September 30, 2022

Why Your Coffee Tastes Metallic & How To Fix It

Clint Doerfler
Clint Doerfler
 | 
Updated: November 16, 2022
       
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Millions of people drink coffee every day, typically an enjoyable experience. But if you find that your coffee tastes metallic, it can quickly spoil the joy. In this article we'll discuss why coffee tastes metallic and a few ways on how to fix it.

Why Might Your Coffee Taste Metallic?

If your coffee tastes metallic, you're probably wondering what the cause could be. Is it the beans? The water? The machine?

There are a few likely causes for this problem, and luckily, you can fix them.

Possible Causes of Metallic Tasting Coffee

  1. High mineral content in your water (hard water)
  2. New equipment (metal ion leaching)
  3. Dirty equipment (limescale accumulation)
  4. Chloride in your water
  5. Over extracted coffee (brewing it too long)
  6. Subpar coffee roasting / cheap coffee
  7. Old (stale) coffee beans
  8. Reaction to food or medication
  9. Reusable filters

High Mineral Content (Hard Water)

Coffee is 99% water, so it makes sense that the quality of the water you use will impact the quality of your coffee. If your water has a high mineral content, it can lead to your coffee tasting metallic.

Water hardness test strips can help you determine the mineral content of your water (the hardness) and whether it's causing your coffee to taste metallic.

If you're uncertain that water hardness is causing the metallic taste, try brewing with bottled spring water or filtered water and see if that fixes it.

If you're already using filtered water and your coffee still tastes metallic, it is likely that high mineral content is not to blame.
Helpful Tip: Avoid using distilled water when brewing your coffee. Distilled water is actually too pure, and contains no minerals. This can actually lead to even worse coffee! The natural minerals in water are essential for properly extracting coffee.
If you'd like to find out more about testing your water's hardness, check out this quick video.

New Equipment (Metal Ion Leaching)

If you just got a new coffee machine or are using it for the first time, it is possible that your coffee tastes metallic from chemicals leaching from your new equipment. This is most common with plastic parts that come into contact with water or hot liquids.

Most manufacturers recommend first brewing a few pots of water (without coffee) through your machine to help remove any residual chemicals from the manufacturing process.

Reference the owner's manual for specific instructions on your machine.

Manufacturers use various types of metals, such as aluminum, copper, or brass, when making parts for coffee machines. If these metals come into contact with your coffee or water, it can definitely cause a metallic taste in your coffee.

To avoid this is, buy from reputable brands and look for coffee pots that are made with glass or high-quality food grade stainless steel. For more info on food grade stainless steel, see this article.

Remember, you usually get what you pay for with coffee pots. If they're super cheap, it's likely made with low-grade materials (metals) that are more prone to leaching.

Dirty Equipment / Limescale Buildup

Another extremely likely cause of a metallic taste in your coffee is limescale buildup. Limescale is a type of mineral deposit that forms on the components inside your coffee machine. The harder your water supply, the quicker limescale builds up.

Limescale can affect the quality of your coffee in a few different ways. First, it can make your coffee taste metallic or bitter. Second, it can clog up your coffee machine and reduce its efficiency.

To remove limescale buildup, regularly descale your coffee machine with a commercial descaling solution or a homemade vinegar solution. Check out cleaning your coffee and espresso machines.

Chloride In Your Water

Chloride is a chemical found in many public water supplies (usually sodium chloride or potassium chloride). While small amounts of chloride are not harmful, too much can give your coffee a salty or metallic taste.

Chloride concentrations of 40 and 60 mg/liter are necessary for the complete purification of water containing large amounts of pollution.

You have the legal right to inquire about the water quality within your municipality. Federal law also requires public water suppliers to provide customers with annual reports of drinking water quality, known as Consumer Confidence Reports.

If you suspect high levels of chloride in your water, you can purchase a chloride test kit and send it in for testing or try using bottled water when brewing coffee.

Over Extraction

If your coffee has a metallic taste, it could be because of over extraction during the brewing process.

Each brewing method you choose (drip coffee, espresso, French press, pour over coffee), all have an optimal grind size, water temperature, coffee-to-water ratio, and brewing time for proper extraction.

