Description
Crommelin Blackseal Heavy Duty is a water-based, rubber-modified bitumen waterproofing membrane for below-ground and other non-UV-exposed surfaces, supplied here in a 1L size that suits planter boxes, pots, timber posts and small retaining wall jobs. It is made for surfaces that stay damp or wet and will not be painted, tiled or covered with a finishing coat.
About the formula
Crommelin describes Blackseal as a commercial grade bitumen emulsion modified with a synthetic rubber co-polymer. The rubber modification keeps the cured film flexible, so it stays watertight under permanently wet conditions and is suitable for permanent immersion. It helps prevent the damage that moisture transfer causes, including efflorescence, mould growth, staining and paint peeling. It grips a wide range of substrates, is fast drying, and the maker lists it as non-toxic and non-flammable. It can be thinned with up to 50% water to make a bitumen paint.
Where to use it
Indoors: not intended for interior finishing work or any area that needs a paintable or tileable surface.
Outdoors: below-ground and non-exposed exterior surfaces such as garden retaining walls, planter boxes, plant pots, timber posts, water tanks and other non-critical moisture barrier jobs.
Suitable materials include concrete, masonry, cement sheeting, timber and metal (check the label for the full substrate list and do a small test area first).
How to use it
Start with a clean, sound surface free of dust, grease, loose material and anything that could stop the membrane bonding. Stir the product well and apply it evenly with a brush or roller, then allow it to dry before any further coats. Check the label and Crommelin's full instructions for coverage, coat numbers and drying times before you start, and protect the cured membrane from damage if you will be backfilling against it. Clean tools before the product dries (as a water-based product, warm water is the usual method, but confirm on the pack).
Important notes
Not suitable where it will be exposed to UV or sunlight. It cannot be painted, tiled over, rendered or over-coated, and it is not for trafficable surfaces. If you need a UV-stable option, look at a different Crommelin product. Coverage and cure times depend on the surface and conditions, so treat the listed coverage as a guide and test a small area first.
Specifications
| Brand |
Crommelin |
| Product |
Blackseal Heavy Duty Bitumen Waterproofing Membrane |
| Size |
1L |
| Colour |
Black |
| Base |
Water-based bitumen emulsion, modified with a synthetic rubber co-polymer |
| Application |
Brush or roller |
| Coverage |
Approx. 0.75 m² per 1L (retailer listed, guide only) |
| Dilution |
Up to 50% water to make a bitumen paint |
| Use |
Below-ground and non-UV-exposed exterior areas |
| Not suitable for |
UV exposure, painting, tiling, over-coating, trafficable surfaces |
Safety
The product itself is not combustible, but once the water has evaporated the organic components can burn or break down in a fire. Avoid contact with eyes and skin, keep out of reach of children, and wash off spills and splashes promptly. Refer to the Safety Data Sheet (SDS) for full details.
