When a sealing application is exposed to sunlight, rain, humidity, temperature changes and continuous movement, choosing the right silicone sealant becomes critical. A standard sealant may not provide the combination of flexibility, weather resistance and long-term adhesion required for demanding outdoor applications.
This is where 789 silicone, also referred to as silicone 789, can be an effective solution for weatherproof sealing and bonding applications.
Fasto Redisil 789 Pro is a one-part, weather-grade, neutral-cure RTV silicone sealant developed for long-term outdoor performance. It is designed to maintain an elastic seal under environmental exposure while providing strong adhesion to a variety of substrates.
What Is 789 Silicone?
789 silicone is a weather-grade RTV silicone sealant designed for applications where long-term environmental resistance and flexible sealing are important.
The Fasto Redisil 789 Pro formulation uses a neutral-cure system, making it suitable for applications involving metals, glass and other sensitive substrates where a non-corrosive curing system is preferred.
Unlike rigid joining materials, silicone sealants remain flexible after curing. This flexibility allows the cured seal to accommodate movement caused by thermal expansion, vibration and changes in environmental conditions.
Fasto Redisil 789 Pro is supplied as a one-part sealant, making it convenient for cartridge or sausage-gun application without requiring on-site mixing. It is available in 280 ml cartridges and 600 ml sausages.
Why Choose Silicone 789 for Outdoor Applications?
Outdoor sealing applications are exposed to conditions that can gradually degrade an unsuitable sealant.
Common challenges include:
- UV radiation
- Rain and moisture
- High humidity
- Temperature fluctuations
- Thermal expansion and contraction
- Vibration and movement
- Air and water infiltration
A weather-grade silicone needs to maintain its flexibility and adhesion while exposed to these conditions.
Fasto Redisil 789 Pro is designed with UV and weather resistance, high flexibility and a wide service temperature range of -24°C to 180°C.
This makes silicone 789 suitable for applications where maintaining a durable elastic seal is more important than creating a rigid joint.
Neutral Cure Silicone: Why Does It Matter?
One of the important characteristics of 789 silicone is its neutral-cure technology.
Neutral-cure silicone sealants are designed to cure without producing the acidic by-products associated with acetoxy-cure systems. This can be particularly useful when sealing or bonding substrates that may be sensitive to corrosive curing by-products.
Fasto Redisil 789 Pro is described as a neutral-cure and non-corrosive RTV silicone sealant, making it suitable for metals, glass and sensitive construction substrates.
This characteristic can be especially valuable in:
- Aluminium structures
- Glass assemblies
- Metal joints
- Facade systems
- Curtain wall systems
- Outdoor construction
- Industrial assemblies
Key Benefits of 789 Silicone
1. Excellent UV and Weather Resistance
Outdoor sealants must withstand continuous exposure to sunlight and changing weather conditions.
Fasto Redisil 789 Pro is engineered for outdoor applications and provides UV and weather resistance for demanding environmental conditions.
2. High Flexibility
Building materials and industrial components can move because of thermal expansion, vibration and structural movement.
A flexible silicone seal can accommodate this movement while maintaining the seal.
Redisil 789 Pro is designed for expansion, control and structural joints where movement capability is important.
3. Strong Adhesion to Multiple Substrates
A sealing application may involve more than one material.
Fasto Redisil 789 Pro can adhere to substrates including:
- Glass
- Aluminium
- Steel
- Concrete
- Stone
- Plastics
- Rubber
This broad substrate compatibility makes it suitable for multi-material sealing and bonding applications.
4. Wide Temperature Resistance
Temperature changes can place significant stress on sealed joints.
789 silicone provides a service temperature range of -24°C to 180°C, helping it perform across a broad range of operating environments.
5. Protection Against Water and Air Ingress
Properly designed and applied silicone joints can help prevent unwanted water and air penetration.
This is particularly important for facade, glazing, curtain wall and exterior construction applications where moisture ingress can affect long-term assembly performance.
Applications of Silicone 789
Properly designed and applied silicone joints can help prevent unwanted water and air penetration.
This is particularly important for facade, glazing, curtain wall and exterior construction applications where moisture ingress can affect long-term assembly performance.
