About STP Industrial Bitumen (Oxidised / Blown Grade)

STP Industrial Bitumen is the oxidised, or blown, class of bitumen rather than the paving grade used on roads. It is made by blowing hot air through molten penetration-grade bitumen under controlled temperature, which drives a polymerisation reaction inside the material. The result is a binder with a markedly higher softening point, lower penetration and a tougher, more rubbery character than the feedstock it started from. Depending on grade the consistency runs from highly viscous to effectively solid at room temperature, and it is this hardness-plus-heat-resistance combination that makes it the workhorse binder of the roofing, waterproofing and industrial-coating trades.

The product is designated under IS 702, the Bureau of Indian Standards specification for industrial bitumen, using the familiar two-number grade system — 85/25, 90/15, 95/5 and similar. The first figure is the mid-point softening point in degrees Celsius and the second is the mid-point penetration in tenths of a millimetre at 25 degrees C, so a higher first number and a lower second number mean a harder, more heat-stable grade. Space Arc Engineering supplies STP Industrial Bitumen as an authorised project distributor across Delhi NCR and Pan-India, helping contractors and fabricators match the right grade to the job rather than defaulting to whatever drum is on hand.

The technical insight

The whole point of oxidising bitumen is to move its softening point well above the temperatures a roof or pipe will ever see in service. Ordinary paving bitumen begins to flow and sag in the 45–55 degrees C range — fine buried in a road, useless on an exposed terrace felt that can touch 70 degrees C on an Indian afternoon. Air-blowing reorganises the asphaltene and maltene fractions and lifts the softening point into the 85–155 degrees C band depending on grade, while simultaneously cutting penetration so the film is harder and less prone to creep. That is why grade selection is not cosmetic: an 85/25 stays workable and slightly flexible for bonding felts, whereas a 95/5 or 115/15 is chosen where you need a rigid, near-solid coating that will not move under load or heat. Because the material is chemically stable, fully water-resistant and inert to most dilute acids and alkalis, the same cured film that keeps water out of a roof also protects a buried steel pipe from soil corrosion for decades.

Where it is used

• Manufacture of bitumen roofing felts and built-up membrane systems
• Hot bonding of bituminous felts to the deck and to each other in multi-ply roofing
• Anti-corrosive coating and wrapping of buried and exposed steel pipelines
• Protective and insulating coating over electrical cables and cable joints
• Sound-deadening felts and automotive underbody sealing compounds
• Base binder for industrial bituminous mastics, jointing and sealing compounds
• Waterproofing of below-grade structures and tanking where a hot-applied coat is specified
• Flooring mastics and anti-slip bituminous compounds in the piling industry

Key advantages

• High softening point keeps the coating stable on vertical and sun-exposed surfaces where road bitumen would sag
• Completely water-resistant once cured, giving reliable long-term waterproofing
• Chemically stable and inert to most dilute acids and alkalis, ideal for buried pipe protection
• Available across a spread of IS 702 grades so hardness and flexibility can be tuned to the application
• Forms a seamless, monolithic film with no laps or joints to fail
• Economical binder with a very long service track record in Indian roofing and pipeline work
• Bonds strongly to felts, metal and concrete when applied hot to a primed surface
• Supplied to a recognised BIS specification, so incoming material can be checked against grade limits

Limitations & considerations

• Hot-applied only — it must be melted in a boiler and handled at high temperature, which needs trained crews and burn precautions
• Not suitable for road pavement or asphalt-mix work; that calls for paving-grade bitumen to IS 73
• Being oxidised and harder, it is less elastic than modified-bitumen or APP/SBS membranes and can become brittle under sharp thermal cycling if a very hard grade is used where flexibility is needed
• UV-exposed films weather over time and are usually protected with a reflective or aluminium coating on roofs
• No cure-time or coverage figure can be quoted generically — consumption depends entirely on film thickness, substrate and grade, so it must be established on site
• Overheating during melting degrades the bitumen and lowers performance, so boiler temperature must be controlled to the grade

Selection & best practice

Specifications

Industry use cases

How we position STP Industrial Bitumen (Oxidised / Blown Grade)

STP Industrial Bitumen is the raw, hot-applied binder end of the waterproofing range — best where a fabricator or contractor is building up felts, coating pipe or making compounds and wants full control over grade and film. Buyers who want the same bituminous protection without a boiler should look at STP’s own finished-membrane line, including its APP-modified SuperThermoLay torch-applied membranes, which use oxidised-bitumen technology in a factory-made sheet. From our other brands, Fosroc’s cold-applied liquid systems are the natural alternative for roofs and terraces where hot work is impractical. For grades and project quantities across Delhi NCR and Pan-India, Space Arc Engineering supplies and advises as an authorised STP distributor.

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