Photochromic Not Darkening

Why Won’t My Photochromic Lenses Darken?

Photochromic lenses react to several factors, including temperature, UV exposure, and the lens material itself. Certain conditions can affect how dark your lenses become and how quickly they transition:

• Temperature Plays a Role: The performance of photochromic lenses is directly influenced by temperature, and here’s how it works:

  • In Hot Weather: The light-sensitive photochromic molecules react more quickly, causing the lenses to fade back to clear faster. However, this reaction also limits how dark the lenses get, resulting in a lighter tint.

  • In Cold Weather: Cooler temperatures allow the lenses to achieve a darker tint. However, the reaction of the light-sensitive photochromic molecules slows down, so the lenses take longer to return to clear.

• UV Exposure is Key: Photochromic lenses rely on UV light to activate their darkening properties. On cloudy or overcast days, UV rays are still present but at a reduced intensity. Because of this, photochromic lenses will still darken, but not as deeply as they would on a bright, sunny day with direct UV exposure. It’s also important to note that photochromic lenses generally won’t darken indoors or behind most car windshields, as glass blocks the majority of UV rays.

  • The only exception is Transitions® XTRActive® lenses, which will darken up to 53% behind the windshield.

• Designed for Balance: Photochromic lenses aren’t meant to get as dark as traditional sunglasses. Their focus is on providing adaptable, everyday eyewear, balancing clarity indoors and sun protection outdoors.​​​​​​​​​​​​​​​

Do All Photochromic Lenses Darken the Same?

No, different photochromic lenses have varying levels of tint capacity and performance, depending on their design and intended use. Maximum tint capacity is also affected by environmental factors like temperature and intensity of sunlight.​

Here’s a breakdown of approximate maximum tint capacities for some of our photochromic lens options:​​​​​​​​​​​​​​​

• Zenni's Standard Photochromic - Up to 50-70% tint capacity

• Zenni’s Blokz® Photochromic - Up to 50-70% tint capacity

• Transitions Signature® Gen S™ - Up to 70-80% tint capacity

• Transitions® XTRActive Polarized™ - Up to 70-80% tint capacity outdoors

  • Up to 53% tint capacity behind the windshield

  • Up to 90% polarization efficiency in direct sunlight

  • Generally darker than Transitions Signature® Gen S™ under the same conditions​​​​​​​​​​​​​​​

How Can I Test My Photochromic Lenses?

You can easily test if your photochromic lenses are working properly with this simple method:

1. Take your glasses outside on a sunny day (not behind a window or windshield).

2. Place them lens-side up on a piece of white paper in direct sunlight.

3. Wait at least 5 minutes to allow the lenses to darken fully.

This test simulates typical UV exposure and will help you see the maximum tint capacity of your lenses. If your lenses don’t seem to be performing as expected, feel free to contact us! Our team is happy to assist and help troubleshoot any concerns.