Adhesion Matters - Adhesives for Watchmaking

Episode Date: August 5, 2025

This episode of Adhesion Matters examines the indispensable and evolving role of advanced adhesive technologies in the watchmaking industry. Historically, watchmaking relied on mechanical fastening and natural glues like shellac. However, driven by demands for thinner profiles, lighter materials, enhanced water resistance, and integrated electronics (especially in smartwatches), the industry has significantly transitioned to synthetic adhesives. These modern chemical compounds offer superior sealing, the ability to bond dissimilar materials, even stress distribution, and design flexibility that mechanical fasteners cannot match.  Key adhesive chemistries employed include epoxies (for structural bonding and jewel setting), silicones (for case sealing, electronics protection, and vibration damping), polyurethanes (for structural and waterproof sealing), cyanoacrylates (for rapid assembly), and UV-curable adhesives (for precise crystal bonding). Specialized products like threadlockers, dial adhesives, and surface modification coatings further enhance performance.  While offering significant advantages in design, performance, and manufacturing efficiency, adhesive bonding presents challenges, particularly regarding meticulous surface preparation, controlled curing, long-term durability under environmental stress, and the critical issue of repairability and recyclability due to the permanent nature of many modern bonds. This tension between performance and sustainability will shape future adhesive innovations in horology.

What if the true unsung hero of a watch isn't its intricate gears, its sparkling jewels, or even its precision movement? What if it's something you can't even see? Something that's fundamentally changed how they're made and how we interact with them. Today we're talking about glue. Seriously, welcome to the deep dive. You're ready to join us as we peel back the layers, pun absolutely intended on the hidden world of adhesives and watchmaking.

We're going to use the material you've shared to uncover how glues, sealants, bonding agents, how they've become utterly indispensable to modern timepieces will trace their journey, you know, from humble beginnings right up to some truly cutting-edge applications. Yeah, and what's really fascinating here is how something so, well, seemingly simple as glue, has profoundly reshaped an industry, an industry long-renowned for its mechanical precision, its intricate craftsmanship. It really is a journey from traditional artistry to high-tech manufacturing. Exactly. And by the end of this deep dive, you'll have a shortcut to understanding the, let's call them, sticky secrets of watch design, a surprising history you probably never expected, the diverse chemistries at play and some really interesting tradeoffs between durability and, well, repairability. You'll gain a whole new appreciation, I think, for how the watch on your wrist is actually built. Okay, let's unpack this then. Why the shift?

From traditional mechanical fasteners, screws and things, to adhesives. When I think of watches, I immediately picture tiny screws, springs, not, well, not glue. What drove that fundamental change? That's a great question. And it really comes down to a couple of things. Evolving consumer demand and new technological capabilities. People now want watches with thinner profiles, lighter materials, much better water resistance, and, of course, the seamless integration of complex electronics, especially, you know, with the rise of smartwatches.

Mechanical fasteners with their bulk, their limitations. They just couldn't keep up with these demands without compromising the design or performance. Right, they take up space. Exactly. And modern adhesives offer solutions that traditional mechanical fasteners simply can't. They enable truly seamless joints, provide superior ceiling, better protection from the elements. And crucially, they allow manufacturers to bond completely to similar materials. Think metal to glass or plastic to composite. You can do that without compromising structural integrity or adding significant bulk.

So it's not just about ditching the screws. Not at all. It's about pushing the very limits of what a watch can be. How thin, how waterproof, how integrated it can become. Adhesives really unlocked an entirely new design language. They're critical for achieving the performance, the longevity, and the sleek aesthetics we expect today. It's wild to think about how far back this idea of glue goes, though. Even before anyone was dreaming of telling time with a tiny machine on their wrist, the history here is far deeper than I ever imagine.

Oh, it's astounding. We're talking maybe 200,000 years ago, Neanderthals using birch bark tar. Birch bark tar. For what? To haft stone tools, basically, sticking the stone head onto a handle. Wow. Then fast forward, you've got ancient civilizations. The Egyptians, maybe 1,500 to 1,000 BC, using animal glue for wood bonding.

