Here’s a great question from one of our customers about using wine cork vs screw cap wine bottles. I thought this would be great to share!
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I live very close to a winery and use their used wine bottles for bottling my homemade wines. Sometimes they use cork wine bottles and screw cap wine bottles for the same wine. Do you know why this would be?

Name: William B.
State: Virginia
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Hello William,

Thank you for such a great wine making question. I’ll see what I can do to clear up why you would see a winery use both wine cork and screw cap, and more specifically, why a winery would use both on the same batch of wine!

Here’s the basic pros and cons of using one over the other.

Using screw cap wine bottles will extend the life of a wine. The screw caps make a perfect seal, not allowing any air to seep into the wine. This perfect seal extends the wine’s shelf-life. You could have a screw cap wine be fantastic for 7 or 8 years that otherwise would have only been at its best for 4 or 5 years under cork.

But this “perfect seal” also extends the amount of time the wine needs to mature into a drinkable or – in the case of a winery – salable wine. In fact, it could take up to twice as long for the wine’s maturation process to plateau. This means more inventory sitting in the racks that can’t be sold.

On the other hand, wine corks facilitate the aging process a little more freely. A natural cork allows minuscule amounts of air to pass by it. Over time, this trace amount of air will facilitate the wine’s ability to age and become more drinkable sooner. The downside is that the entire life of the wine will be shortened. So while it will be ready for market sooner it will not last as long on the shelf.

It is possible that the winery corked some of their wine to sell earlier and used screw caps on some to sell later. In effect, this would time out the aging of the wine so that there would be more wine reaching peak maturity over a longer period of time. However, this is only speculation on my part.

There used to be great debates over the use of screw caps. Whenever someone saw a wine under a screw cap they automatically thought: cheap or low-grade wine. That’s absolutely not the case today. Whether a winery uses wine cork vs screw cap is a matter of wine treatment, a calculation of sorts that has nothing to do the the aesthetics and everything to do with maximizing the quality of the wine.

In general, you will discover that lighter-colored wines with less body, such as a Zinfandel Blush or a Chablis are more likely to be under screw cap. This is not because the wines are of low quality, but rather, because the wines are anticipated to fully maturate more quickly than most and do not need the air seepage the natural wine corks provide. They need the air-tight, screw cap wine bottles to slow the process down.

This principal of controlling how a wine ages can be incorporated into home winemaking as well.

Whenever you are ready to bottle a wine, first think about how long the wine could potentially be shelved before it is all consumed: 1 year, 3 years, 3 months! Think about the color of the wine. Is it a white wine that is at risk of oxidation? Are the grapes used to produce the wine known for producing complex, rich wines that can take advantage of abundant aging, or are the grapes known for being crisp, fresh and quickly aging?

When you consider such factors you can start to come up with your own plan and know how to handle the question of wine cork vs screw cap. If your wine’s do not sit around long, go with the wine corks so they can get some aging in. If your batches of wines tend to sit around for years before being consumed go with screw cap and so on with other considerations.

William, I hope this answers the question you had about wine cork vs screw cap. As you can see, there is definitely a reason for using one over the other.

Happy Winemaking,
Ed Kraus
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Ed Kraus is a 3rd generation home brewer/winemaker and has been an owner of E. C. Kraus since 1999. He has been helping individuals make better wine and beer for over 25 years.

I have several 2 1/2 gallon jugs of wine going at this time started in December. The problem is – I am satisfied with the taste and the alcohol content however they won’t stop working. It seems like in the past, when I have allowed the wine to stop fermenting on its own, the taste changes? I have read that potassium sorbate does not completely kill off the yeast? What can I do to stop the ferment at this time and how much alcohol (brandy?) would I have to add to stop the ferment. Thanks.

Name: Skip K.
State: MN
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Hello Skip,

The first thing I’d like to point out is that stopping a wine fermentation is not normal. What is normal is letting the wine fermentation continue until all the sugars in the wine must have been consumed by the wine yeast. If you prefer your homemade wines sweet, you would add sugar to taste at bottling time, and then add potassium sorbate to eliminate a chance of re-fermentation in the wine bottle.

