Description
Crommelin Blackseal Heavy Duty is a black, water-based bitumen waterproofing membrane for below-ground and other non-UV-exposed surfaces, supplied here in a 15L pail for larger jobs. It is a bitumen emulsion modified with a synthetic rubber co-polymer. It dries to a strong, flexible film that stays watertight in permanently wet conditions, which makes it a practical, economical choice where the finished membrane will stay out of sight and out of the sun.
About the formula
A water-based bitumen emulsion with a synthetic rubber co-polymer for added flexibility and strength. It grips well to a wide range of building surfaces and is designed to help prevent the damage that moisture transfer causes, including efflorescence, mould growth, staining and paint peeling. The manufacturer describes it as non-toxic, non-flammable, fast drying and suitable for permanent immersion. It can be thinned with up to 50% water if you want a bitumen paint instead of a full-strength membrane.
Where to use it
Indoors: not intended for interior wet areas such as showers or bathrooms, because it cannot be tiled over or finished with a top coat.
Outdoors: below-ground and non-exposed outdoor surfaces, including garden retaining walls, planter boxes, plant pots, timber posts and water tanks. It suits non-critical waterproofing jobs, not areas next to habitable spaces.
Suitable surfaces include concrete, concrete blocks, brickwork and other masonry, renders, cementitious substrates, compressed cement and fibre cement sheeting, natural stone, plywood sheeting and timber. It also works on aluminium and steel that have been suitably prepared.
How to use it
Start with a clean, sound surface free of dust, grease, loose material and flaking coatings. Stir the pail well, then apply with a brush or roller. Two coats are recommended, and the 15L pail covers about 11.25 square metres at that rate. Let each coat dry before applying the next. Mix with water only if you want to thin it for use as a bitumen paint, and do not go past 50% dilution. Wash tools with water straight after use, before the product dries. Check the current Crommelin product information sheet for recoat times and full preparation advice before you start.
Important notes
Do not paint, tile over or over-coat this membrane, and do not use it on trafficable surfaces. It is not suitable where UV stability is required, so keep it covered or buried. For shower areas or UV-exposed roofs and walls, choose a purpose-made Crommelin membrane instead. Because it is for non-critical applications only, it is not a substitute for a compliant waterproofing system in habitable or wet areas. Cure times vary with temperature, humidity and airflow, so allow enough time before backfilling or exposing the membrane to heavy moisture.
Specifications
| Brand |
Crommelin |
| Product |
Blackseal Heavy Duty Bitumen Waterproofing Membrane |
| Pack |
15L pail |
| Colour |
Black |
| Base |
Water-based bitumen emulsion modified with synthetic rubber co-polymer |
| Application |
Brush or roller |
| Number of coats |
2 |
| Coverage |
About 11.25 square metres per 15L (two coats) |
| Dilution |
Up to 50% water to make a bitumen paint |
| Clean up |
Water, while wet |
| Use |
Below ground and non-UV-exposed areas only |
Safety
Use it with good general ventilation. Normal site protection such as safety glasses and overalls is sensible, along with good hygiene. Store the pail sealed, away from extreme temperatures and freezing, and keep it away from strong oxidising agents, strong acids and strong bases. Do not let large spills reach drains or waterways. Refer to the Safety Data Sheet (SDS) for full details.
