks includes colmated, agglomerated, synthetic, and natural. There are also many grades available within each type.

• 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.
• 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.
• 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.

Corks are made from the bark of the cork oak, Quercus Suber. There are persistent rumours that the cork forests are endangered. This isn't true, according to the Cork Quality Council. Their figures show the damage is limited to an area of less than 1% of all the cork trees 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.

Wine Cave Inc. sells a variety of corks. For most kit wines we recommend an agglomerated cork, as it will have the combination of quality and value that best suits wines to be kept for up to 6 months. For wines intended to be kept longer we recommend a winery grade cork: slightly more expensive, but it will keep the wine for 1 - 2 years. For the best wines, made from premium kits, juices, and grapes, investing in the top grade of premium corks will pay off over time.

But what about cork length? Should you choose 1½' or 1¾'? Will a longer cork keep the wine longer? The answer turns out to be more subtle than first glance would indicate. How well a cork seals a bottle depends on three things:

1. Cell Density. This is the most important factor. If the cells which comprise the structure of the cork are well formed and sound, a layer 30 cells thick (less than ¼') will stop all movement of wine. If the cells are less than optimally arranged, it can take more layers to prevent leakage. Corks are graded partially on cell density, with the most dense also being the most expensive.
2. Potential Flaws. The presence of pits and areas of uneven density is common to all grades of cork, but again, the most expensive will have the least number of these, and thus will seal more effectively against the neck of the bottle.
3. Contact Length. There are two principal bottle shapes used for wine, the Bordeaux style and the Burgundy style (there are others, but they are less common). The difference between the two is the amount of flaring in the neck. Bordeaux bottles have a relatively straight sided neck throughout it's length, while a Burgundy bottle will flare after about 1½'.

This flaring means that the last ¼' of an inexpensive 1¾' cork may not be in full contact with the bottle neck (with pitting and low density, cheaper corks can't expand enough to fill any flaring beyond the standard 18.5 mm.), this prevents them from sealing the bottle effectively. The best choice for Burgundy style bottles will usually be the 1½' cork, and the length of time the wine will be kept will determine the grade needed.. Quality is more important than length for determining which cork you should use.

But, if a 1¾' economy grade cork isn't substantially better than a 1½', is a 1¾' winery grade cork better than a 1½'? The answer is a qualified yes. Because it has higher cell density and fewer potential flaws it can fully expand to exploit it's sealing power along the full length of the bottle neck. While this increased capacity is more dramatic in Burgundy style bottles, the increase in sealing power applies as well to Bordeaux style.

Premium corks are designed to keep the wine for 3 to 5 years, or longer, given good cellar practices. They also have a price tag to justify their quality—they may not be the best choice for any wine being kept for less than three years.

The table below provides a rough guide to how long your corks will last, given proper handling.

Length	Agglomerated	Economy	Winery Grade	Altec	Premium
1.5'	6 Months	6-18 Months	18 Mo. - 2 yrs	-	3+ years
1.75'	-	-	2-3 years	5+ years	3+ years

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 1½ inch long cork, but ¼ 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.

Handling Your Corks...
A lot has been written on how to treat corks at bottling. Much of this information did not take into account the type of corker being used. Old-style compression corkers use a plunger to force corks through a funnel-style opening into the bottle. While they will push the cork in, they aren't very accurate, and they require that corks be soaked and softened to allow them to slide through the small hole. This soaking can soften the corks to the point that they become mushy, causing them to disintegrate at a later date, or not to properly seal the bottle at all.

If you are using an old two handle or single handle compression type corker, you can soak your corks in lukewarm water for about 20 minutes, and then remove the corks to a sanitized bucket. If you have trouble getting corks to pass through your hand-held corker, you may want to try adding ¼ cup glycerine to every four litres of warm water that you use for soaking.

Newer iris-jaw type floor corkers (Wine Cave Inc. sells them as 'Mini Floor Corker' and 'Deluxe Brass Jaw Floor Corker') are precise and powerful, simultaneously squeezing the cork down and pushing it into the bottle with a leverage arm. If you are using one of these corkers, there is no need to soak or sulphite any of the corks that Spagnol's sells — simply insert them dry.

Once you have opened a bag of corks, you may need to take special care of the unused corks.

After the bottles have been corked, it is important that they be kept upright for two to three days. This allows the air trapped underneath the cork to gently move past it, reducing the pressure in the bottle. If the bottles are laid on their sides right away, the pressure will not be released, and the wine pushing against the cork could force it out of the bottle.

