01 · LENS COATING
The lens substrate and coating can respond differently to heat
The lens substrate and surface coatings are different materials.
Large temperature changes or excessive heat can create thermal stress between layers and reduce coating stability.
The lens substrate and coating layers differ in material and thickness, so they may not expand and contract identically. Excess heat or repeated thermal cycling can increase interlayer stress, but one universal heat limit should not be claimed for all lenses.
02 · ACETATE
Heat can change the shape of acetate frames
Professional fitting may use controlled heat to adjust acetate; excessive heat can therefore also cause unwanted deformation.
Avoid leaving eyewear for long periods in a sealed, hot car.
Acetate can be adjusted with controlled heat, which means carefully applied heat changes its shape; it does not mean the frame tolerates indefinite high-temperature storage. Uneven heating can alter front alignment, width and temple shape, especially with lenses mounted.
03 · PLASTIC FRAME
Heat resistance differs among plastics
TR, PEI and other materials have different thermal properties.
A heat-resistant material does not mean the complete pair of glasses can be left in high heat without risk.
Engineering plastics such as TR-type and PEI-type materials can have different heat resistance, but a trade name alone does not define the finished eyewear. Lenses, hinges, metal cores, paint and adhesives all share the environment, so resin heat resistance is not a guarantee for the assembled product.
04 · METAL FRAME
Metal frames are not immune to every heat-related problem
Even if the metal frame itself tolerates heat relatively well, lenses, coatings, nose pads, paint and bonded parts may still be affected.
Metal frames may resist gross heat deformation better than acetate, but nose pads, finishes, plastic temple tips, bonded parts and lenses still have their own limits. With very hot washing water, the vulnerable component may be the lens coating rather than the metal chassis.
05 · CAR INTERIOR
A sealed vehicle can become very hot
Avoid leaving glasses for long periods on a dashboard or inside a sun-heated vehicle.
A closed vehicle can remain hot for long periods and dashboard areas can become hotter under direct sunlight. Eyewear is better kept in a case away from sun and heat sources than treated as suitable for long-term car storage.
SOLUTION GUIDE
Protecting glasses from heat
Use cool or lukewarm water.
Limit extended exposure to high heat.
Avoid high vehicle temperatures and direct sun.
Protect the whole lens-frame system, not only one material.
GLANOS LENS CHECK
Heat damage is not only a lens issue
Consider the lens, coating, frame and components as one system.
CAUTION
Do not use hot water to remove grease
A mild cleaner with lower-temperature water is safer for routine care.
GLANOS EYEWEAR
There is a reason glasses feel uncomfortable.
heat damage · car interior · acetate deformation · lens coating · eyewear care