What also is not normal is having a wine fermentation continue on for months. A typical wine fermentation will last anywhere from 5 days to two weeks. The fact that yours has lasted for months tells me that there is something fundamentally wrong.

I would suggest taking a look at the Top 10 Reasons For Fermentation Failure that is listed on our website. It runs through the most common reasons for a wine fermentation to either fail to start or to drag out, such as the case with yours. See if any of the top 10 reasons ring true to your situation. Now on to your question…

What can I do to stop a wine fermentation?
Well, what you can’t do is use either sulfites such as Campden tablets or use stabilizers such as potassium sorbate. Neither of these will stop a wine fermentation with any dependable success. Here’s why:

• Sulfites (Campden tablets, sodium metabisulfite, potassium metabisulfite):
  Wine yeast are bred in such a way as to be acclimated to sulfites. They can withstand the levels that are typically present after a dose has been added to a wine. It is true that if a wine fermentation is on the verge of stopping anyway – for whatever reason – that a dose of sulfite can hasten its ending, but not with any predictable consistency. If a dose of sulfite is added to a fully active wine fermentation, you may see it slow down, maybe even to a crawl, but it would then eventually recover and go on to completion, but usually at a annoyingly slower pace than before. What happens is the sulfite will kill a portion of the yeast cells, stunting the fermentation activity, but then the wine yeast would slowly begin to recolonize and continue on with the task at hand.

• Potassium Sorbate:
  Adding potassium sorbate to a wine fermentation will not hinder it in any way. What it will do is stop a wine yeast colony from regenerating itself. The potassium sorbate puts a coating on the yeast cells that make it incapable of reproducing itself. In other words, it makes the wine yeast sterile. This makes potassium sorbate an effective ingredient to add to a wine that is already clear but may have some trace amounts of wine yeast still in it. If you sweeten that wine before bottling, the potassium sorbate will eliminate any chance of these few yeast cells from growing into large enough numbers to create a fermentation within the wine bottles.

As you suggested, you could add alcohol to the wine to stop the wine fermentation. This is known as fortifying the wine. But you would need to get the alcohol level up to about 20% for this purpose. Brandy is typically used for this. It should be noted that this will dramatically change the wine’s flavor. The wine will seem less fruity as the alcohol level rises.

If you absolutely, positively, without question, must stop a wine fermentation in midstream, here’s how a winery would do it:

1. Chill Down The Fermenting Wine:
   The cooler the better, but 50°F. is sufficient. This will stop the wine fermentation, and the wine yeast will slowly begin to settle to the bottom. You may also want to add bentonite while chilling the wine to help the wine yeast clear out faster and more thoroughly.

2. Rack The Wine Off The Sediment:
   Give the wine plenty of time to clear up before racking it. Technically, it is possible to rack the wine in as soon as 5 days, but it is much better to wait a couple of weeks. You could get extra solids precipitating out of the wine during this extra time such as acid crystals. That would be a good thing.

3. Filter The Wine:
   When I say filter the wine, I do not mean to drip it through some cheese cloth or a coffee filter or something along this line. You need to be able to put it through an actual wine filter that will filter fine enough to remove any leftover yeast cells. This means filtering down to .5 microns in size. A coffee filter only filters down to about 20 to 25 microns. A .5 micron filter pad will remove over 99.9% of the wine yeast in a wine and is considered sterile. Depending on how much tannin is in the wine, you may need to put the wine through a more coarse filter pad first. I always filter through a 1 micron filter pad before attempting to run the wine through a .5 micron filter pad. This eliminates the chance of the filter pad being clogging up with wine solids.

So there you have it: how to stop a wine fermentation. My personal opinion is that the effort is not worth it from an individual winemaker’s perspective. It is much less work to let the wine fermentation complete on its own, then deal with adjusting the sweetness to your liking.

