Causes of White Frost-Like Substance on the Water-Soluble Film of Laundry Detergent Pods

I. Most Common Cause: Precipitation of Humectants/Small Molecule Substances Due to Environmental Temperature and Humidity Changes

• Precipitation at low temperatures: If the detergent pods are stored long-term in a low-temperature environment (e.g., a balcony in winter, near a refrigerator, with temperatures below 5°C), the solubility of humectants (e.g., sorbitol) dissolved in the film will decrease significantly. When it exceeds the solubility limit, the humectants will precipitate on the film surface as "white needle-like or powdery crystals", resembling a layer of frost. This is particularly common in northern winters and is a typical physical change, not a sign of component deterioration.
• Precipitation due to air-drying in low humidity: If the pod package is not sealed promptly after opening and exposed to a dry environment (e.g., an air-conditioned room, a heated room with humidity below 30%), moisture in the film will evaporate rapidly. This increases the concentration of small-molecule substances (e.g., trace sodium citrate, salts) originally dissolved in water, eventually leading to "supersaturation and precipitation" and forming a white powdery substance on the film surface. For example, pods left uncovered for several weeks after opening often develop this issue.

II. Secondary Cause: Uneven Component Distribution or Slight Migration During Production/Storage

• Uneven mixing during production: If the film raw materials (PVA resin, humectants, plasticizers) are not fully mixed uniformly during melting and blending, local areas may have a higher concentration of humectants or small-molecule substances. During storage, these high-concentration components will slowly "migrate" to the film surface, eventually accumulating and precipitating to form spotty or flaky white frost.
• Slight "blooming" on the film surface: To improve the solubility or stability of the film, some pods are coated with an extremely thin "solubility-aiding coating" (e.g., a small amount of water-soluble resin or electrolyte) on the film surface. If the storage temperature fluctuates significantly (e.g., repeatedly moving pods from the balcony to indoors), substances in the coating may precipitate due to solubility changes, forming white frost. This usually occurs in specific areas of the film (e.g., edges, folds).

III. Situations to Rule Out: Not "Deterioration", But "Abnormal Conditions" Require Attention

• Normal white frost: When gently wiped with a finger, the white substance can be removed. The film itself remains soft and flexible, with no unusual odors (e.g., sourness, mustiness), and there is no leakage or caking inside the pod. In this case, simply wipe the surface clean and place the pod in the washing machine as usual. It will dissolve without residue and will not affect cleaning performance.
• Signs of deterioration: If the frost is accompanied by the following conditions, the pod may have deteriorated and should not be used: ① The film becomes abnormally hard and brittle, breaking when squeezed; ② The detergent inside leaks, making the film surface sticky; ③ There is an unusual odor (e.g., a rancid smell). This is mostly caused by long-term storage in high-temperature and high-humidity environments (e.g., a bathroom), leading to film degradation or deterioration of internal components.

Summary: Nature of the Frost and Handling Recommendations

• Nature: Over 90% of white frost is caused by physical precipitation of components due to fluctuations in environmental temperature and humidity. It is a common phenomenon during pod storage, not a product quality issue, and does not affect cleaning power.
• Handling Recommendations:
  1. If only white frost is present (no unusual odors or leakage), wipe the surface clean with a dry cloth and use it normally.
  2. For subsequent storage, ensure "sealing + room temperature + cool and dry conditions". Avoid long-term storage on balconies, in bathrooms, or near direct air conditioning. Use the pods as soon as possible after opening (preferably within 1-2 months) to reduce the impact of temperature and humidity on the film.