Complete Guide to Preventing Yellowing of Figures | Thorough Explanation from Causes to Prevention and Removal Methods

Have you ever experienced your precious figures turning yellow without you noticing? When white or brightly colored figures become yellowed, the appeal of your collection diminishes significantly. The yellowing of figures is primarily caused by three main factors: ultraviolet rays, oil, and heat. However, by knowing the appropriate preventive measures and countermeasures, you can maintain their beautiful condition for a long time.

In this article, we will thoroughly explain everything about yellowing countermeasures, from the mechanisms behind the yellowing of figures to preventive measures using UV-cut cases and LED lighting, as well as removal methods using melamine sponges, baking soda, and hydrogen peroxide. For general maintenance methods for figures, please also refer to the "Complete Guide to Figure Maintenance."

Three Causes of Yellowing in Figures

The yellowing of figures occurs due to chemical changes in the plastic material. Figures made of ABS resin, in particular, tend to yellow easily, and parts that are white or brightly colored are more noticeable. The main causes of yellowing are changes in molecular structure due to ultraviolet rays, the adhesion and oxidation of oils during manufacturing or from handling, and the acceleration of degradation in high-temperature environments.

By understanding these causes, you can take effective preventive measures. Additionally, since the susceptibility to yellowing varies by material, it is also important to know the material of your figures.

Cause 1: Chemical Changes Due to Ultraviolet Rays

Ultraviolet rays are the biggest cause of yellowing in figures. Not only direct sunlight but also ultraviolet rays are emitted from indoor fluorescent lights, and prolonged exposure can change the molecular structure of the plastic.

ABS resin is particularly vulnerable to ultraviolet rays, and when exposed, the molecules break down and produce yellow substances. This chemical change is irreversible, making it difficult to completely restore the altered molecular structure, so prevention is crucial. Figures displayed near windows or directly under fluorescent lights may start to show noticeable yellowing within a few months to a year.

Cause 2: Adhesion and Oxidation of Oils

Oils that adhere to the surface of figures can also oxidize over time, leading to yellowing. The main sources of oil are release agents used during manufacturing (to make it easier to remove from molds), lubricants used in machinery, and sebum from handling.

These oils are initially colorless but gradually discolor to yellow as they react with oxygen in the air. Particularly, new figures may have a lot of release agent remaining, which is why they feel sticky after being unboxed. If left unattended, the oils can solidify on the surface, becoming noticeable as yellowing. Regular cleaning to remove oils is fundamental to preventing yellowing.

Cause 3: Acceleration of Degradation Due to Heat

High-temperature environments accelerate chemical reactions caused by ultraviolet rays and oils. The higher the temperature, the more active the molecular movement of the plastic, speeding up the degradation process.

Environments where summer room temperatures exceed 30 degrees Celsius, near heating appliances, or inside cars are particularly dangerous. The ideal temperature for storing figures is said to be between 20 and 25 degrees Celsius, and environments that significantly exceed this range increase the risk of not only yellowing but also deformation and stickiness. Figures placed near windows are particularly susceptible to both direct sunlight and heat, creating the most conducive conditions for yellowing.

Susceptibility to Yellowing by Material

The susceptibility to yellowing varies greatly depending on the material of the figure. The most prone to yellowing is ABS resin, especially white or brightly colored parts, which show discoloration prominently. PVC figures are less prone to yellowing than ABS resin, but they have a different issue of stickiness due to plasticizers. Figures made of resin or soft vinyl are relatively less prone to yellowing, but they are not completely immune. For any material, avoiding ultraviolet rays and high temperatures is the basic countermeasure.

Seven Preventive Measures to Avoid Yellowing

Once yellowing occurs in figures, it is difficult to completely restore them to their original state. Therefore, preventive measures to avoid yellowing are of utmost importance.

Here, we introduce seven preventive measures that can be implemented immediately, from utilizing UV-cut cases to regular cleaning. By combining these measures, you can keep your precious figures in beautiful condition for a long time. From cost-effective measures to more comprehensive environmental improvements, incorporate them according to your situation.

