Preparation of mastic

Mastics are used for gluing roll materials on various surfaces and gluing strips of roll materials with multi-layer coatings.

They are used both as coating materials and also as protective coatings. Distinguish between bituminous and tar mastics. Bituminous ones are used for gluing glassine and roofing felt, tarry – roofing and roofing leather. Mastics can also be hot and cold of different brands: hot bitumen roofing – MBK-G-55, MBK-G-65, MBK-G-75, MBK-G-85 and MBK-G-100; tar – MDK-G-50, MDK-G-60 and MDK-G-70. The numbers indicate the melting point. Mastics are prepared from binders (bitumen, tar, sand) and dry fillers: peat chips, chalk, fine asbestos No. 6 or No. 7, ground slag or limestone, wood flour, sifted through a fine sieve. Fillers reduce the brittleness of the mastic at low temperatures, increase its heat resistance, and reduce the consumption of bitumen at low temperatures. It is best to use fibrous fillers – asbestos and wood flour.

For fire safety, the boiler or tank in which the mastic is prepared is recommended to be bricked up with bricks and a heavy, tightly closed lid should be fixed above them. Impurities are removed from the molten bitumen with a net stretched over a wire, or a tin can with holes punched in the bottom and fixed on a long handle. For quick melting, bitumen and pitch are recommended to be put into the tank in small pieces.

Cooking bituminous hot mastic. To prepare 10 kg of mastic, 8.5 kg of oil bitumen H-70/30 (grade 4) and 1.5-1.7 kg of filler are required. The bitumen loaded into the dish for 3/4 of its volume is heated to melting. When it starts to foam, floating impurities are removed from its surface. It is necessary to heat the bitumen until it stops foaming and becomes dehydrated. Filling the fire with water, add a dry filler to the bitumen and mix everything thoroughly. Prepare the mastic 2-3 hours before starting work and use it only when hot.

Preparation of cold mastic. To prepare 10 kg of mastic, you need: 5 kg of BN-90/10 bitumen (grade 5), 3 kg of green oil or exactly the same amount of kerosene and 2 kg of fine filler (preferably asbestos No. 6 or No. 7). Prepare mastic as follows. Bitumen is loaded into the dishes, melted until it stops foaming, remove impurities, fill the fire with water and, with constant stirring, pour green oil or kerosene into the bitumen in small portions, and then (also in small portions) the filler. All this is thoroughly mixed. The prepared mastic is poured into a hermetically sealed container.

Preparation of tar mastic. To prepare 10 kg of mastic, you need: 5 kg of coal tar, 3 – coal sand and 2 kg of filler. Tar is loaded into the dishes, heated and coal tar pitch is added there in small portions. All this is melted and stirred until foaming stops. The surfaced impurities are removed, the fire is extinguished, the filler is added in small portions, mixing everything thoroughly. Tar mastic is used only hot.

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