Structural Glazing and Facade Sealing
Glass and aluminium facade systems require durable seals that can accommodate movement while maintaining weather protection.
789 silicone can be used for glass-to-aluminium structures and facade interfaces where flexibility, weather resistance and adhesion are required.
Curtain Wall and Mullion Joints
Curtain wall systems are continuously exposed to outdoor environmental conditions.
Silicone 789 can be used for mullion and curtain wall joints where long-term joint integrity and movement capability are important
Expansion and Control Joints
Expansion and control joints are designed to accommodate movement within a structure.
A flexible RTV silicone can help maintain joint sealing performance as substrates move due to thermal or structural changes.
Glass and Composite Bonding
Glass panels and composite structures often require a sealant capable of maintaining adhesion while accommodating movement.
Redisil 789 Pro is designed for glass and composite bonding applications requiring weather-grade durability.
Tile, Granite and Stone Sealing
Silicone 789 can also be used for joint sealing involving tile, granite and stone where flexibility and crack-bridging capability are required.
Outdoor Construction Sealing
Exterior construction joints can experience continuous exposure to humidity, rain, temperature variations and UV radiation.
A weather-grade neutral-cure silicone provides an elastic barrier designed for these conditions.
How to Apply 789 Silicone Correctly
Even a high-performance sealant requires proper surface preparation and application.
Step 1: Prepare the Surface
Remove:
- Dust
- Dirt
- Oil
- Grease
- Rust
- Loose coatings
- Frost
- Other contaminants
The substrate should be clean and suitable for bonding.
Step 2: Clean the Substrate
Use an appropriate cleaner to remove remaining contamination before application.
For critical applications, substrate compatibility and adhesion should be evaluated before full-scale production.
Step 3: Prepare the Joint
Where required, install appropriate back-up material, joint fillers, setting blocks, spacers and masking tape.
Proper joint design is important for achieving the intended sealing performance.
Step 4: Apply Silicone 789
Apply Redisil 789 Pro using a manual or pneumatic dispensing gun.
Extrude a continuous and uniform bead into the joint.
Step 5: Tool the Sealant
Tool the sealant before skin formation to achieve proper contact with the substrate and a clean finished joint.
Remove masking tape after tooling and before the sealant skins over.
Fasto specifies a skin formation time of approximately 15–25 minutes, tack-free time of 40–60 minutes, and full cure of approximately 7–14 days, depending on humidity, temperature and joint depth.
789 Silicone vs Standard Silicone Sealant
Not every silicone sealant is designed for the same application.
When selecting a silicone sealant, manufacturers and contractors should consider:
Requirement | What to Look For |
Outdoor exposure | UV and weather resistance |
Metal substrates | Neutral-cure, non-corrosive system |
Thermal movement | High flexibility and movement capability |
Multiple substrates | Broad substrate adhesion |
Temperature variation | Appropriate service temperature range |
Façade and glazing | Weather-grade sealing performance |
Application efficiency | One-part, ready-to-use formulation |
The correct sealant should always be selected according to the substrate, joint design, environmental exposure and required performance.
Where Can Silicone 789 Be Used?
Silicone 789 is particularly relevant to applications such as:
- Structural glazing
- Facade sealing
- Curtain wall systems
- Aluminium and glass assemblies
- Expansion joints
- Control joints
- Outdoor construction
- Stone and granite joints
- Composite structures
- Multi-substrate industrial sealing
For manufacturers, contractors and fabricators, selecting a sealant based on the actual operating environment can help improve joint durability and reduce premature sealing failures.
Why Fasto Redisil 789 Pro?
Fasto Redisil 789 Pro combines the characteristics required for demanding weather-grade sealing applications in a ready-to-use one-part RTV silicone formulation.
Its key characteristics include:
- Neutral cure
- Non-corrosive curing system
- UV and weather resistance
- High flexibility
- Movement capability
- -24°C to 180°C service temperature
- Adhesion to glass, aluminium, steel, concrete, stone, plastics and rubber
- Black, grey and white colour options
- 280 ml cartridge and 600 ml sausage packaging
For businesses looking for 789 silicone, silicone 789, or a weather-grade neutral-cure RTV sealant, Redisil 789 Pro is designed for applications where long-term outdoor sealing performance is essential.