You can see it into Tocamoon's coffin and the Romans, the Greeks. They refined animal and fish glues, even adding things like egg whites, blood, Even cheese, apparently. Seriously. Seems so. So the basic idea, the understanding of adhesive properties for precision, for durability, has been around a very, very long time, long before watchmaking as we know it. But when did it really make its proper horological debut?

I'm picturing some old school watchmaker hunched over a bench, pulling out a pot of shalak, was it? You're absolutely right, shalak. It's a natural polymer actually secreted by the lackbug. It was historically really significant in watchmaking. its key property, it's thermoplastic, melts at a relatively low temperature around 75 degrees C. Okay, so it melts easily. Why was that useful? It allowed watchmakers to secure pallets, those little jewels on the lever plate. They could gently heat the lever, soften the shellac, then make incredibly precise, tiny adjustments to the pallets, and then just let it cool to harden.

It fixed the jewels firmly in place. It was also used temporarily sometimes for holding components or tools during work. Ah, I see. And the crucial point, I guess, was that you could undo it. Exactly. It's reversibility. You could undo it with heat, which allowed for future repairs or adjustments. That was vital for traditional watchmaking. So that reversibility was key for shellac. Makes you wonder if modern watchmakers sometimes wish they had that easy undo button with all the permanent glues we'll get to.

Huh. That's a fantastic point. And yes, it touches on the challenges we'll discuss later. But for now, let's move from ancient glues and shellac into the modern era. what really kicked off the synthetic revolution in watchmaking adhesives. Well, speaking of synthetics, I came across something called GS hypocement. That sounds pretty specific. What made that particular adhesive such a sort of pivotal moment? It absolutely was. GS hypo cement, invented back in 1939, was specifically formulated for watchmaking.

That was the key. It came with a very fine precision applicator. It dried clear, medium strength. Crucially, it wouldn't damage delicate surfaces like plastic watch crystals. So it became ideal for bonding those plastic glasses, bezzles, little metal parts. What made it stand out. What truly distinguished it was its controlled setting time.

It got tacky in about 10, 15 seconds vital for making tiny adjustments. Then it dried in maybe 10, 15 minutes, and was fully hardened after about an hour. That controlled timing was essential for delicate assembly work. You had a window to work. Right, not instant, but not hours either. Precisely. And soon after, you get cyanoechrolates, what most people call super glue. Their introduction offered extremely rapid bonding, which opened up even more possibilities for assembly, especially for small, quick fixes.

This historical overview really sets the stage. But the real strategic pivot, the moment glue changed, not just how watches were made, but maybe how we think about owning them. That seems to be exemplified by the swatch skin family, right? This wasn't just about making a watch thinner. It was about rethinking the whole product lifecycle. That's absolutely right. The swatch skin family, introduced in 1997, is the perfect case study here. In these watches, the movement is permanently sealed inside the case.

They use a structural adhesive that secures both the acrylic crystal on the front and the case back. Permanently sealed so you can't get into it. Exactly. The consequence of this design is, as the source is state, the timepiece becomes invulnerable to environmental conditions, moisture, dust, whatever. But the flip side, and this is crucial, is that they are rendered maintenance-free, i.e., impossible to service. No, impossible to service. That's a big shift. It's huge.

