Silicone sealant is a form of bonding agent, used to create water and airtight seals at the joint between two surfaces. When first applied, the sealant has a gel-like consistency, and then once cured, it dries to a more flexible, rubber material. Silicone sealants are often preferred over other sealants due to their high degree of elasticity and durability. Once fully cured, they provide a hardwearing flexible bond that can withstand fluctuating temperatures and high levels of humidity.

Drying Time of Silicone Sealant

It is important to determine the difference between drying and curing when it comes to silicone sealants.

Drying is the initial phase directly after application, where the ambient humidity comes into contact with the sealant, leaving it dry to touch. It usually takes around 30 minutes to an hour for the sealant to dry.

Curing however, takes a significant period of time, and it is essential that the sealant is undisrupted during this time to enable the waterproof seal to form. Once exposed to oxygen the curing process begins typically taking between 24-48 hours. When applying the sealant, it is fundamental that you check the manufacturers guidelines for your specific sealant.

Factors Affecting Sealant Drying 

The drying time of silicone sealant is influenced by several factors:

• Temperature

The warmer the temperature, the faster your sealant will cure. This is partially down to the fact that warmer temperatures tend to involve a higher humidity. The ideal temperature range for sealant cure rate is between 15-25℃. You should not apply any sources of direct heat to the sealant as this may have an adverse effect, softening and melting the silicone.

• Humidity

Humidity speeds up the curing time, the increased moisture in the air decreases the time taken for the silicone sealant to fully cure. It may be advisable to use a humidifier in the areas where the sealant has been applied to accelerate cure time.

• Thickness of Sealant

The larger the volume of sealant used in one area, the slower the cure rate of the silicone. This is because most formulas cure from the outside inwards, and so the greater the amount of product used, the longer this will take.

• Type of Silicone Sealant Used

Specialised formulas of silicone sealants may have a different chemical structure, that requires a longer curing time. These sealants may be able to withstand higher temperatures, or retain a higher degree of elasticity once applied.

Quick Tips for Accelerating Drying

To achieve faster drying times with your silicone sealant, there are a few steps you can take:

• Proper surface preparation 

Make sure the application surfaces are clean and dry, free from any contaminants.

• Create ideal environmental conditions for the sealant to cure efficiently  

Placing a humidifier in the room where the sealant has been applied can speed up the drying and curing rate. This rate can be further increased by ensuring that the temperature of the application area remains between 15-25℃. 

Common Mistakes to Avoid

Here are some common errors to avoid which may affect your sealant drying time:

• Overapplication of sealant
• Not taking into consideration the environmental conditions
• Selecting the wrong type of sealant

Testing Dryness of Silicone Sealant

Testing if the silicone sealant has dried is essential. It is important that you wait the recommended time for drying as disruption of the sealant prior to drying and curing may affect the durability and life span of the seal. To test if the sealant is dry you should observe any changes in colour and gently touch the surface to determine if the product is tacky or not.

FAQs about Sealant Drying

What does the term ‘skinning over’ mean?

This means that the product has begun to cure and has developed a firm skin on its surface

Why is my sealant not fully curing?

Prior to application, it is important to check your product’s expiry date as a silicone sealant beyond its shelf life should not be used, as it may not fully cure.