Stainless Steel Spots: What's The Cause?

Stainless steel pots and pans are a staple in most kitchens. They're durable, non-reactive, and heat up quickly and evenly. However, despite being designed to resist corrosion and rust, they can get burnt-on messes and discolouration.

The most common cause of spots on stainless steel pots and pans is calcium deposits from water. Tap water, even if it's not hard water, tends to contain small amounts of calcium bicarbonate. When water is boiled, the water breaks down the bicarbonate into calcium carbonate, which doesn't dissolve easily in water, oil, or soap and water. This leaves a hazy white residue on the bottom of your pans.

To remove these stains, you can use a commercial cleaner, or a mixture of vinegar and water.

Pitting/Salt Damage

Pitting, also known as salt damage, is a form of rusting that occurs when the protective layer of chromium oxide on the surface of stainless steel starts to break down. This often results in many tiny circular indents across the stainless steel surface.

Causes of Pitting

Pitting is caused by the presence of chlorides, like salt. When undissolved salt is added to a stainless steel pot, or water is boiled dry, the chloride in the salt can attack the passive layer of chromium oxide, leaving pockmarks where it removes the oxide.

Preventing Pitting

To prevent pitting, it is recommended to add salt to water only after it has started boiling. This ensures that the salt dissolves immediately and does not settle at the bottom of the pot. Additionally, it is important to avoid using bleach and other cleaners containing chlorine when cleaning stainless steel cookware.

Repairing Pits

Once pitting occurs, it cannot be repaired. The best strategy is to avoid it by modifying cooking and cleaning habits. However, the chromium in stainless steel will form a new layer of chromium oxide over the pits, making the cookware as corrosion-resistant as before. While pots with pitting are still safe to use and will not affect the performance of the cookware, some people choose to dispose of heavily pitted pots to avoid the increased chance of metals leaching from the cookware.

Calcium Deposits/Water Stains

Calcium deposits, also known as water stains, are those white stains that just won't scrub away. They are caused by the calcium bicarbonate that is present in tap water. When water is boiled or food is cooked in water, the water breaks down the bicarbonate into calcium carbonate (aka chalk or limescale). This is the hazy white stuff that sticks to the bottom of pans.

Calcium carbonate doesn't dissolve easily in water, which is why soap and water will not remove the deposits. It's also not soluble in oil, which is why it remains stuck even after cooking with oil in the pan.

To remove calcium deposits, you can use an acidic solution such as vinegar and water or a product like Bar Keepers Friend (a mild oxalic acid). These products will dissolve the calcium deposits, leaving your stainless steel pans shiny and clean. Simply add 1/3 cup water and 1/3 cup white vinegar to the pan and warm the mixture for a few minutes. Then, discard the liquid, wash, and wipe.

To prevent water stains, always dry pans immediately after washing. You can also prevent water spots by making sure to add salt to the water only after it has started boiling.

Burnt Food

Method 1: Baking Soda and Vinegar

This method combines the use of affordable pantry items that are usually readily available. Here's a step-by-step guide:

• Fill your burnt pan with equal parts water and vinegar.
• Bring the mixture to a boil.
• Add 2 tablespoons of baking soda and remove the pan from the heat.
• Let the mixture soak for up to 15 minutes.
• Discard the liquid and use a sponge or scouring pad to scrub away any remaining burnt-on bits.
• For stubborn spots, apply a paste made of baking soda and a small amount of water. Let it sit for a few minutes before scrubbing again.

Method 2: Lemon and Water

This natural approach uses the power of lemons to tackle burnt food. Here's how:

• Slice two to three lemons and place them in your burnt pan.
• Add enough water to just barely cover the lemons.
• Bring the lemon water to a boil for 5 to 8 minutes.
• Remove the pan from the heat and discard the lemons.
• Rinse the pan with hot, clean water.
• Use a scouring pad or brush to loosen and remove any remaining stuck-on bits.

Method 3: Commercial Cleaners

Commercial cleaners, such as Bar Keepers Friend, are designed to effectively remove burnt food without damaging stainless steel surfaces. Here's a step-by-step process:

• Moisten the pan, making sure to saturate the burnt food.
• Sprinkle the cleaner onto the bottom of the pan to form a paste.
• Scrub the paste into the burnt food with a non-abrasive scrubber or soft cloth.
• Rinse the pan with clean water.
• Repeat the process if necessary.