Happy Winemaking,
Ed Kraus
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Ed Kraus is a 3rd generation home brewer/winemaker and has been an owner of E. C. Kraus since 1999. He has been helping individuals make better wine and beer for over 25 years.

This will be my 3rd season of making wine. I have had some that were excellent and some that weren’t. I have not done anything with acid testing wine. I believe if I do I will have more consistency. Can u explain in more detail the timing and amounts of acid testing. I have purchased the pH test strips to start with. I have read previous blogs and that has not given me enough info.

Name: Jon
State: Wisconsin
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Hello Jon,

You will want to use the pH test strips to verify that the wine must is in the right range before starting the fermentation. When acid testing wine at this time you should expect a reading of 3.2. to 4.0 on the pH scale. If you are following a wine recipe this will normally be the case. A proper acid pH range is important for having a sound fermentation and to protect the wine from the growth of unwanted microbes.

If your wine is not in this pH range then you should make adjustments: either add water to lower the acidity or Acid Blend to raise the acidity. Remember: the pH scale work backwards – the lower the number the higher the acid. If your acid level is extremely high you may want to use more drastic measure such as adding Acid Reducing Crystals in the fermentation instead of dilution with water, but it would be unusual to have to go that far.

You should also acid testing the wine, again, before bottling. The acidity level will almost always change slightly during a fermentation, so expect a different pH reading than from before. From a taste perspective you would like the wine to be somewhere around 3.6, but the optimal reading can be different for each wine depending on the character of the wine.

Before making any adjustments such as adding more Acid Blend, etc., taste the wine and make an evaluation yourself. Acidity has to do with the tartness of the wine as well as its stability. Is the wine too tart or too flat – regardless of what the pH strips say? The whole goal is to get it the way you like it.

You may also want to consider using a Acid Titration Kit at this stage for acid testing wine. It is easy to use and is quite helpful to take a titration reading at bottling time. A titration reads the actual strength of the acid in the wine, not the amount of acid like the pH test strips. The amount and strength of the acids do not directly correlated because some acids are stronger than others, and any wine has a mixture of acids varies from one wine to the next.

So, A titration reading relates to taste, whereas pH is more related to how many acid molecules there are in a sample of the wine. Different acids have different strengths or tartness, so you could have two wine’s with the same pH but with different perceived level of tartness. You can read more about the relation of these two readings in, In Plain English: The Difference Between pH And Titratable Acidity In Wine.

I would also suggest taking a look at an article on our website titled, Getting A Handle On Wine Acidity. It goes into more detail on acid testing wine and how to actually control the acidity

Happy Winemaking,
Ed Kraus
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Ed Kraus is a 3rd generation home brewer/winemaker and has been an owner of E. C. Kraus since 1999. He has been helping individuals make better wine and beer for over 25 years.

I bottled some blackberry a few months ago. When I opened a bottle today it fizzed over and kept bubbling for a while. What did I do wrong, I followed a wine recipe?

Name: Ed W.
State: FL
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Hello Ed,

Sorry to hear that your wine has gotten a little out of control. Let’s see if we can figure out what’s going on. If you find yourself asking, “Why is my homemade wine fizzy,” keep reading.

There are basically two ways a homemade wine can end up fizzy or bubbly. I’ll go over them here:

1. Re-Fermentation:
This is the most common way to get a fizzy wine. When a fermentation stops it usually means that it has finished. That means all the sugars in the wine must have been fermented into alcohol. There are no more sugars to ferment.

But on occasion a fermentation will stop before the sugars are all gone. This is known as a stuck fermentation. This can happen for a number of reasons: wrong fermentation temperature, using distilled water, etc. (see The Top 10 Reasons For Fermentation Failure) For this reason it is important that you check the must with a wine hydrometer to confirm that all the sugars have been fermented before moving on to the next step.

If you continue on with the wine recipe and end up bottling the wine with sugars still in it, then a fermentation could start up within any or all the wine bottles at any time in the future, even months down the road. It is important to remember that even the slightest amount of fermentation can cause a lot of fizzy within the wine.