Preventive Measure 1: Block Ultraviolet Rays with UV-Cut Cases

The most effective way to prevent yellowing from ultraviolet rays is to store figures in cases with UV-cut features. By choosing a case with a UV cut rate of over 99%, you can almost completely block ultraviolet rays coming from indoor fluorescent lights and windows.

Both acrylic and glass cases are available as UV-cut products, but acrylic cases are lighter, easier to handle, and more affordable. However, acrylic is prone to scratches, so it is necessary to use a soft cloth when cleaning. Glass cases are heavier but have the advantage of high transparency and are less likely to become cloudy over long-term use.

The placement of the case is also important; even with a UV-cut case, it should be avoided to place it in direct sunlight by the window. This is because, even if the case can cut ultraviolet rays, it will still be affected by heat.

Recommended UV-Cut Case Selection

When choosing a UV-cut case, check three points: UV cut rate, transparency, and size. An ideal UV cut rate is over 99%, so choose one that is clearly stated on the packaging or product description. If the transparency is low, the figure will not look beautiful.

Sizes vary from large cases that can store multiple figures to compact ones for a single figure. Choosing a case with a back mirror allows you to appreciate the back of the figure as well. Prices range from a few thousand yen to tens of thousands of yen, but considering the long-term protection of the figure, it is worth considering as an initial investment.

Preventive Measure ②: Choosing a Storage Location Away from Direct Sunlight

Even if you do not use a UV-cut case, you can significantly reduce the risk of yellowing just by being creative with the storage location. The most important place to avoid is by the window, as ultraviolet rays can penetrate even with the curtains closed.

Using blackout curtains or UV-cut curtains can help block some ultraviolet rays from the window. The ideal placement for figures is in a cool, dark place, such as against a north-facing wall away from the window or inside a closet. If you cannot change the room layout, applying UV-cut film to the window glass, as mentioned later, is also effective. Additionally, if you display figures on an open shelf, pay attention to the position of the lighting and avoid placing them directly under fluorescent lights.

Preventive Measure ③: Switching to LED Lighting

By switching indoor lighting from fluorescent to LED, you can significantly reduce damage from ultraviolet rays. Fluorescent lights emit ultraviolet rays due to their mechanism, while LEDs emit almost no ultraviolet rays.

LED lighting not only has less ultraviolet light but also generates less heat, reducing the risk of deterioration due to heat. Furthermore, there are economic benefits as they consume less power and have a long lifespan. If you want to spotlight your figures, it is also recommended to use LED bulbs. Choosing a color temperature of around daylight white (about 5000K) will make the colors of the figures appear natural.

Preventive Measure ④: Utilizing UV-Cut Film

If you are concerned about ultraviolet rays from the window, UV-cut film that can be applied to window glass is effective. By choosing a film with a UV cut rate of over 99%, you can significantly prevent yellowing from direct sunlight.

Many films have high transparency, allowing you to cut ultraviolet rays while maintaining the brightness of the room. There are also removable types that can be used in rental properties. They can be purchased for a few thousand yen at home centers or online shops, and you can apply them yourself. If it is difficult to cover the entire window, applying it only to the windows near where the figures are displayed is also a method.

Preventive Measure ⑤: Regular Cleaning to Remove Residual Oils

By regularly removing release agents and sebum that adhere to figures, you can prevent yellowing caused by the oxidation of oils. If you feel stickiness when unboxing a new figure, wash it immediately with neutral detergent and remove the release agent.

For regular cleaning, lightly wiping with a soft microfiber cloth about once a week is effective. Since touching figures with bare hands can leave sebum, it is recommended to use cotton gloves or nitrile gloves when changing or rearranging displays. Gently washing the entire figure with lukewarm water mixed with neutral detergent about once a month will more reliably remove oils. After cleaning, make sure to dry completely before storing.

Preventive Measure ⑥: Avoiding High-Temperature Environments

The ideal storage environment for figures is a temperature of 20 to 25 degrees Celsius and humidity of 40 to 60%. High-temperature environments can cause not only yellowing but also deformation and stickiness, so special attention is needed for temperature management, especially during the summer.