The shift fundamentally prioritized, robust sealed units, and frankly, cost-effective mass production over the traditional model of repairability. It moved towards products that, while incredibly durable when sealed, are ultimately disposable rather than endlessly serviceable, at least in theory. It really redefined product life cycles within that segment of the industry, and it changed consumer expectations for certain types of watches. And it's fascinating how we still see that kind of do. dole approach today. You have these cutting-edge synthetics for mass-produced sealed units,

but traditional shellac is still being used for delicate repairs and in high-end artisan craft where serviceability is paramount. There's still a balance. Precisely. It reflects the diversity of the watch world itself. So, okay, we've gone from tar and cheese through shellac, GS-hypo, super glue. And now this era of disposability, or at least non-serviceability, for some watches. Let's dive into the actual chemical arsenal a modern watchmaker has. It's not a just one kind of glue anymore, is it? It sounds like a whole palette of polymers, each tailored for specific jobs. That's a great way to put it a palette. The industry uses a really diverse array of adhesive chemistries, each picked for its unique properties and suitability. It's like

a specialized toolbox. Okay, so what are the main players in this toolbox? Well, first up, you have epoxy. These are workhorses, widely used for their high strength, their durability, and excellent resistance to chemicals and temperature. They're typically two-part systems you mix them, And a chemical reaction creates incredibly strong bonds. Where would you use those in a watch? Crucial for structural bonding. Think attaching glass or sapphire crystals to metal cases, bonding metal-to-metal components. Sometimes even for setting jewels, though that's often UV now,

you'll see things like quick-setting five-minute epochs for general repair, maybe specific jewelers epochs like Vigors, or even industrial-grade ones like Huntsman's Aeroldite, 2014-2 for really demanding applications. It's like aerospace grade stuff almost. Pretty much. Imagine that level of structural integrity scaled down to a tiny component in your watch. That's the kind of bonding we're talking about. Then there are silicones.

These are valued for completely different reasons. Exceptional flexibility, for one. They also handle a huge temperature range from cryogenic right up to high heat and offer superior moisture resistance. Flexible and resistant. Sounds good for sealing. Exactly. They come in various curing formats,

RTV room temperature vulcanizing is common, means they cure without needing heat, which is vital around delicate movements. Their main job in watchmaking is case sealing, creating those essential, airtight, and waterproof barriers. Dow's dowsilah adhesives are a prime example known for clarity and resilience. They're the invisible shields protecting the watch's heart. Silicones are also vital in smart watches for protecting sensitive electronics, sometimes even used for damping vibrations. Right, protecting delicate components, not just hold not just holding them. Precisely. Next up, polyurethanes. These are known for their toughness, their impact resistance, and strong adhesion to lots of different materials. They can be moisture

curing or two-part systems. In watches, they're used for structural parts and are particularly good as waterproof glues for case sealing. They provide really lasting results against water exposure. You might see chemistry is similar to what's used in automotive, like DuPont's beta seal, adapted for luxury goods where that robust impact resistance, is needed. Interesting. And what about the quick stuff? Super glue.

Yep. Sinoacrylates are instant adhesives. Still very much used. They cure extremely fast, right? Room temperature, strong bonds and seconds. Perfect for small, precise bonding where you need that immediate tack. And for high-end goods, they've developed specialized low blooming and low odor versions. Avoids that white residue, the blooming, you sometimes see, keeps things looking clean.

Ah, good point. In the last big category. UV curable adhesives. These are a really significant advancement because they offer amazing control. They polymerize or cure rapidly seconds to minutes, but only when exposed to specific wavelengths of UV light. Cure on demand. Exactly. Cure on demand allows for really precise positioning of components before you lock them in place.

They often have excellent optical clarity, which is key, primarily used for bonding watch crystals and glasses to bezzles and cases. Also very important for potting or sealing sense. sensitive electronic parts in smart watches, where that clarity and precise placement are critical. So it's way more than just the core glues. It's not like there's some highly specialized solutions, too, for very specific functions within the watch. Absolutely. Beyond those main chemistries, watchmaking relies on other things. Like thread lockers. Think lock tight. These are used to secure tiny screws and bolts against vibrations, snopping them from loosening over time. Importantly, many fornulations still allow for normal disassembly later. So they lock, but not permanently. Often, yes, depends on the grade you choose.

