CR-39 Plastic vs Glass Lenses – Battle of the Oldies

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Whenever you go out to buy your glasses, your optician will often ask you if you want plastic or glass lenses. Alright, that isn’t exactly true, not anymore anyway. Today in 2020, plastic and glass lenses aren’t exactly talked about much anymore. Many people believe they have plastic lenses when in reality they actually have polycarbonate lenses or possibly some other plastic polymer such as high-index. Polycarbonate lenses are a type of plastic lens, but not exactly standard plastic.

CR-39 Plastic vs. Glass Lenses

Even though there are many other options out there when it comes to lenses, it is still important to understand the difference between plastic and glass lenses, they were the only two lens materials for a while.

They each also have their own benefits as well, and there are still some people to this day that prefer glass lenses over any other material available today.

If there are people today that STILL want glass lenses then they must have a great benefit that must not be well known. In a day and age where you have polycarbonate and high index materials that provide light and thin lenses what possible reason could there be to get heavy and thick glass lenses?

As far as plastic lens go, even they are losing ground to polycarbonate and high index lenses are still holding their ground quite well. Plastic lenses still make up the majority of lenses in everyone’s eyeglasses today and still is one of the best selling lense material today. Let’s take a look at why these two outdated and old lens materials are still popular even today.

Benefits of CR-39 Plastic Lenses

Glass lenses were the sole lens material before CR-39 plastic lenses entered the fold in 1947. When plastic lenses showed up they were able to offer similar clarity to glass lenses but offered a much safer, more impact resistant, and lightweight lens.

Plastic lenses quickly became the standard lenses that were put in everyone’s eyeglasses. Let’s take a look at some of the benefits.

  • Lightweight – Unlike glass lenses, plastic lenses are much lighter in weight. Even though plastic lenses are thicker in the same prescription, the weight makes a huge difference.
  • Better Photochromic Lenses – Photochromic plastic lenses performed much better than glass photochromic lenses. Plastic lenses that were photochromic were much darker than glass.
  • More Impact Resistant – Although plastic lenses may still shatter when enough force is applied, they are much more impact-resistant than glass lenses. If plastic lenses do shatter, it does not shatter the same way glass does and is not sharp like glass.
  • Accepts Tints – Plastic lenses have the ability to absorb tints. Which makes it a lot more versatile when it comes to getting lenses in different colors and shades.

To this day plastic lenses are still very popular and are still widely used by many people around the world.

The number one benefit of using plastic lenses today is the fact that they are the most inexpensive lens material available.

Benefits of Glass Lenses

Even though glass lenses are not as widely used anymore, glass lenses still hold a couple of benefits. To this day there have been no other materials that have been able to match glass lenses when it comes to clarity, scratch-resistance, and ability to withstand extreme temperatures. Let’s take a look at each of those in detail:

  • Clarity – There is no lens material that can beat glass lenses in clarity. Anyone who has used a polarized pair of sunglasses that are glass lenses understands the difference in optics between a glass and plastic lenses. Looking out of glass lenses look much more clear than plastic lenses.
  • Scratch Resistance – Glass lenses still offer far superior scratch resistance than any other lens out there. Anyone who is in a dusty environment is always advised to get glass lenses due to the scratch-resistant feature alone.
  • Extreme Temperatures – If plastic lenses are kept in extreme temperatures like heat the coatings could potentially get micro-cracks in it or the coatings could separate from the lenses. This is something that does not happen with glass lenses.
  • Thinner – Believe it or not glass lenses are thinner than plastic lenses. The reason why you might not notice is due to the weight of glass lenses.

Disadvantages of CR-39 Plastic Lenses

Even though plastic lenses are very popular, there are still some disadvantages of plastic lenses.

  • Scratches Easy – Plastic lenses have a soft surface that scratches very easily. Even though plastic lenses have a scratch-resistant coating applied when they are made, they are still very vulnerable to scratches.
  • Less Clarity – Plastic lenses offer less clarity than glass lenses. Although the average user might not notice, glass lenses are much clearer.
  • Thicker – Plastic lenses are thicker than glass lenses, however, due to how light they are compared to glass you don’t notice the thickness.

Disadvantages of Glass Lenses

Of course, there has to be a reason why plastic lenses got so popular in the first place. Glass lenses do have some disadvantages as well. Let’s take a look:

  • Shatters Dangerously– Even though plastic lenses have the potential to shatter as well, glass lenses shatter much more dangerously. If glass lenses shatter near your eye, small shards of glass could be very dangerous. This is the reason why glass lenses are not generally put into sports glasses.
  • Frame Choice – Glass lenses can only be mounted into full-framed eyeglass frames. Therefore getting glass lenses limits the styles of frames that you could choose from.
  • Heavy – Glass lenses are heavy, even the thinnest piece of glass is still on the heavy side. People that have sensitive noses generally do not do well with glass lenses. 

Final Thoughts

While glass lenses do offer superior optics and scratch resistance, plastic lenses are overall safer and inexpensive to use. If you are looking for non-prescription sunglasses then maybe a look at the glass lenses might be worthwhile.

With the advances in lens materials though glass lenses may be used less and less. Only time will tell.

What are your thoughts on plastic and glass lenses? Which one do you prefer? Let me know below!

As always thank you all for reading, if you have any questions about this article feel free to leave a comment below. If you have any other general questions feel free to use the contact form to get a hold of me.






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