If any of these variables are off, it could lead to over extraction (or under extraction), which can lead to off-putting flavors, including a metallic taste, in your coffee.

With Cold Brew Coffee

If you're making cold brew coffee and it tastes metallic, it may be your grind is too fine, your ratio is off, or you're steeping your coffee for too long.

Cold brew coffee requires a much coarser grind than other brewing methods because the grounds are in contact with the water for a much longer period. A finer grind will cause over extraction and may cause a bitter, metallic taste.

Another cause of metallic-tasting cold brew is using hard water. Because the cold brewing procedure does not bring the water anywhere near a boil, as with conventional brewing methods, the minerals that would normally dissipate instead remain.

Boiling water is an excellent way to soften it if you don't have a water softener. The boiling process separates the hard water minerals, such as calcium and magnesium, and leaves them at the bottom of the pot.

To avoid a metallic taste when making cold brew coffee, try using filtered water or boiling your water first. Just be sure to allow your water to cool to room temperature before adding it to your ground coffee.

With Espresso

The most common issue responsible for a metallic taste in espresso is an uneven water flow through the grounds. Known as channeling, this will cause an uneven extraction and result in poor tasting coffee. Channeling is when water flows more quickly through some coffee grounds than others, leaving coffee over-extracted in some areas and under-extracted in others.

Channeling can occur because of several factors, including the type of grinder, uneven distribution, and tamp pressure.

With French Press Coffee

French press coffee is notoriously easy to over extract. This is because the ground coffee is in direct contact with the water for as long as you allow.

The ideal brewing time for French press coffee is around 4 minutes. If you leave the coffee to brew for any longer than this, it can taste bitter (and possibly metallic).

To avoid over extraction when brewing French press coffee, use a coarser grind than you would for drip coffee and stick to the recommended brewing time.

Poorly Roasted Coffee Beans

The metallic or copper taste in coffee can also come from chemical reactions during the roasting process, especially if the beans are over roasted. Different compounds can form during roasting and impart strange flavors into your coffee during brewing. These flavors can become even more apparent when your hot coffee cools down.

If you roast your own coffee beans, monitor them and stop roasting when they reach the desired color.

If you are brewing with darker roasts and can't seem to shake the metallic taste, give a medium or light roast a whirl and see if it helps.

Old (Stale) Coffee Beans

Coffee beans go stale immediately after the roasting process and can quickly taste funky if you don't store them properly.

You should always store your beans in an airtight container and in a cool, dark place to prolong their freshness. If your coffee beans are more than a few weeks old, they may be the culprit behind your coffee's metallic taste.

If you have older stale beans (more than a few weeks old) and don't want them to go to waste, you can use them for making cold brew coffee. I'm uncertain about the science behind it, but the longer brewing time and cold water extraction somehow mutes the unpleasant flavors found in stale beans.

Another good use for stale beans is to use them in your new coffee maker if it's leaching a weird taste. Knowing you'll just be discarding the coffee anyway, you can use the stale ground coffee to help season your new coffee machine and hopefully get rid of that metallic taste.

Medications and Food / Drink Combinations

Some medications can affect the way you taste food and drink, including your cup of coffee.

There's a laundry list of medications and treatments that can alter your sense of taste, most commonly, cancer treatments, antibiotics, and high blood pressure medications.

If you've started taking a new medication and have noticed a change in the way your coffee tastes, this could be the cause.

Certain food and drink combinations can also cause a metallic taste that would otherwise not be present. For example, consider how drinking orange juice after brushing your teeth affects the taste.

If you suspect that a medication or food/drink combination is affecting the way your coffee tastes, talk to your doctor or a registered dietitian to see if there's anything you can do to lessen the effects.

Using Reusable Filters

If you’re using a reusable filter, it could make your coffee taste metallic.

Manufacturers make most reusable filters out of metal, such as stainless steel or aluminum. Even worse, if you're using a cheap, off-brand filter, it could be made with a lower quality metal that's even more prone to leaching a metallic taste.

To avoid this problem, try using a paper filter instead. You can also look for reusable filters that are made of cloth or other materials that won't leach a metallic taste.