The only exception to the above is if you have added potassium sorbate to the wine, also known as wine stabilizer. If you have added this before bottling, then the chance have having a re-fermentation within the wine bottles is greatly diminished. The same holds true if you have sweetened the wine before bottling. You need to add potassium sorbate along with the sugar to eliminate a potential for a re-fermentation within the wine bottle.

2. Bacterial Infection:
This is not as common of a reason for a homemade wine being fizzy as a re-fermentation, but it happens. If the fermenters, stirring spoons, hoses, wine bottles, corks and anything else the wine comes into contact with has not been sufficiently sanitized, then you run the risk of infecting your wine with a bacteria.

There are many excellent sanitizers on the market. We recommend Basic A because it is very safe and simple to use. You should also add sulfites directly to the wine after the fermentation, and again, right before bottling the wine. If you miss killing some bacteria, then adding sulfites such as Campden tablet or sodium metabisulfite to the wine will go a long way towards protecting it.

One thing you have mentioned is that the wine is fizzy instead of bubbly. If the wine has re-fermented, most people would describe it as bubbly and not fizzy. The CO2 bubbles from a fermentation are pretty good size. Fizzy sounds like the bubbles are smaller than that. That is what you would expect to find with a bacterial infection.

You also said that it fizzed for a long time. This is fairly definitive. When you get a fizzing that bubbles evenly for a period of time, that is also an indicator of a bacterial infection. Carbonation from a re-fermentation is more explosive and short-lived. A bacterial infection is not explosive. Once you open the bottle, it take a few seconds for it to build up a head of steam and get going.

I’m not sure, because I am not there, but I would guess the reason your homemade wine is fizzy is because of a bacterial infection. That being the case, sanitation of equipment and use of sulfites needs to be the focus when making future batches.

Best Wishes,
Ed Kraus
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Ed Kraus is a 3rd generation home brewer/winemaker and has been an owner of E. C. Kraus since 1999. He has been helping individuals make better wine and beer for over 25 years.

Have now racked my muscadine wine for the 2nd time and gave it a taste test. It seems to have a very tart taste. What can I do to correct this?

Name: Bud
State: Tennessee
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Hello Bud,

The reason your homemade Muscadine wine is too tart is because the acidity is too high. The acidity comes from the fruit, itself, in this case the Muscadine grapes. It can also come from any Acid Blend you added as called for in your wine recipe. Every crop of Muscadines has a little difference in tartness, so it is hard for a homemade wine recipe to be accurate every time. The same goes for making wine with most fruits.

There are some things you can do to reduce wine acidity, but now is not the time to do it. You will want to wait until the wine has completely cleared and is to the point where it could be bottled. Once you are at this point in the wine making process, you can take corrective actions to lower the wine’s acidity.

The best place to start is with an Acid Test Kit. This will tell you how much fruit acid is in the homemade wine and how much should be in it. It’s a great product to use in such a situation. All you need is a small sample of the wine to take a reading, and it’s fairly quick. The reading will tell you exactly how much titratable acid is in the wine and what it should be.

There are three ways to reduce wine acidity and get the wine’s tartness in the right range:

• Dilution:
  If the wine is just a little too tart, you can do something as simple as add water to dilute it. You should use distilled water so that free oxygen from the water is not introduced into your wine. The obvious problem with using this method to lower the acidity of a wine is that it is diluting the wine’s flavor as well. If you have taken a reading with the Acid Test Kit and know what your wine’s acid level is and what it should be, you can use something called a Pearson’s Square to figure out how much water it would take to reach your target acidity level.

• Neutralization:
  One product that is perfect for reducing wine acidity is Acid Reducing Crystals. It is added directly to the wine and neutralizes a portion of the acid causing it to drop out as tartrate crystals. The directions on the side if the jar will tell you exactly how much of the Acid Reducing Crystals to add to reach your target acidity level.