Avoid placing figures near heat-generating devices such as heaters, computers, and televisions. In summer, adjust the room temperature with air conditioning or at least ventilate to prevent heat buildup. It is absolutely essential to avoid leaving figures in a car, as the interior can exceed 60 degrees Celsius in summer, causing significant damage even in a short time.

Precaution 7: Points to Note When Purchasing New Figures

New figures may have a lot of release agent residue from manufacturing. If you feel stickiness upon opening, it is recommended to wash them with water before displaying. When purchasing second-hand items, be sure to check for any yellowing. Figures that have already started to yellow may be difficult to completely stop the progression of yellowing even after taking preventive measures.

How to Remove Already Yellowed Figures

Even if you take precautions, there may be figures that have already yellowed. The appropriate removal method varies depending on the degree of yellowing.

Here, we introduce four removal methods according to the state of yellowing, from mild to severe. Each method requires caution regarding its impact on painted areas, especially in severe yellowing removal, where there is a risk of paint peeling. It is recommended to test on an inconspicuous area first before applying it to the entire figure. While it may not return completely to its original state, choosing the right method can significantly reduce visibility.

Mild Yellowing: Removal with Melamine Sponge

If the surface is only slightly yellowed, it may be possible to remove it with a melamine sponge (such as "Geki-Ochi-kun"). Melamine sponges have a very fine mesh structure and work by polishing away surface dirt and discoloration.

The usage procedure is to first wet the melamine sponge with water and lightly wring it out. Gently rub the yellowed area, being careful not to apply too much pressure. After rubbing, wipe off the moisture with a dry, soft cloth. Since melamine sponges have a polishing effect, rubbing too hard can create fine scratches on the surface, making it appear cloudy. Additionally, do not use it on painted areas as it may peel the paint; use it only on unpainted white plastic parts.

Correct Use of Melamine Sponge

The key point when using a melamine sponge is "not to apply too much pressure." Gently rub as if stroking the surface, checking little by little to see if the yellowing is coming off. Absolutely avoid painted areas and use it only on unpainted parts.

For small parts or areas with uneven surfaces, cutting the melamine sponge into smaller pieces or wrapping it around a cotton swab can make it easier to work with. Instead of rubbing the entire figure at once, it is recommended to test on an inconspicuous area first and then gradually expand the area.

Moderate Yellowing: Removal with Baking Soda Paste

For yellowing that cannot be removed with a melamine sponge, baking soda paste is effective. Baking soda paste is made by adding a small amount of water to baking soda to create a paste, which has a mild polishing effect and helps lift dirt.

To make it, add water gradually to 2 tablespoons of baking soda until it reaches a toothpaste-like consistency. Apply this paste to the yellowed area and gently rub with a soft cloth or toothbrush. Leaving it for about 30 minutes to an hour enhances the effect. After that, rinse thoroughly with lukewarm water and wipe off the moisture with a dry cloth. If rinsing is insufficient, white baking soda residue may remain, so be sure to wash it off carefully. Since baking soda also has a polishing effect, it cannot be used on painted areas.

Severe Yellowing: Bleaching with Hydrogen Peroxide

For severe yellowing that cannot be removed with baking soda, bleaching with hydrogen peroxide is effective. Hydrogen peroxide can be purchased at pharmacies, and a 3% concentration should be used. While it has a strong bleaching effect, it also carries a high risk of damaging paint, so use it only on unpainted parts.

The method is to soak the figure's parts in hydrogen peroxide and place them in a sunny spot for 3 to 6 hours. The chemical reaction between ultraviolet light and hydrogen peroxide breaks down the substances causing yellowing. Regularly check the condition, and when the yellowing has lessened, remove it. After that, rinse thoroughly with running water and allow to dry completely. If it does not become completely white in one go, it can be repeated several times, but always check for any impact on the paint.

Precautions When Using Hydrogen Peroxide

Hydrogen peroxide is a highly effective but also risky method. Using it on painted areas can lead to peeling or discoloration of the paint, so partial testing is essential. Ensure adequate ventilation during the process, and if it comes into contact with skin, wash it off immediately with water. Additionally, hydrogen peroxide is sensitive to light and degrades easily, so it is recommended to use it up quickly after opening.