Method 4: Boiling Water

If you don't have any commercial cleaners on hand, boiling water can be a simple solution. Here's how to do it:

• Begin by scrubbing away as much food as possible with a non-abrasive scrubber.
• Fill the pan with water and add a bit of dish soap.
• Ensure that the stuck-on food is completely submerged.
• Bring the water to a boil and let it simmer for a few minutes.
• Remove the pan from the heat and let it cool.
• Scrape away the loosened food with a spatula.
• Repeat the process if needed or try one of the other techniques mentioned above.

Method 5: Baking Soda and Dish Soap

This method combines the power of baking soda and dish soap to tackle burnt-on gunk. Here's a step-by-step guide:

• Mix 1/2 cup of baking soda, 1/2 cup of warm water, and a tablespoon of dishwashing liquid.
• Allow the cookware to soak for 30 to 60 minutes.
• Scrub the pan with a plastic scrubber, paying close attention to the curves and edges.
• Rinse the pan thoroughly.
• For stubborn residue, make a fresh cleaning solution and heat the pan on the stovetop until it boils.

Additional Tips:

• Always use non-abrasive or "stainless steel-approved" scrubbers to avoid scratching the stainless steel surface, which can make it vulnerable to corrosion.
• Scrub with the grain of the stainless steel, following the polish lines.
• Avoid exposure to chlorides, such as salt, hard water, and chlorinated cleaners, as they can cause pitting and make the surface prone to rust and corrosion.
• Prevent water spots by drying pans immediately after washing.
• To remove water spots, dampen the pan and rub it with a moist sponge and baking soda.
• Avoid cleaning methods that use salt or saltwater, as this can lead to pitting in stainless steel.

Heat Tint/Discoloration

Heat tint or discoloration on stainless steel pans is a common issue, but it's nothing to worry about. It's safe and doesn't affect the performance of the pan or the food cooked in it. It's just proof that you cooked!

Stainless steel is an alloy of metals, including iron, carbon, chromium, and nickel. The chromium in the steel combines with oxygen in the air to form a thin, invisible layer of chromium oxide, which makes the material passive and prevents further reactions with oxygen and rusting. When stainless steel is heated, the oxidation increases, and the top layer becomes thicker. As the layer thickens, the wavelength of light that it reflects changes, and we see a range of colors. As the temperature increases, the oxidation increases, and the colors change, usually from yellowish to blue.

To remove heat tint, you can use a commercial cleaner like Bar Keepers Friend or a mixture of vinegar and water. Simply scrub the area with a soft sponge, rinse, and dry.

Black/Grey Residue

Black or grey residue on new stainless steel cookware is a common issue that many people face. This residue is typically found on the inside of the pan, around the rim, and can be challenging to remove. While it may seem concerning, this residue is usually not harmful and can be safely removed with proper cleaning methods.

This residue is often a result of the manufacturing process, specifically the mechanical polishing process used to create a shiny finish on stainless steel cookware. Sometimes, this process can leave behind a residue that is challenging to remove by hand or in a dishwasher. It is essential to note that this residue is not a sign of low-quality cookware or a defect in the product.

To effectively remove the black or grey residue from your stainless steel cookware, it is recommended to follow these steps:

• Spread a small amount of olive oil on the inside of the pan.
• Let the oil sit for a few minutes.
• Wipe out the excess oil with a paper towel or a clean cloth.
• Wash the pan with dish soap and hot water.

If the above method does not completely remove the residue, you can try an alternative approach:

• Create a mixture of lemon juice and salt.
• Gently scrub the inside of the pan with this mixture using a soft sponge or cloth.
• Wash the pan with dish soap and hot water again.

Some stainless steel cookware manufacturers also recommend gently scrubbing the pan with a mixture of baking soda and warm water (in a 1:1 ratio) before its first use. This step can help remove any residue left over from the manufacturing process and create a protective layer on the pan's surface.

It is important to avoid using harsh chemicals, steel wool, or abrasive cleaners on your stainless steel cookware, as these can damage the surface and make the pan more susceptible to corrosion and residue build-up. Always refer to the care instructions provided by the cookware manufacturer for specific cleaning and maintenance guidelines.

Frequently asked questions