What causes stains in cups and mugs?

There are three main causes of stains in cups and mugs. Tannin, Caethins, and Calcium. First, let’s look at What they exactly are and how they cause stains:

Tannin

Tea contains a substance known as tannin or tannic acid. Tannin is  a natural organic substance that is yellowish or brownish and bitter tasting.

It is present not only in Black, green or other popular tea drinks but it is also found in some galls, barks, and other plant tissues, consisting of derivatives of gallic acid.

This acid is a kind of natural dye that give’s it’s color and is also used as dye for things like leather hence where it’s color comes from. This natural dye when exposed to the cup will often leave it’s dye on the cup which is where the stain originates from.

Caethins

Another reason which is similar to the first is another chemical compound found in tea is known as caethins.

Caethins is another kind of substance that is found in fresh green teas leaves, apples, berries and cocoa. It also leaves it’s own kind of stain when left in your cup after it sits for a long time.

Calcium

Lastly, it may not even be the tea itself. Sometimes it can be just the water you drink itself. Some water contains a lot of calcium in the form of ‘temporary hardness’.  

Calcium Hydrogen Carbonate also known as Ca(HCO3)2, when heated, the temporary hardness breaks down into calcium carbonate, which is like chalk and water.

These calcium salts can bind with the tannins in the tea and form a kind of scum. These particles float to the top of the tea, and stick to the side of the cup. Which is where you see the dark stains around your cup.

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How to remove stains from a cup

If regular dish detergent does not remove older tannin stains, there are alternative solutions to remove the stains from your cups. These 4 alternatives will be most effective especially if you have white mugs or cups. The steps are as follows:

• Bleach

  

• Step 1 Get a bucket that is big enough to hold your cups.

• Step 2  Fill it with about 2 to 3 caps fill of bleach.Step 3 Get a boiled pot of hot water and pour them in with the bleach.Step 4 Place the cups softly in the bucket remembering not to get get any on your clothes and leave it in for at least 10 minutes or so.Step 5 Take out the cups with rubber gloves and use a small toothbrush to brush out the stain areas.Step 6 Rinse and check. If there is still some stain left, repeat step.

• Salt

  

• Step 1 Pour hot water into the cup.

• Step 2 Pour enough salt for it to absorb the water and leave it in for one to two minutes.

• Step 3 Scrub inside the cup with a wash cloth or sponge.

• Step 4 Use soapy water and wash the salt out of the cup.

• Step 5 Repeat step one if there is still some stains left.

Baking soda:

Step 1 Use warm water and add dish detergent.
Step 2 Pour in and mix baking soda in the water.
Step 3 Pour the solution in the cups and cover over the mugs.
Step 4 Let it sit over night.
Step 5 In the morning, scrub and rinse the cups with soap.

Vinegar

Step 1 Wet the cups with vinegar.
Step 2 Use salt to soak up the vinegar.
Step 3 Spread it around the cup and let it sit for five minutes.
Step 4 Scrub out the cup and rinse.

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