Overall Dirt: Washing with Neutral Detergent

If the issue is overall dullness or dirt rather than yellowing, washing with a neutral detergent is the safest and most effective method. Dissolve dishwashing neutral detergent in lukewarm water (35-38 degrees Celsius) and soak the figure for 12-24 hours.

After soaking, gently scrub with a soft sponge or toothbrush and rinse thoroughly under running water. It is important to rinse thoroughly to ensure no detergent remains. After wiping off moisture, allow it to air dry away from direct sunlight. This method has the least impact on the paint and is also effective for regular maintenance. However, it does not have a bleaching effect on yellowing itself, so it is suitable for mild yellowing or preventive cleaning.

Do Not Do: NG Actions

There are certain actions that should absolutely be avoided when removing yellowing from figures. First, the use of ethanol or alcohol is strictly prohibited. These can dissolve the paint and degrade the plastic. Soaking in boiling water is also dangerous as it can cause deformation of the figure.

Avoid drying with a hairdryer as well. There is a risk of deformation or discoloration due to heat. Additionally, scrubbing too hard can scratch the surface, resulting in a loss of gloss and a cloudy appearance. Removing yellowing requires patience, but it is important to handle the figure gently without rushing.

Care and Prevention After Yellowing Removal

Even if yellowing is removed, returning the figure to its original environment will cause it to yellow again. By implementing care and preventive measures after removal, you can maintain its beautiful condition for a longer time.

Particularly important are surface protection and improving storage conditions. Since the surface may be worn down during yellowing removal, applying a protective coating can delay further degradation.

Protecting the Surface with a Top Coat

After removing yellowing, especially if polished with a melamine sponge or baking soda, consider using a top coat to protect the surface. By lightly and evenly spraying a model-specific UV-cut top coat (matte or glossy), you can create a protective layer against ultraviolet rays.

When spraying, always do so outdoors or in a well-ventilated area, keeping a distance of 20-30 cm from the figure and applying a thin layer. Spraying too thickly at once can cause whitening (the surface becoming cloudy), so the key is to apply multiple thin layers. However, use caution when applying to painted figures and test on an inconspicuous area before applying to the entire figure.

Implementing Ongoing Preventive Measures

For figures from which yellowing has been removed, future environmental management is particularly important. If possible, transfer them to a UV-cut case and store them in a place that avoids direct sunlight and fluorescent light. Establish a habit of regular cleaning to prevent the accumulation of oils.

Do not forget to manage temperature and humidity, especially in summer, to prevent room temperature from rising too high. By continuing these preventive measures, you can prevent the recurrence of yellowing that has just been removed and enjoy your precious figures in beautiful condition for a long time.

Summary: Prevention is the Most Important for Yellowing Measures

Yellowing of figures is caused by three factors: ultraviolet rays, oils, and heat, but by taking appropriate preventive measures, the risk can be significantly reduced. There are many measures that can be implemented starting today, such as using UV-cut cases, LED lighting, regular cleaning, and proper temperature management.

Figures that have already yellowed may also have the potential for improvement using methods like melamine sponges, baking soda, or hydrogen peroxide. However, since there is a risk of damage to the paint during yellowing removal, it must be done carefully. The most important thing is to prevent yellowing before it occurs.

Three Key Points for Yellowing Prevention

The three key points to keep in mind for yellowing prevention are thorough UV-cut, removal of oils, and proper temperature management. Blocking ultraviolet rays with UV-cut cases, films, and LED lighting, regularly cleaning to remove release agents and sebum, and storing in an environment with a temperature of 20-25 degrees Celsius are fundamental.

By combining these measures, you can minimize the risk of yellowing. Especially for white figures made of ABS resin, preventive measures from the moment of purchase are crucial.

More Detailed Maintenance Information

Figure maintenance is not just about yellowing prevention. By knowing how to deal with various troubles such as color transfer, dust, and stickiness, you can keep your figures in beautiful condition for a longer time.

For detailed maintenance methods for figures, please refer to the "Complete Guide to Figure Maintenance". Let's make continuous care a priority to protect your precious figures.