Stand and Deliver: Loose Ends
After all of your bottles have been safely filled and corked, 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 should leave your wine bottles standing upright for at least the first 24 hours after corking. Why? Well, remember the piston-and-cylinder analogy from above? The compressed air has to work it's way out past the cork, and it can only do that if the bottle is standing up. If you immediately turn the bottle on it's side, the pressure will still be there, but the wine will now be pushing against the cork, and could force it out of the bottle. After 24 hours (or two or three days: it isn't critical to do it right away) you should turn the bottles on their side for long term storage. This is when the wine against the cork will keep it moist, preventing leaks.

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 (15°C 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.

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.

Adjusting Your Corker

Wine Cave Inc. mini floor corkers are precision designed, well constructed corking machines, and with proper care and maintenance will last for many thousands of bottles. With occasional maintenance you'll be able to keep your corker in top shape.

Indications that your corker is in need of adjustment are chipped corks, scored corks, incompletely inserted corks, and general difficulty engaging the corking arm. In addition, the bottle platform may stick or slip, and can require adjustment as well.

Adjusting the Jaws

If you remove the three screws holding the top cover on, you will see the inside of the corker housing.

Looking down into the top of the corker, you will see the Y arm and the jaws. The Y arm should be at a 45° angle, holding the jaws squarely together. If it is at an angle of greater than 45°, there will be a gap between the Y arm and the spring loaded jaw. The Y arm will need to be bent back into true. In addition, the screw holding the fixed jaw can loosen over time. This will need to be tightened and re- aligned.

To adjust the Y arm you must first remove the spring loaded jaws. Be very careful when handling these jaws! The springs are quite powerful and could leap out of the corker, making them an eye hazard. Use safety goggles.

1. Remove the jaws by placing a cloth over the top of the open corker. Slide the blade of a screwdriver into the back of the jaw where the spring inserts. Place your hand over the top of the cloth to prevent the jaw from shooting away, and gently lever the jaw up until it is free of the housing. Place jaw and spring where they will not be lost and remove second spring loaded jaw in the same manner. Leave the fixed jaws in place: it isn't necessary to remove them to adjust the corker.
2. Once the jaws have been removed, pull the Y arm out of the housing, so that it pivots on its' connection to the corking arm and sticks up in the air. At this point you will be able to see if the fixed jaw that is connected to the Y arm has loosened. If it has, do not correct it yet: when you bend the Y arm back to true, you will need to move the fixed jaw around to make sure you've got a tight fit for the spring loaded jaw.
3. Using a large wrench, grasp the end of the Y arm and, holding the corker firmly, bend it back to a 45° angle. Don't bend too quickly—you'll just have to bend it back if you go too far. Check the progress of your work by re-inserting the spring loaded jaw into the Y arm (without the spring). This will immediately show you if you still have a gap to deal with, or if you've gone too far.
4. Once the Y arm is back in its' appropriate shape, insert the spring loaded jaw, and, using it like a spacer, tighten up the screw on the back of the fixed jaw. It is important that the screw only be tightened this way: if you do it freehand, without the spring loaded jaw in place, you could change the fixed jaws' position, making it score corks after re-assembly.
5. At this point, it is a good idea to wipe out the inside of the corker, removing any lubricant residue, moisture, or chipped corks. You can then lightly coat all of the jaws with a sparing film of Petrol-Gel.
6. Reassemble the corker: put the Y arm back down into the housing, put the springs inside the jaws and re-insert them, spring end first. Seat them all the way to the bottom of the housing. Remember to wear your eye protection.
7. Examine your work. Your corker should now look like the first illustration, square and true. Reattach the top plate, lubricating the end of the screws with Petrol-Gel. Carefully wipe the inside of the jaws to remove any dirt or excess Petrol Gel, and test-run a few corks—you should be on your way.

Adjusting the Bottle Platform

If the shaft that holds up the bottle support sticks or won't spring back up tighten the two small nuts on the bottom of the spring tensioning arm clockwise. This will increase the pressure on the platform tension bar, freeing the shaft.

If the shaft won't lock in place and allows the bottle to move down before the cork can be inserted, turn the two nuts on the tensioning arm counter-clockwise. This will make the tensioning arm hold more firmly to the bottle platform shaft, keeping it firmly in place during corking.

Things to keep in mind about corkers and corking:

• Keep your corker clean and dry.
• Don't soak your corks.
• If the corks go too far into the bottles, or stick out above the neck, adjust the cork depth with the knurled ring threaded onto the corking finger. Corks should be just below the lip of the bottle.
• Lubricate the jaws with Lubri-Film only. Do not use vegetable oil or glycerin; they will attract dirt and gum up the jaws. Do not use WD 40 or other synthetic lubricants as they are not safe for human consumption.
• Occasionally lubricate other moving parts (i.e., those that do not come into contact with the cork) with WD 40 or other synthetic lubricant to prevent sticking.