Then there are dial adhesives and tapes. These can be tiny self-adhesive dots or double-sided tapes. They're used for securing watch dials to the movement, especially useful if the original dial feet those little pins that hold the dial get broken during a repair. It's a common fix. Ah, practical solution. And then there's something really advanced. Surface Modification Codings.

Acculon is a name you might hear. Now, crucially, these are not adhesives than. themselves. Their nanoscale treatments applied to the surface first. To make the glue stick better? Essentially, yes. They work by directly functionalizing the substrate, chemically altering the surface at a nanoscale so the adhesive can form a much stronger, more reliable bond. It reduces the chance of delamination or failure. Plus, they can add other properties like making the surface repel water or fingerprints. It's about optimizing the surface for the adhesive.

That's fascinating. Really prepping the battlefield for the glue. A good analogy. It ensures the best possible performance. Okay. With all these advanced chemistries involves, who's actually making these super glues? And how do they even get into the hands of a watchmaker? Are giants like Dow, DuPont, Henkel, and Huntsman just, I don't know, shipping barrels of this stuff directly to Sonsora? Well, not directly, usually.

It's more indirect. These major global chemical manufacturers play a crucial role, but often behind the scenes. They're huge R&D efforts for really demanding industries, electronics, aerospace, automotive, produce materials that are directly transferable to horology. The requirements are often similar, precision, durability, resistance. So the watch industry benefits from R&D done for other fields? Absolutely. For instance, Dowell is instant adhesive, noted for small items like watches, great clarity, works in extreme environments.

DuPont has innovations in structural adhesives like urethanes and epoxy use in automotive, maybe EV battery sealing chemistries directly applicable to strong watch cases. Plus electronic materials like silicone lid seals. Henkel, they're the world's biggest adhesive provider. Their locktight brand is everywhere in watch repair and manufacturing. Thread lockers, retaining compounds, instant glues, UV curables, you name it. Locktite, yeah, I know that name. And Huntsman with their Aeroldite brand.

That's high performance epoxy, acrylics, polyurethanes. Again, often developed for demanding electronics or aerospace, needing that precise bonding and extreme durability perfect for advanced watchmaking. The watch industry is effectively leveraging solutions developed for other high-precision, high-reliability fields. It's a huge advantage. Okay, so the big guys make the base chemicals. How do they actually get to the watchmaker's bench? Right.

It's a sort of multifaceted supply chain. On one side, you have large industrial distributors. Bodo Muller, to me, is a good example. They're premier global distributors of specialty chemicals. They don't just ship boxes. They offer technical consulting. They have labs for testing applications. they provide training.

They might be an authorized Henkel distributor, for example. They bridge that gap between the massive chemical producers and the more bespoke needs of watchmaking. So they add expertise. Exactly. Then on the other side, you have the niche watch parts suppliers, companies like Perrin Watch Parts, Time Connection Inc, Eslinger & Co, Grobit USA. These catered directly to individual watchmakers and repair professionals.

They stock everything from the classic GS-Hipartes, type of cement and various lock-type products right back to traditional pure shalak sticks. Ah, so they serve the repair side and smaller makers more direction. Precisely. It's this dual supply chain that ensures the industry gets both the cutting-edge industrial solutions needed for mass production and the continuity of traditional materials essential for the artisanal side, for repairs, for heritage skills. It's a blended approach then. Giving watchmakers the best of both worlds, from, like you said, space-grade epochsies, right down to time-honored shalac.

That captures it perfectly. It sounds like adhesives are truly magical for watchmaking then. Enabling all sorts of innovations, unlocking new designs, cleaner looks, thinner cases. But there's always a flip side, isn't there? What are the inherent advantages clearly laid out? And what are the tradeoffs? Because I imagine, as powerful as these glues are, they must come with some real challenges, too. Oh, absolutely.

The upside, the advantages are compelling. You hit on some already. Huge design flexibility and aesthetics. Cleaner, sleeker looks without visible fasteners. Thinner, lighter watches become possible. They're fantastic at bonding to similar materials, metals, plastics, glass, composites. They overcome tricky issues like differing thermal expansion rates. Meaning things expanding or shrinking differently with heat?

