Does Whiskey in a Flask Go Bad?

Does Whiskey in a Flask Go Bad?
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Flasks, specifically ones made from metal, are a common way to carry around a small portion of whiskey and other distilled spirits, and kept either in your coat or at your hip. Flasks have become a common gift for groomsmen, with the most popular flasks made of stainless steel. 

Say you’ve had some whiskey sitting in your flask for a couple of days and decide to drink it. Is it still good? Does it go bad?

Metal or stainless steel flasks are not supposed to be used to store whiskey or any other hard alcohol long-term. The main purpose of flasks is to transport a small amount of whiskey just enough for drinking over a short time, no more than a few days. These flasks can change the flavor of whiskey, some saying it tastes metallic; it can also discolor the whiskey, diminishing its quality.

Storing of Whiskey in a Flask 

Some stainless steel flasks come with a disclaimer, clearly stating that alcohol should not be kept for long periods and that certain drinks should not be kept in the flask altogether.

For example, some stainless steel flasks will state outright, “It should not be used for beverages with an acid content, such as fruit juices and cordials.” It also says, “Do not keep alcohol in the flask longer than a period of 3 days.” Searching through other stainless steel flasks, many have that same warning.

If left for a long time, say over a week, a metal flask will discolor the whiskey, turning it into a dark greyish color. If kept over 3 days, whiskey can start picking up a metallic taste. 

Flask quality, material, environmental factors, and tightness of seal can vastly affect the quality of the whiskey. 

In general heat, such as from direct sunlight or baking inside a hot car, is also a factor that will significantly diminish the quality of the whiskey. So even for a short period, the flask should be kept in a cool and dark place.

If the seal isn’t tight enough and the flask gets warm, it can speed up the oxidation process of the whiskey. Also, both of these environmental factors cause the whiskey to expand and evaporate, making it weaker as well as changing its color and flavor.

Suggested reading: Will Bourbon Barrels Rot (and How to Preserve Them).

Types of Flasks

There are many types of flasks. Besides stainless steel, there is also pewter, titanium, and glass. Some are even encased in leather. Flasks also come in many sizes, from 3 ounces to 10 ounces, with 8-ounce flasks being the standard. One shot of whiskey is about 1.5 ounces.

Stainless steel flasks

Stainless steel, which comes in different levels of quality, is the most popular material for flasks. It is pretty resistant to corrosion and developing rust but people have reported that rust can still develop on stainless steel flasks.

You don’t want to drink anything out of a rusty flask, and probably best to throw the whole thing out. But there are some ways to clean the rust with chemical cleaners to restore the flask to normal. Keep reading for tips on how to clean a flask.

Stainless steel flasks are timeless, and great because they provide a sense of tradition.

Pewter flasks

Pewter is a softer metal compared to stainless steel that is made up of tin, copper, and antimony. People have said that pewter flasks don’t leave as much of a metallic taste compared to stainless steel if the whiskey is left inside long. Older antique pewter flasks may have lead, while modern flasks are completely lead-free.

Many pewter flasks, such as the English Pewter Company 6oz Pewter Hip Flask with Luxury Brown Leather Pouch are handmade. Also, while stainless steel flasks can be dishwasher safe, pewter flasks are not.

Titanium flasks

Stronger than steel, titanium flasks are anti-corrosive. Titanium itself is extremely durable and also very lightweight. A highly rated titanium flask is the Snow Peak Titanium Flask. According to the product description, “Titanium is one of the lightest, strongest metals on earth and very inert making it one of the best metals for flasks. It produces no off metallic flavors preserving the taste of any scotch or whiskey.” 

Here’s an interesting take from an Amazon reviewer ‘johnjorg.’ “The Snow Peak medium hip flask holds five (5) fluid ounces. BTW, as a test, I put 5 oz. (measured) of 100 proof vodka in it and left it for a month which was up last week. I could taste and smell no off-flavors, and the cap did not leak.” 

Glass flasks

What about glass pocket flasks? Some of these flasks have a white stopper with a wire bail closure so that the seal is airtight. Others will have a cork, similar to a whiskey bottle.

Compared to metal flasks, these types of flasks keep your whiskey better than stainless steel since it is in the same material as the original bottle. Some glass flasks have innovative designs that use break-resistant glass.

There are also glass flasks that can be personalized, making them a great gift for groomsmen.

Price of Flasks

Prices for flasks can vary greatly. The cost of a stainless steel flask can range from $10-$30. The range for a pewter flask is $50-$100. Titanium flasks run from $30-$170. And a glass flask on Amazon generally costs less than $10. There are also plenty of specialty online stores that make and sell their flasks.

Will Certain Alcoholic Beverages Store Better in a Flask?

Liquors with 80 proof and above can be kept in a flask for short periods with no problem. This includes whiskey, rum, vodka, and gin.

However, don’t keep other drinks that have lower alcohol levels, like beer or wine, in a flask. And as mentioned above, mixed alcoholic drinks, carbonated beverages, citrus-flavored, and cream-based liquids should not be kept in metal flasks either. The reason for this is because they could pick up the metallic flavors quicker than higher proof alcohol and even destroy or stain the flask itself.

Recommended article: Does Whiskey Age in the Bottle?

How to Clean a Whiskey Flask

There are different ways to clean a metal flask. Here is one way to clean the flask step-by-step:

  1. Rinse the flask out with water. Make sure any residual alcohol does not sit in the flask for more than 3 days.
  2. Use soap and water to thoroughly clean the inside and outside of the flask.
  3. Add water inside, put the cap on the flask, and shake for additional cleaning.
  4. Rinse the flask with warm water.
  5. Towel dry then place the flask on its side with the cap off and let it air dry.

Long-Term Storage? Forget the Flask!

The real truth is that the best place to store whiskey is in the original bottle or even inside a decanter in a cool dark place that is out of direct sunlight. An unopened bottle of whiskey will not go bad and pretty much last forever. A bottle of opened whiskey is at its best quality for about a year or so, but won’t significantly lose any flavor for many years to come.

Whiskey should be stored at room temperature. But some people will say that 55-60 degrees is the best temperature.

Final Round

There are a lot of flask options to hold whiskey, the popular one being stainless steel. But as most people will testify, these metal flasks won’t hold alcoholic beverages long without affecting the taste and the quality. Metal flasks are best for keeping flavor for short periods and should be used as such. However, alternatives like glass or titanium may be a nifty workaround that will keep your whiskey fresher for longer.

Keep in mind that because of certain laws in the U.S., flasks containing alcohol in public areas are illegal due to open container laws.

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