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Can a window regain its original shape after being deformed by the sun? In this article, we will look at this issue in more detail and discuss some key topics, such as what causes the warping of windows, how to diagnose the problem, and how to remove deformation caused by sunlight.

smiling woman and windows

Why do windows warp?

Windows made of PVC have the natural ability to deform. This phenomenon is due to the characteristics of the material itself – polyvinyl chloride. In the production of profiles, PVC is extruded at 230 degrees Celsius. During this process, the PVC molecules are expanding.

When the PVC profile is extruded, it is rapidly cooled just after leaving the mold to a temperature of around 40 degrees Celsius. This cooling fixes the structure of the molecules in their expanded state, leading to a permanent profile shape.

However, when PVC is exposed to heat, such as from the sun, its temperature can rise between 60 and 70 degrees Celsius. In this situation, the PVC particles set about to return to their original state through the surface crystallization process. In other words, the heat causes the PVC particles to shrink and take on their natural shape.

Heat causes PVC windows to deform, which can be observed especially in hot weather conditions.

How to check if a window is deformed?

You can perform simple tests and observations to determine if the window is warped. Here are some steps you can take.

1. Half-close method: After closing the window, if the handle remains in the half-closed position and the window cannot be closed all the way, it may indicate warping. Because of deformation, the sash cannot close completely. 

2. Bounce method: If we want to check if the window is deformed, we can open the sash in the open position without lifting it. Gently turn the handle to avoid a complete opening. When we move the window sash, if it “jumps” or does not open smoothly, this may indicate that the window is warped.

3. Thread and Ruler Method: This method involves sticking a thread with tape to the top and bottom of the window. Then, using a ruler, we can measure the distance between the string and the window surface at various points. That will help us estimate the possible deformation of the window.

4. Level and ruler measurements: We can also use a spirit level to check if the window is warped. On the outside of the window, we put the spirit level along the vertical profile, and then we put the ruler in the middle part of the sash. That action allows us to judge whether there is any deformation by measuring the distance difference between them.

5. Tightness check: Close the window and check its tightness. A warped window can have sealing problems, which can cause air or water leaks.

If you are in doubt about the condition of your window, especially if warping is suspected, it is worth consulting a professional who can carry out a more thorough assessment.

What’s next? How to solve such a problem?

There is a tool that can be the key to repairing warped windows – we are talking about an electrical strip for straightening windows. This device has the ability to restore the original shape of windows that have become deformed. You can see how it looks below. ↓

electrical strip for warped windows

How does such an electrical strip work?

Appropriate adjustment of the temperature and time on the electrical strip allows us to release the “thermal shrinkage” on the inside of the profile, which results in the straightening of the profile. The crystallization of the surface occurs only once on a given profile geometry, which ensures that there will be no deflection again.
This process is non-intrusive as it does not require the entire window or door frame disassembly. It is an effective straightening method, which guarantees a 100% removal of deformations and restores the original frame shape.
Below is an instructional video with english subtitles that shows in more detail how such a strip works.



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