How To Eliminate The Metallic Taste In Your Coffee

Here are a few solutions for the issues mentioned above on improving the taste of coffee that has a metallic flavor:

Fixing Water Quality Issues

If you think your coffee tastes metallic because of the water you're using, there are a few things you can try to improve the quality of your water.

Install a Water Filtration System

This is the most effective way to improve the quality of your water, and thus, coffee.

If bottled water fixes your metallic coffee taste problem but you can still taste it when using tap water, it's strongly recommended to install a water filtration system.

A water softener works by extracting calcium and magnesium minerals from water, making it "less hard". This will not only improve the taste of your coffee but will also help prevent limescale buildup in your coffee maker.

There are whole house systems that will filter all the water in your home, or you can find an under-sink system just for your coffee and drinking water. These are small, affordable, and relatively simple to install.

The investment is worth it if you consider the cost of replacing a coffee machine damaged by limescale or being forever-committed to buying bottled water.

Other Water Softening Methods

If you don't want to go the filtration route, there are other ways you can make your coffee taste better by improving the quality of your water.

Boil Your Water

Bring your water to a boil, then let it cool for about 30 seconds before using it to make coffee. This will separate out most of the minerals (mainly calcium and magnesium) that can make coffee taste metallic.

Use Filtered Water from the Store

Buying filtered water by the gallon can be an economic alternative to buying bottled water, but will be a slight inconvenience.

Integrated soft water filters

As far as coffee machines with dedicated water softeners go, De'Longhi is one of the few manufacturers that features a dedicated soft water filter.

Many coffee machines come equipped with a carbon water filter which helps to remove impurities such as chlorine, but they'll do very little in removing the hard water minerals.

Update Your Plumbing

Older homes often used galvanized iron or steel pipes, which can leach a metallic taste into the water. If you think this might be the problem with your tap water, have a plumber come out and look over your plumbing. Pipes will need to be replaced if they're leaching metals into your water supply.

Removing Limescale From Your Coffee Maker

If you use your coffee maker every day, try to descale it once a month. Also, be sure to replace any corroded parts as needed. Limescale can wreak havoc on the efficiency of your coffee maker, as well as impart chemical tastes into your coffee.

To descale coffee makers, fill the reservoir with equal parts of water and vinegar. Run it through a cycle, then rinse the coffee pot and carafe several times with fresh water to remove any residual vinegar taste.

To descale your espresso machine, use the recommended descaling solution and follow the instructions.

A baking soda/water paste also makes a great cleaner for removing limescale from the carafe and other external parts of your coffee pot.

Use High Quality Coffee Beans

If you suspect that the coffee beans you're using are the reason for the metallic coffee flavors, it's time to switch to a higher quality coffee from a reputable source.

Good coffee roasters take great care to source coffee beans that are free from defects. They'll also roast the coffee beans to perfection, which brings out the coffee's natural flavors.

When roasters do their job well, you shouldn't taste any bitterness, astringency, or other off-flavors in your coffee. These flavors can indicate that the coffee beans were poorly roasted or sourced.

Other Food or Drug Reaction: What to Do

If you've noticed a metallic taste in your morning coffee when consuming certain foods or medications, try enjoying your coffee at a different time of the day.

This can help you determine which food or medication is behind the cause. Once you're able to identify the culprit, you can take steps to avoid eating or taking it around the same time as your coffee.

Unfortunately, with certain medications, you may not be able to avoid a metallic coffee taste altogether. Here, consider switching to an alternative beverage such as tea.

That's a Wrap

If you're experiencing a metallic taste in your coffee, don't worry - you're not alone.

In this article, we've outlined several methods that will help you improve the taste of your brewed coffee. Whether it's installing a water filtration system or descaling your coffee machine, we hope these tips helped to take your coffee from "whack" to "back on track".
Clint Doerfler
Clint Doerfler is the founder of Coffee Gear Gurus® and has been obsessed with everything coffee since a very young “growth-stunting” age. He is passionate about helping fellow coffee lovers make amazing coffee at home, no matter what their level of experience.

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