Selecting and using anti-fog lenses
Anti-fog lenses, we’ve all been there!
That is, entering a warm room from the cold only to find that our glasses instantly fog up. Suddenly we’re either lurching around unable to see clearly or stopped dead, as we desperately search for that lens cleaning cloth.
When it happens to others, it might be a source of amusement and perhaps that applies also at times when we’re the sufferer. However, on the whole, it isn’t funny. In fact, it can be highly annoying and even at times, possibly dangerous. The solution is simple – anti-fog lenses.
Why fogging happens
Typically, if you expose cold glass suddenly to a temperature that’s a lot warmer, then condensation will try to form on the glass via natural physical processes.
Short of changing the laws of physics, there’s not a lot you can do about the basis of this problem. It is going to at least try to happen. Your only hope is to find something that stops that condensation from forming.
Before looking at high-tech solutions, for the sake of completeness we need to consider some DIY-type solutions that have been around for a LONG time:
- washing your lenses with soap then rinsing/drying;
- as per the above but using shaving foam;
- spitting on the lenses before drying off (an old diver’s trick).
There are many others in the same vein.
All these solutions ‘sort of’ work ‘a bit’. They operate by leaving an oily residue on the surface of the lens. That then reduces the ease with which water droplets can form from the air and adhere to the surface. The lenses then stay a little clearer in fogging conditions.
There are some problems with these approaches though:
- they’re not always effective or reliable. Most of us would prefer to have success criteria other than ‘works a bit’ or ‘sort of works’ in most personal and especially professional situations;
- practicality can be an issue – as squirting shaving foam around and spitting aren’t usually considered to be socially gracious ways of entering a room!
Origins of anti-fog lenses
Back in the mid-1960s, Nasa’s GEMINI program encountered this problem in a major fashion when astronauts started leaving their space capsules for the first time.
They quickly developed a coating that could be applied to the visors of space suits, preventing fogging.
Since then, the technology has moved on considerably and has been applied to ordinary glasses of all types.
How they work - different approaches
It’s necessary to consider a little science here:
- hydrophilic molecules essentially bond to water molecules, changing their structure;
- hydrophobic molecules do exactly the opposite – they repel water.
Strange as it may sound, anti-fog lens coatings might use either approach because ultimately the overall effect on your glasses is the same – they stop water molecules forming on the glass lens.
Hydrophilic coatings bond with the water molecules and stop droplets from forming (i.e., the fogging mist). By contrast, hydrophobic solutions push the water molecules away from the glass towards the frame edges where they don’t cause fogging.
Both approaches have their advocates and work well – depending upon certain factors.
The pros and cons can be a little complex, so rather than go into a lot of detail here, please feel free to contact us through our website with your questions.
Coated lenses versus clothes, wipes, and sprays
We regularly get questions on this subject and here is our summary;
- in our view, the best solution by far is to opt for lenses that have a permanent lens-bonded anti-fogging coating. The extra cost for this is usually modest in the context of the best eyeglasses, Vancouver or elsewhere;
- cloths, wipes, and sprays work fine (though some are more effective than others) but the big problem is first that their effects are temporary and secondly, their protection can be removed by some forms of cleaning and other environmental factors;
- cloths and sprays just aren’t always convenient and they can be doubly inconvenient if you realize you’ve left home and forgotten yours.
Our spectacles will if treated sensibly, last for many years given they’re amongst the very best eyeglasses. Vancouver or elsewhere, their quality shines through.
That applies also to permanent bonded anti-fogging solutions. Even so, if you mistreat glasses, for example by cleaning with unapproved substances, you may cause damage to the anti-fogging layer.
Once again, our team at Eyetician will be more than happy to offer further advice and guidance on that subject if you contact us through our website.