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Bitumen Trowel Mastic - Black Jack (903) - 5 Litres

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Bitumen trowel mastic is a trowel applied black heavily filled bituminous compound with added fibres for reinforcement. The product forms a surface skin, but the mass below remains soft to allow for moderate movement. Suitable for sealing and filling holes in mastic asphalt, roofing felt, corrugated iron, metal guttering and downpipes.

Black jack bitumen mastic is ready for use and should not be thinned. Apply by steel trowel or putty knife.

Cracks and holes

Force the compound into the crack, but finish with a 25mm band at a 3mm thickness running the length of the crack. For large cracks and holes, apply the compound over the area to be treated and embed a closely woven glass fibre membrane into the compound to overlap the crack or hole by 50mm. Allow to dry  and then apply a second coat, fully covering the reinforcing membrane.

Corrugated iron/fibre cement sheeting

Tighten loose hook bolts and trowel around with mastic. Remove loose screws, re-bed  screws and washers in black jack bitumen mastic and tighten. Top seal in further mastic and trowel to a smooth finish. If the sheet is cracked, clean and prime with black jack bitumen/flashing primer and apply a bandage strip of glass fibre embedded in the mastic. When dry, overcoat with black jack bitumen/flashing primer followed by black jack bitumen paint. Use the same technique for sealing side and end laps in corrugated sheeting.

Point up butt edges of ridge tiles, fillets and slates with black jack bitumen mastic.

Lead and zinc
Trowel over cracks and pinholes, where necessary, reinforcing with a woven glass membrane, fully embedded and covered.

Re-adhere loose felt using black jack roof felt adhesive. Apply black jack bitumen mastic and overcoat with black jack all weather coating.

Please note felt must be completely dry before applying the mastic.

Surface preperation
As with all surface coatings, preparation of the surface is of great importance and will influence the degree of adhesion obtained and the life of the coating, All surfaces must be sound, stable and thoroughly clean and dry.  Metal surfaces should be wire brushed to remove rust.  Where long term protection is required an initial treatment of a rust inhibitive product such as red lead or zinc phosphate should be used. Loose or blistered paint should be removed. New galvanised surfaces should be roughened with a wire brush or treated with a proprietary etch primer. If the surface is still dusty after preparation, or coated in weathered bitumen, prime with black jack bitumen primer and allow to dry.

To assist in cold weather application, store the material in a warm room overnight prior to use.

Areas for use
Mainly used for :

  • Waterproofing, stopping, bedding, bonding and sealing.
  • Adheres to/fills holes in: mastic asphalt, roofing felt, corrugated iron, cast iron, fibre cement, slates, lead, copper, zinc, concrete and timber.

3 litres per m2 - giving 2mm wet thickness.

Drying time
24 hours to develop a surface skin, the mass below remaining elastic for many months.

Black jack bitumen mastic contains a flammable solvent, and all normal precautions against fire must be taken during both storage and use.  Store in original container in cool dry conditions.  Keep away from sources of ignition.

Shelf life
24 months from date of manufacture in undamaged containers.

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