The Post-Cleaning Puzzle: Why Moisture Appears Between Panes of Glass

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There’s nothing quite like the satisfaction of clean windows, allowing sunlight to pour in and brighten your home. However, for some homeowners, the joy is short-lived when moisture appears between the panes of their double-glazed windows. This issue can be frustrating, as it not only affects the appearance of your windows but can also lead to other problems. Known as “blown glass panes” or “failed sealed units”, this problem can lead to reduced insulation efficiency, impaired visibility, and unsightly window appearance. In this blog post, we will delve into the reasons why moisture appears between panes after cleaning and how to prevent it.

Causes of Moisture Between Blown Glass Panes

Double-glazed windows consist of two layers of glass separated by a spacer bar, creating an insulating gap filled with inert gas, such as argon or krypton. The glass panes are sealed, forming a barrier that prevents moisture and air infiltration. However, over time, the sealant can deteriorate due to various factors:

a. Age: As windows age, the sealant can lose its elasticity, leading to seal failure.

b. Temperature fluctuations: Extreme temperature changes can cause the glass to expand and contract, weakening the seal.

c. Poor installation: Incorrect installation or low-quality materials can result in the premature failure of the seal.

d. Physical damage: Accidental damage, such as a strong impact, can also compromise the seal.

Consequences of Moisture in Blown Glass Panes

When the seal fails, moisture can enter the space between the glass panes, causing a range of problems:

a. Reduced insulation: The presence of moisture compromises the insulating properties of the window, leading to increased energy costs.

b. Foggy or cloudy appearance: Moisture can condense on the glass panes, obstructing visibility and creating an unsightly appearance.

c. Mold and mildew growth: The damp environment can promote mold and mildew growth, posing health risks to occupants.

Solutions for Moisture between Blown Glass Panes

Fortunately, there are several ways to address the problem of moisture between glass panes:

a. Replace the sealed unit: The most effective solution is to replace the entire sealed unit, including the glass panes, spacer bar, and sealant. This ensures the restoration of the window’s insulating properties and eliminates the risk of recurring issues.

b. Defogging: Some companies offer defogging services, which involve drilling small holes in the glass and injecting a cleaning solution to remove the moisture. However, this method does not repair the failed seal, and moisture can re-accumulate over time.

c. DIY solutions: There are DIY kits available for temporary fixes, but these are not recommended as long-term solutions. It is always better to consult with a professional for proper diagnosis and repair.

Moisture between blown glass panes is a common issue that can have significant consequences for homeowners. By understanding the causes, potential problems, and effective solutions, you can make informed decisions on how to address this issue. Remember that consulting with a professional is always the best course of action to ensure a long-lasting and high-quality repair.

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Existing Seal Failure

As mentioned, seals can fail due to age, temperature fluctuations, poor installation, or physical damage. If you notice moisture between the panes after cleaning, it may be an indication that the seals have already failed. In such cases, it’s crucial to address the issue promptly to avoid further complications, as detailed in the “Solutions for Moisture between Blown Glass Panes” section.

Temperature Changes and Condensation

When the temperature inside the glass panes cools down rapidly, moisture in the air can condense on the glass surfaces. When window seals are compromised, they allow ambient air between the panes of glass. The ambient air between the panes of glass is warm and warm air can hold more moisture than cold air. During the cleaning process, the water on the exterior side of the glass may cool down the air between the panes. Because cold air can’t hold as much moisture as warm air, the cold air is forced to release the moisture onto the glass, much like the condensation on the exterior of a cold glass on a warm day.


Moisture appearing between panes of glass after cleaning can be an unwelcome surprise, but understanding the causes can help you prevent it from happening. By addressing any existing seal failures and considering the impact of temperature changes, you can keep your windows looking clean and clear. If you’re uncertain about the cause of the moisture or how to address it, our team at Super Clean is here to help!

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