How Sunglasses Are Made - The Parts That Actually Matter
Pick up a pair of sunglasses and they feel like one simple thing. But there's actually quite a bit going on - frames, lenses, hinges, coatings, and a few hidden bits most people never think about. Understanding how it all comes together makes it a lot easier to appreciate what you're actually getting when you buy a pair, especially when you're up against the New Zealand sun day after day.
The process is a mix of industrial manufacturing and careful hand assembly. Luxury brands like to make a big deal about their production methods, but for well-made, affordable eyewear - like what you'll find at iPOP - it's really about getting the fundamentals right: solid construction, reliable protection, and something that'll last.
It All Starts with the Frame
Most everyday frames are made from either plastic or a metal alloy. With plastic, there are two main approaches. The first is injection moulding - melted plastic gets pushed into a shaped cavity, producing lightweight, flexible frames that can take on just about any shape. The second involves cutting frames from solid sheets of acetate, a plant-based plastic that produces richer colours and those classic patterns like tortoiseshell. Once the shapes are cut, the frames go into barrels filled with small wooden chips and polishing paste, tumbling away for several days until they come out smooth and glossy.
Metal frames take a different route entirely. Materials like Monel, nickel, or stainless steel start as long reels of wire that get fed into machines and shaped into the eye wires holding the lenses. Those pieces are then soldered together at high heat to form the bridge and the arm attachments. After that comes plating or painting - your classic gold, silver, or matte black finishes. The balancing act is always the same: strong enough to hold its shape, light enough to sit comfortably on your face for hours.
Why TR90 Is Worth Knowing About
TR90 -short for Tough Resin 90 - is a thermoplastic that doesn't get talked about enough. One of the first things people notice about TR90 frames is how light they are. The second thing they notice is that they don't snap when life gets a bit rough with them.
TR90 has a natural flexibility that lets it bend rather than break. Drop them, toss them in a bag, accidentally sit on them - they're far more likely to bounce back than most frame materials. For anyone with an active lifestyle (which, let's be honest, is most people in Nelson), that kind of resilience makes a real difference over time.
The Hinge - Small Part, Big Impact
The hinge is the only moving part on a pair of sunglasses, and it's easy to overlook until it fails. Standard barrel hinges are the most common - interlocking metal loops held together by a tiny screw. They're reliable, and if the screw works loose over time, they're straightforward to fix.
Spring hinges are the other popular option, particularly for active use. A small internal spring lets the arms flex beyond ninety degrees, which gives a bit of extra forgiveness for different head sizes and means the frames are less likely to snap under pressure. If you've ever worn glasses that dug into the sides of your head, a spring hinge would have sorted that out.
The Lens - Where the Real Work Happens
The lens is arguably the most important part of the whole thing. Most quality, affordable sunglasses use polycarbonate rather than glass - and for good reason. Polycarbonate is incredibly impact-resistant (it's the same material used in bulletproof glass), lightweight, and holds up well to the kind of wear that comes with everyday use. Acrylic is another option, though generally a step below polycarbonate in durability.
Lenses are cut from larger blanks to fit each frame shape, then treated with coatings before assembly. The most important of these is the UV400 filter, which blocks 100% of UVA and UVB rays. Every pair at iPOP has UV400 protection - including all our polarised frames.
Beyond UV protection, lenses can be finished in different ways depending on their purpose. Mirror coatings - like the Revo finishes you see on sporty styles - are created by applying thin layers of metallic oxides to the lens surface. They reflect extra light away from the eye, which is genuinely useful on the water or snow. Gradient tints, where the lens is darker at the top and fades lighter toward the bottom, are great for driving — they handle the overhead glare while keeping your view of the dashboard clear.
The Hidden Skeleton: Inner Core Wire
Most people never know this exists until they notice that one pair of sunglasses keeps its shape for years while another goes floppy after a few months. The difference is often an inner core wire - a thin stainless steel rod embedded inside the arms of the frame.
At iPOP, we include inner core wire in many of our frames, and it's a standout feature of our Sunpro sunglasses. That steel rod gives the frame "shape memory" - the arms won't warp sitting in a hot car, and they won't gradually loosen up with regular use. It also means you can make small manual adjustments to the fit, which isn't possible with frames that have no internal reinforcement.
Putting It All Together
Once the frames are polished and the lenses are ready, assembly begins - and a lot of it is done by hand. Metal frames have a small screw in the eye wire that gets loosened so the lens can be seated in its groove, then tightened back up. Plastic frames are gently warmed to make them slightly pliable, so the lens can be snapped cleanly into place without gaps or rattling. It's careful work, and when it's done right, you won't notice it at all - which is exactly the point.
Branding - How Sunglasses Got Their Identity
The final stage is branding. Back in the 1960s, logos were subtle - tucked on the inside of the arms where only the wearer would see them. As fashion evolved, branding moved outward. Today you'll typically find a brand name on the outside of the temples, the top corner of the right lens, and inside the arms. iPOP keeps it simple: logo on the outside of the left temple.
Logos can be applied a few different ways. Pad printing - where a silicone pad transfers ink onto the surface - is common for affordable frames. More durable options include laser engraving or inlaid metal plaques. On the inside of the arms you'll also see a string of numbers and letters that aren't random. They give you the frame measurements, colour code, and lens filter category.
Branding also changed how people thought about sunglasses. Once just a practical tool, they became a kind of "affordable luxury" - a way to tap into a style or aesthetic without the price tag of a designer bag or high-end suit. But at iPOP, the logo is secondary. What matters is whether the hinges work properly, whether the UV protection is real, and whether the frame is built to last. A good pair of sunglasses performs - regardless of what's printed on the side.
Quality Control: The Last Check
Before any pair leaves production, it goes through quality checks - frame alignment, hinge movement, lens clarity, and UV protection levels. In New Zealand especially, that last one isn't optional. Our UV index is among the highest in the world, and a pair of sunglasses that looks great but cuts corners on lens quality won't protect your eyes when it counts. Getting all of this right is the whole job.
From raw plastic pellets or a reel of metal wire to something you put on your face every morning - it's a more involved process than most people realise. Every component plays a part: a solid hinge keeps the arms from wobbling, a well-built frame sits comfortably without pinching, and a quality lens actually does what it's supposed to do. At iPOP eyewear, that's where the focus stays - on the components that matter, not the markup. Check out all our iPOP blogs for more.
