Bonding Glass: The Basics
Glass is a unique substrate that can prove challenging to bond when it comes to both hot melt and non-hot melt adhesives. When working with glass, you’re not often working with load-bearing seams. Instead, you’re likely completing a project that must hold up to regular environmental changes with a bond that remains invisible and flawless all the while.
Therefore, the adhesive you use to bond glass to either itself or another substrate must be carefully thought out. You want it to be strong enough to create a water-tight bond, flexible enough not to snap under multi-directional pressures and clear enough to not be easily seen —even years into the future.
At Hotmelt.com, we’re here to help you learn from our years of trials with glass and all the different kinds of hot melt and non-hot melt adhesives you can use to secure it. Here are several different types of adhesives and application methods to help you with a flawless glass installation, whether it’s on the job, in the factory or for an at-home DIY project.
Non-Hot Melt Adhesives for Bonding Glass
An epoxy cure is the result of an exothermic reaction that cross-links polymers. Changing chemicals, temperature and other catalysts can transform the properties of this non-hot melt adhesive to fit nearly every application. This means an epoxy bond can be used on a variety of substrates, including glass.
Two-component, or two-part, epoxies are cured at lower temps than their one-component counterparts. These adhesives are superior in stability, temperature resistance and curing times. And better yet, two-part epoxies can be developed to be clear for use in highly-visible situations, such as glass installations.
The high stability combined with its ability to resist harsh chemicals and extreme heat makes epoxy an excellent solution in industrial settings, including aerospace and medical equipment.
Epoxies can be engineered to resist degradation caused by water, weather, ozone, oxygen, petroleum solvents, lubricating oils, jet fuels, gasoline, alcohol, salt solutions, mild acids and alkalis, and many other organic and inorganic compounds. Some of our favorites are apart of the Infinity Bond line.
This non-hot melt adhesive is a great candidate for glass substrates due to its strong, clear and waterproof bond. Super glue can be found in a variety of viscosities, so it can be adapted to fit any use — whether that’s setting in a matter of seconds on a production line or in a matter of minutes, so it can be manipulated during a delicate installation.
Super glue itself can create a bond that’s just as fragile as glass. A rubberized or plasticized version, such as our Rubber and Plastic Cyanoacrylate Super Glue, can make for a more flexible and lasting bond. However, it will still work best in tensile situations in which elements resist tension (being pulled apart) instead of compressive situations in which elements resist compression (being pushed together).
Overall, high-impact strength requirements should be avoided when using super glue on glass — making it great in highly visible and delicate applications that won’t be handled or bear weight on a regular basis.
Hot-Melt Adhesives for Bonding Glass
Silicone sealant is a liquid form of adhesive that often looks, feels and acts like a gel. It comes in a variety of types including high-temp, electric-grade and multi-purpose. Silicone can be applied using commercial-grade extrusion devices, heavy-duty or crafting glue guns, along with hand-held caulking tools.
Because glass doesn’t swell and shrink the way wood does, a flexible adhesive like silicone is a great fit in high-stress bonds, such as those in rigid glass applications. Silicone is a powerful adhesive, but its high flexibility and long curing time compared to many other hot melts make it a better fit for glass, car engines and other tight-but-flexible applications, instead of weight-bearing seals or those that need to be painted over.
Since it’s also weather resistant, waterproof and resists mildew growth, it’s very common to use silicone when bonding glass to itself, such as in aquariums or to wood or plastic like in window and bathroom installations. Silicone is truly a great adhesive for glass and a variety of other substrates — as long as you understand what kind of silicone you’re working with.
Acetoxy silicones release acetic acid and cure relatively quickly. Compared to most other silicones, they bond well with a variety of standard substrates. The acetic acid emissions can prove harmful to sensitive electronics and can prove corrosive in some applications, but some are also biocompatible and can be used in the manufacturing of medical devices.
Neutral curing silicones include oxime and alkoxy, which release methyl ethyl ketoxime and alcohol respectively as they cure. Unlike their acetoxy counterparts, this makes them non-corrosive and a great fit in electronic applications.
Hot Melt Glue Guns and Glue Sticks
Hot melt guns are used to apply hot melt glue sticks in situations where a small amount of adhesive needs to be applied precisely. These applicators focus on cut-offs and eliminating strings and trails, and they are often used in narrow spaces in in woodworking, packaging, bathroom and kitchen installations, and more.
But before you just start pointing and squeezing, there are a few measures to take to ensure a strong bond before turning your hot melt glue gun and glue sticks loose on a glass substrate:
- First, triple-check that the glass is clean so that the adhesive will stick to it instead of any oils or solvents on its surface.
- Next, rough up the areas to be bonded with an abrasive, like wet and dry paper to help the glue adhere stronger and longer.
- Finally, be sure you’re using a hot melt glue stick that’s specially formulated to work on a non-porous, hard surface like glass. We like Ad Tech 236 Universal High Temp Hot Melt for a superior bond, even on slick surfaces. We also love the Infinity Awesome Acrylic Hot Melt Glue Sticks for glass applications.
We know how tough it can be to find the best adhesive for bonding typical substrates — much less glass that calls for flexible, invisible, yet still strong properties in its adhesives. At Hotmelt.com, we have a wide variety of both hot melt and non-hot melt adhesives and applicators to choose from to suit your needs.
Questions? We Are Here to Help
If you still have questions about which solution is best for your glass bonding needs, contact us. One of our adhesive experts can help you find the perfect product and application method.