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Matt Seal S-250: A Technical Overview
Matt Seal S-250 is a neutral-cure, high-flexibility silicone formulated for general purpose and sanitary sealing. With anti-fungal protection, UV stability, and a ±30% joint movement rating, it’s ideal for interior and exterior joints exposed to moisture, movement, or sunlight. The matt finish gives a professional look on visible joints, while the product adheres exceptionally to substrates including Colourbond, ceramic tiles, aluminium, glass, and timber — often without priming. With low VOC content and high durability, it’s suitable for hygienic environments and harsh Australian climates.
±30%
Joint Movement Capability
Core Features & Specifications
- Neutral oxime cure, non-corrosive to metals and concrete
- VOC 43 g/L – suitable for Green Star environments
- Cures with atmospheric humidity – ideal for open applications
- Elastic recovery >90% for crack-resistance under thermal stress
- Excellent adhesion to zincalume, aluminium, glass, PVC and more
- Temperature resistance from -50°C to +150°C
- Available in a wide range of colours, including Arctic White, Ebony and Misty Grey
The Matt Seal S-250 Advantage
- Protects against mould in high-humidity environments like showers, spas and kitchens
- Prevents call-backs with long-lasting adhesion even in dynamic joints
- Allows fast application — skin time of ~10 minutes enables quicker tooling
- Minimises inventory — one sealant for internal, external, kitchen, bath and façade use
- Ideal for Australian conditions with permanent UV resistance and low odour
Best Practices: Do's & Don'ts
Do
- Use a two-wipe method and white spirit for non-porous surface prep
- Mask edges to achieve a clean joint line and remove tape while sealant is still wet
- Use backing rod for joints deeper than 10mm and maintain 2:1 width:depth ratio
Don't
- Apply in totally enclosed spaces – silicone needs humidity to cure
- Use on mirrors, aquariums, polycarbonate, or trafficable surfaces
- Paint over the cured sealant – it's not paintable
Applications in Practice: Trade Scenarios
For Plumbers (On-site Installer): Shower Recess Sealing
The Engineering Challenge
Sealing between tiled walls and shower trays often fails due to constant moisture and movement from thermal expansion. A sealant must resist mildew and adhere to glazed ceramics under daily wet conditions.
The System-Based Solution with Matt Seal S-250
Apply a 10x10mm bead of Matt Seal S-250 post-tiling. Use masking tape to define the joint edge, gun at a 45º angle, and tool off within 5 minutes. The anti-fungal system and elastic recovery ensure longevity in steam and wet zones.
Best Practice Note
Ensure substrate is dry and cleaned with white spirit. Use Primer 2001 on porous surfaces if needed.
For Builders (Business Owner): External Cladding Movement Joints
The Engineering Challenge
Exterior panels and cladding expand under solar exposure. Inadequate sealants fail due to UV, shrinkage or poor adhesion to coated metals like Colourbond and zincalume.
The System-Based Solution with Matt Seal S-250
Matt Seal S-250 maintains elasticity and UV resistance, bonding directly to coated metal. For 20x10mm joints, apply a backing rod and gun sealant in a single pass, tooling to concave finish.
Best Practice Note
Avoid 3-sided adhesion. Use polyethylene tape to allow 2-sided bonding and joint movement.
Performance Benchmark: Matt Seal S-250 vs. Standard Alternatives
| Metric | Matt Seal S-250 | Standard Alternative | Advantage |
|---|---|---|---|
| Movement Capability | ±30% High Flex | ±15% | Double the flexibility — prevents cracking in wider joints |
| VOC Content | 43 g/L Low Emission | 130–150 g/L | Safer indoor use and meets Green Star criteria |
| UV Resistance | Excellent Long-Term Outdoor Use | Moderate | No degradation or chalking under full sun |
Frequently Asked Questions
Can Matt Seal S-250 be used in showers or bathrooms?
Yes, Matt Seal S-250 is specifically formulated for sanitary applications including showers, wet walls, and floors. It contains an anti-fungal additive that resists mould and mildew even in high humidity environments.
What substrates does Matt Seal S-250 adhere to?
Matt Seal S-250 adheres strongly to ceramic tiles, glass, aluminium, PVC, zincalume, colourbond, treated timber, and more. Always test for adhesion and use recommended primers for porous surfaces.
Is Matt Seal S-250 paintable?
No, Matt Seal S-250 is not paintable. It is designed for visible finish applications and comes in a variety of colours to suit project aesthetics without the need for overcoating.
What is the skin time and curing speed?
Matt Seal S-250 develops a skin in approximately 10 minutes at 25°C and 50% RH. It cures at a rate of around 2mm per day, depending on temperature and humidity conditions.
Can I use Matt Seal S-250 in kitchens and food prep areas?
Yes, this sealant is safe for use in food preparation zones once cured, thanks to its neutral cure, low VOC formulation and compliance with hygienic sealing requirements.
Applications & Benefits
| Application / Use Case | Key Benefit | Primary Trades |
|---|---|---|
| Shower wall and floor joints | Anti-fungal and waterproof – prevents mould growth in wet zones | Plumbers, Tilers |
| Kitchen and laundry sealing | Low VOC and food-safe when cured – suitable for hygienic environments | Cabinetmakers, Builders |
| Metal façade and cladding joints | High UV stability and joint movement capability – handles seasonal expansion | Builders, Façade Contractors |
| HVAC and ductwork sealing | Flexible and weather-resistant – maintains bond under thermal cycling | Mechanical Contractors |
| Boat and marine applications | Waterproof and tough – durable under high moisture exposure | Boatbuilders, Marine Technicians |
Applying Matt Seal S-250 Silicone Sealant: Enhanced Protocols & Best Practices
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Surface Preparation
All surfaces must be stable, dry, and free from dust, oils, or release agents. Use a two-wipe method with clean, lint-free cloths and white spirits for non-porous substrates.