• Malolactic Fermentation:
  A malolactic fermentation is essentially a controlled bacterial fermentation with a selected malolactic bacterial culture. It is something separate from the alcohol fermentation and is usually started at the tail end of a yeast fermentation or later. The malolactic culture slowly ferments malic acid into both lactic acid and CO2 gas. Not only is lactic acid not as tart as malic, there will be less of it when the fermentation is done, by about half. The other half is dissipated from the wine as CO2 gas. Some types of wines are routinely put through a malolactic fermentation for flavor considerations, but not all wines are well suited for a malolactic fermentation. For this reason, you should use malolactic fermentations with caution when used for the sole purpose of reducing wine acidity.

It may be a little obvious at this point, but you can also use a combination of the three methods to lower the acidity of the wine. This is a good option for wines that are way too tart.

If you make wine from fresh fruits for any length of time, eventually you’ll run into a situation where the wine is to tart. Knowing how to reduce wine acidity is key to becoming a well-rounded home winemaker.

Happy Winemaking,
Ed Kraus
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Ed Kraus is a 3rd generation home brewer/winemaker and has been an owner of E. C. Kraus since 1999. He has been helping individuals make better wine and beer for over 25 years.

Degassing the wine has been one of my biggest problems, stirring just does not get it done. I am in the health field so… Next I tried a surgical suction pump generating about 20 inches of mercury neg pressure. That did ok but there is still a little fizz. Next I went for stopcocks, tubing and 60cc syringe, boy can I get negative pressure with that. No more fizz but you should see the bubbles that come out and keep coming out even after the wine taste flat with no fizz. Any idea what I am pulling out, can’t all be CO2 can it?

Name: Bill B
State: NY
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Hello Bill,

Thanks for your great question on how to degas homemade wine. I hope this information clears things up for you.

To answer your question, absolutely there can still be CO2 gas in your homemade wine. At one atmosphere the wine can be completely stable and still have CO2 gas. Then as you apply negative pressure or try degassing the wine with a vacuum, the CO2 bubble begin to appear. The fact is, some CO2 will always want to remain saturated into the wine, just not enough to matter or taste. So I wouldn’t worry about it too much.

As you have suggested, there are also other gases in your homemade wine. They are mostly produced during the fermentation. These are gases such as sulfur dioxide and hydrogen sulfide. Fortunately, these gases are only in trace amounts as compared to the carbon dioxide, but can affect the aroma and flavor if they become excessive.

One item you might want to try in the future for degassing your homemade wines is called The Whip. This is a basically an optimally-shaped rod that is used with a drill. It attaches to a hand-drill just like a drill bit would. It agitates the wine and causes the CO2 gas to nucleate and release as bubbles.

The reason I bring up The Whip is twofold:

1. It will degas your homemade wine without splashing it. This is important because splashing can cause air to saturate into the wine which can promote oxidation if it becomes too excessive.

2. It’s a lot less work. You just stick it into the wine, pull the trigger, and let it do its thing.

It is important to realize that when siphoning, pouring, bottling, or doing whatever to a wine, you will get bubbles, no matter what. This is because, just like most liquids, the wine has surface tension that causes these bubbles to form.

I would suggest to you that if you are to a point that you can not get anymore CO2 bubbles to occur when using an agitation method such as a The Whip, then you are done degassing the wine. While you may be able to get more CO2 from the wine with a vacuum, it is not necessary.

Also, realize that as you go through the steps of making a wine, the act of racking, transferring and bottling will give additional opportunities for the CO2 and other gases to release. What it comes down to, is that degassing homemade wine is not completely necessary until you are ready to bottle it.

Overall, degassing homemade wine is not anything you should worry over too much, Yes, you want to get the bulk of the gas out of the wine. And yes, you want to do it without splashing the wine. But expecting to get every last bit with a vacuum a strong vacuum is not necessary.

Happy Winemaking,
Ed Kraus
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Ed Kraus is a 3rd generation home brewer/winemaker and has been an owner of E. C. Kraus since 1999. He has been helping individuals make better wine and beer for over 25 years.