White plastics, which are synthetic materials commonly used in household and electronic products, are found in items such as kitchen containers, light switches, refrigerator handles and shelves, and other electronic devices because of their clean and versatile appearance. However, with prolonged use and exposure to heat, sunlight, grease, or dirt, these plastics often begin to yellow or develop stains, affecting their original bright appearance. 

On the bright side, there are ways to get rid of most of them. There are cases where the yellow color is impossible to remove entirely, for example, if the yellowish tinge appeared due to sun exposure and aging.

Causes of yellowing of white plastic items

Prior to cleaning, it is important that you have an idea about why your plastic surface turns yellow. Some possible reasons include:

1. Direct sunlight and UV rays
2. Heat and oxidation
3. Foods like curry, tomato sauce, or oils
4. Nicotine and/or cigarette smoke exposure
5. Cleaning chemicals reaction
6. Aging of the material

Yellowing of certain types of plastics is due to chemical changes that occur within the material, particularly old plastics that are exposed to UV rays for a prolonged period of time.

How to clean the white plastics

The first step before starting any whitening process is to make sure your plastic item is clean.

Things needed

1. Warm water
2. Dishwashing liquid
3. Soft sponge or cloth

Instruction

1. Soak your plastic object in water mixed with dishwashing liquid.
2. Clean your object with a soft sponge or cloth.
3. Wash off with clean water.
4. Dry your object with a soft cloth.

Yellow stain removal techniques

1. Baking soda paste technique

Baking soda is an effective and relatively safe way to address yellowed plastics. Baking soda acts as a mild abrasive that removes stains without destroying the surface excessively.

How to do it

1. Dilute baking soda in water and create a thick paste.
2. Spread the paste on the stained area.
3. Wait 15-30 minutes.
4. Gently scrub the area with a soft brush or a sponge.
5. Wipe off the stain.

This technique will work great on kitchen utensils and lightly yellowed surfaces.

2. Hydrogen peroxide solution

A hydrogen peroxide solution works best when whitening plastic that has turned yellow because of oxidation and/or UV rays. What Do You Need?

1. 3% hydrogen peroxide
2. Rubber gloves
3. A soft-bristle brush or cloth
4. Natural sunlight or UV light (optional but useful)

Instructions

1. Apply hydrogen peroxide to the plastic surface, or soak the plastic in hydrogen peroxide.
2. Wait for several hours.
3. If possible, put the object in sunlight or UV light for better whitening.
4. Rinse and then let it dry.
5. It is claimed that using the combination of peroxide and sunlight can greatly improve results.

3. White vinegar soak

White vinegar is useful for removing mineral buildup, grease stains, and mild yellowing.

Instructions

1. Mix equal parts white vinegar and warm water.
2. Soak the plastic item for 30 minutes to several hours.
3. Scrub gently and rinse thoroughly.

Vinegar is especially helpful for food containers and hard water stains.

Best method for intense yellow stain removal

In cases of intense yellow stains, it is common practice for people to use the following combination:

1. Baking soda
2. Hydrogen peroxide
3. Sunlight

Common mistakes to avoid

1. Don’t use harsh cleaning methods: Steel wool or scrubbers may cause scratches on plastics.
2. Don’t use too much bleach: Excessive bleach may weaken plastics and cause uneven color changes.
3. Test the solutions: It is always advisable to first test the cleaning solutions on a small and less visible surface.
4. Permanent yellowing issues: If the cause of yellowing is deep ultraviolet degradation or chemical aging, then full restoration may not be possible.

How to prevent white plastics from discoloring 

Prevention is better than a cure. These tips will help you protect your white plastic products:

1. Ensure that plastics are not exposed to the sun’s rays
2. Wash any food item container right after using it
3. Avoid heating plastics to high temperatures
4. Store plastics in cool places
5. Clean any surface to avoid the accumulation of stains
6. Do not use harsh detergents unless required

Conclusion

Yellow stains on white plastics are a frequent occurrence, but they do not necessarily mean that the piece is doomed. The milder the stain, the simpler the solution will be. When it comes to heavily discolored plastics, a combination of hydrogen peroxide treatment and natural sun exposure works best. White plastic products can stay clean, attractive, and bright if properly cleaned and cared for. See other articles about cleaning. 

Source

• How to Clean Yellowed Plastic So It Looks Like New 
• How to Remove a Yellowing Stain from a White Plastic
• 10 Incredible Ways To Remove Stains From Plastic