Method A: Non-Porous Surfaces
Clean with white spirits using two-wipe technique. Change cloths regularly to avoid recontamination.
Method B: Porous Substrates
Ensure substrate is dry and dust-free. Apply Primer 2001 using a small brush and allow to dry fully.
Timing: Ensure concrete is cured at least 28 days prior to sealant application.Pro Tip: Mask joint edges before applying sealant for a neat, professional finish. -
Joint Design & Priming
Ensure joints have a 2:1 width-to-depth ratio. Use a closed-cell polyethylene backing rod in joints deeper than 10mm.
External Joints
Minimum width: 10mm. Max width: 30mm. Insert backer rod to limit depth to 10–15mm.
Internal Joints
Minimum joint width: 5mm. Ensure sealant contacts only two sides of joint.
Timing: Allow primer to dry for several minutes before sealant application.Pro Tip: Use release tape on the third surface to prevent three-point adhesion failures. -
Sealant Application
Apply between 5°C and 40°C. Cut nozzle at 45° and use a caulking gun to apply a smooth, continuous bead ensuring full joint contact.
Manual Application
Use steady forward pressure to avoid air pockets. Push bead into joint while moving the gun forward.
Tooling
Tool the joint with a moistened spatula within 5 minutes of application. Remove masking tape immediately afterward.
Timing: Skin forms in ~10 minutes; allow 2mm/day cure rate at 25°C and 50% RH.Pro Tip: Keep white spirits nearby for immediate clean-up while silicone is still uncured. -
Curing & Post-Cleaning
Avoid disturbing the joint during the initial cure. For dried silicone, use white spirits to soften, then remove with a scraper.
Uncured Removal
Wipe excess silicone with white spirits and a clean cloth immediately after application.
Cured Removal
Soften using white spirits, then carefully remove with a plastic scraper or razor blade.
Timing: Full cure achieved at ~2mm depth per 24 hours depending on ambient conditions.Pro Tip: Do not expose to water or cleaning agents until fully cured for at least 24–48 hours.
Limitations & Safety
Product Limitations
Not suitable for structural glazing. Use Adheseal N-80 or N-60
Do not use in fully enclosed areas without humidity – the sealant requires atmospheric moisture to cure.
Not recommended for underwater use (e.g., swimming pools).
May stain or discolour natural stone, copper, and brass – always perform pre-testing. Test before use
Not paintable – select colour at time of purchase to match aesthetic needs.
Safety & Handling Requirements
Personal Protective Equipment
Wear gloves and safety glasses when applying or tooling the product. Avoid direct skin contact during use.
Ventilation Requirements
Use in well-ventilated areas. If used indoors, provide adequate airflow to ensure safe curing and to limit vapour build-up.
Fire & Handling Precautions
Store between 10°C and 35°C in a cool, dry place. Avoid exposure to open flames or ignition sources during application and curing.
Emergency First Aid
Eyes:
Flush gently with lukewarm water for 5 minutes. Seek medical advice if irritation persists.
Skin:
Remove contaminated clothing. Wash affected area with lukewarm water. If irritation occurs, seek medical attention.
Inhaled:
Move to fresh air. If breathing difficulty continues, contact a medical professional immediately.
Swallowed:
Rinse mouth and drink water. Do not induce vomiting. Seek medical attention or contact Poisons Information Centre (AU: 13 11 26).
Seek medical attention immediately in all cases of serious exposure.
Matt Seal S-250 Silicone Sealant Application Guide
Ceramic & Porcelain Tiles
Surface Preparation
Ensure tile surfaces are clean, dry, and free from soap scum, grease, or dust. Wipe with white spirits and use the two-wipe method for best adhesion.
Primer Requirements
No primer typically required
Direct adhesion is excellent on glazed and unglazed ceramics.
Aluminium & Metal Cladding
Surface Preparation
Remove all surface oxidation and oil films with a suitable solvent. Use a clean, lint-free cloth and change frequently during prep.
Primer Requirements
Primer recommended for optimal adhesion
Apply Primer 50A for non-porous substrates if exposed to heavy movement or weathering.
Primer 50ATimber (Treated or Painted)
Surface Preparation
Ensure timber is clean, dry, and fully cured. Remove any loose paint or coatings. Sand lightly if surface is glossy.
Primer Requirements
Primer recommended for optimal adhesion
Use Primer 2001 for porous wood surfaces or where moisture exposure is high.
Primer 2001Glass & Glazing Applications
Surface Preparation
Clean glass with isopropyl alcohol or white spirits. Ensure all residues and films are removed to avoid adhesion failure.
Primer Requirements
No primer typically required
Excellent direct adhesion to glass for sanitary and façade sealing.
PVC & Plastics
Surface Preparation
Wipe with white spirits to remove oils and release agents. Check for compatibility and test adhesion on unfamiliar plastics.
Primer Requirements
Primer recommended for optimal adhesion
Use Primer 50A when dealing with smooth or high-gloss PVC surfaces.
Primer 50A
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