Exactly. That difference can easily crack a less flexible bond or stress a mechanical joint. Adhesives can often accommodate that better. Allows for really innovative multi-material constructions. They also provide even stress distribution. A glued joint spreads the load over a larger area, unlike a screw which concentrates stress at one point. This improves strength, reliability, fatigue resistance. Makes sense. Fewer weak points.

Right. They also contribute to light weighting and cost reduction. Replacing heavier metal fasteners, streamlining manufacturing, reducing park counts, labor, potentially production costs. And critically, they create hermetic seals for environmental protection. vital for water resistance, keeping out moisture, dust, dirt. And finally, some flexible adhesives offer excellent vibration damping. They absorb shock, protecting delicate movements or sensitive electronics inside. Okay, that's a strong list of benefits. It also sounds too good to be true.

So what's the biggest headache? What are the real complexities and challenges for a watchmaker or manufacturer working with these high-tech glues? The challenges are significant and shouldn't be underestimated. First off, surface preparation and quality control. This is absolutely critical. Any tiny bit of impurity, oxidation, grease, or contaminant on the surface can lead to weak bonds or outright failure. You can get defects like kissing bonds where surfaces touch but don't truly bond chemically or porosity.

Voids? Tiny air bubbles trapped in the glue line. And these are hard to spot. Incredibly hard, especially in miniaturized components. It demands meticulous cleaning protocols and rigorous quality checks. Get the prep wrong, the bond will fail. eventually. Then there are the curing processes and potential defects. If the adhesive isn't mixed correctly, if it's past its pot life, if the temperature or humidity isn't right during cure,

all these things can drastically reduce the final bond strength. And again, these defects might not show up immediately, but lead to premature failure down the line. So consistency is key. Paramount. Long-term durability under environmental stress is another huge factor. Watch bonds face a tough life. Extreme temperatures, constant heating and cooling cycles, UV radiation from sunlight, moisture, chemicals from sweat or the environment, all can degrade the adhesive over time. It can become brittle, lose adhesion, dilaminate, and there's also long-term creep to consider where a bond under constant stress slowly deforms permanently. Right. It's not just about initial strength, but strength over years. Exactly. Miniaturization

and precision application also pose hurdles, applying tiny precise amounts of adhesive without getting it where it shouldn't be, without damaging delicate parts. It's true. challenging. There's also the risk, especially in smartwatches, of outgassing volatile compounds released from the adhesive during or after cure potentially contaminating sensitive electronics. Chemical compatibility is vital. And the big one we touched on earlier. Yes. Disassembly and recyclability. This is a major challenge, starkly highlighted by that swatch example. Many high-performance structural adhesives are designed to be permanent. That's their strength, literally. But it makes components impossible to service, as the source said, or incredible.

difficult to take a part for repair or recycling without causing damage. So durability clashes with sustainability. There's a definite tension there, a tension between achieving the ultimate product durability and robustness through permanent bonds and the growing imperative for repairability, for sustainability, for a more circular economy. It's a tough balance for the industry. So to wrap up, adhesives have clearly evolved way beyond just simple glues. They're fundamental enablers of modern watch design, performance, manufacturing efficiency. They're constantly pushing the boundaries and precision and aesthetics.

They really are the unsung heroes of modern watchmaking. That's the essence of it, absolutely. And the science isn't standing still. The continued evolution of adhesive chemistry promises even further advancements, offering potential solutions to current challenges, especially that tricky tension between making things last forever, sealed tight, and making them repairable or recyclable. It's a fascinating tightrope walk for the industry going forward. Which leaves us with a final thought for you, the listener. If modern watchmaking increasingly relies on these maintenance-free designs,

often enabled by permanent adhesives, what does this shipped from a tradition of the repairable heirloom to potentially more disposable technology mean for our understanding of craftsmanship, value, and consumer expectations in the future?