How do you use the right sealant for the job? Here, Andy Cummins, senior product manager at Geocel delves into the science behind high-quality silicone sealants, so you can be sure you’re delivering a long-lasting and reliable finish.

Sealants form a key part of any tradesperson’s tool kit, including glazing fitters and fabricators, with a variety of uses and applications. While the ability to achieve both a high-quality finish and a seal that is neat and durable is largely dependent on the skill of the applier, the quality of the sealant itself also has a very real part to play.

Choosing the right sealant for the job is essential, especially when it comes to exteriors and windows, needing to tick all the boxes for flexibility, weather resistance and excellent adhesion. Sealants may look the same on the surface of the cartridge but the science and ingredients behind their formulations can differ across the shelf.

If the product is poor, you face a higher chance of call backs and having to revisit an old job to make it right – bad for both your wallet and your reputation.

Here, knowledge truly is power. Once you understand what makes a high-quality sealant so great, you’ll be able to separate the best from the rest.

Even when applied correctly and in ideal conditions, cheap sealants are less likely to perform as expected. This is because they can be bulked out with other chemicals and additives that evaporate as they cure, causing the sealant to shrink and not form a strong bond.

What may initially seem like an easy cost-based decision, can actually end up costing you more in the long-term.

Lower quality sealants are also less likely to withstand challenging conditions in the long term. For exterior applications, one of the biggest risks to an effective installation is the weather. Ultraviolet (UV) radiation, rain, wind and significant changes in temperature can all impact the lifespan and efficacy of a sealant.

As such, the product selected needs to have a high level of durability, UV and weather resistance to be able to withstand these conditions, season after season.

Another consideration when it comes to glazing is that there will always be a significant amount of movement expected between the frame and the rest of the building. Changes in temperature will also cause the frame to expand and contract over time, meaning sealants must maintain a degree of permanent flexibility to ensure they can accommodate movement long-term.

Here a high-quality silicone sealant will deliver a flexible seal, adhere to the wide range of common substrates and offer excellent resistance to the effects of weather and changes in temperature. Good quality silicone sealants will not crack, shrink or discolour for a longer-lasting finish that retains its appearance and performs well.

Watch out for…

The vinegar smell when curing: That sharp smell isn’t just unpleasant, it signals acetoxy-cure chemistry, which releases acetic acid as it sets. This can present a challenge with adhesion, especially when working across a variety of substrates. For glazing jobs, a neutral-cure product is always the safer choice, bonding better to porous surfaces.

A silicone blend without specifics: This can mean that the silicone polymer has been partially substituted with cheaper organic materials. It’s these additives that break down under UV and temperature cycling.

No elongation figure: This tells you how far the sealant can stretch before it tears. For a joint that moves with temperature expansion, you will want a high number – anything from 400% upwards. Budget sealants typically skip this figure entirely.

No gimmicks, just science
At Geocel, the focus is firmly on the science. With a dedicated research and development team, we have set the standard in performance, reliability and quality. All our products under the newly consolidated ‘Powered by Dow’ range benefit from premium grade silicone from Dow, the global leader in silicone technology, with all additional ingredients carefully selected to enhance performance for its specific application.

Take Frame Silicone for example. Specifically designed for glazing applications, this sealant has a neutral-cure and a 700% elongation figure. It offers good joint movement capabilities and, once cured, will remain flexible and totally water resistant throughout its long service life.