Mobile Shot Blasting London, Kent, Surrey & Sussex

Frequently Asked Questions

• What is the difference between shot blasting and sandblasting?

  Although the terms are often used interchangeably, shot blasting and sandblasting are distinct processes.

  Shot blasting propels abrasive media (such as steel grit, shot or other approved particles) at high velocity using either compressed air or a centrifugal blast wheel. Sandblasting traditionally refers to the use of silica sand as the abrasive medium, delivered via compressed air.

  The use of silica sand is now heavily restricted in the UK due to the risk of silicosis, a serious lung condition caused by inhaling fine silica dust. Shot blasting with modern, approved media is generally safer, more controllable, and produces a more consistent surface profile for coating adhesion.

• What surfaces can be shot blasted?

  Shot blasting is suitable for a wide range of surfaces including steel, iron, concrete, brick, stone, timber and fibreglass.

  The key variable is selecting the correct blast media and pressure for the material in question. Harder, denser media such as steel grit is suited to robust surfaces like structural steel, whilst softer media (such as crushed walnut shell or sodium bicarbonate) is appropriate for more delicate substrates like timber or fibreglass, where surface damage must be avoided.

  Using the wrong media or incorrect pressure can cause irreversible damage, which is why experienced operators are absolutely essential.

• What does dustless shot blasting mean, and why does it matter?

  Conventional blasting methods generate significant volumes of airborne dust, posing health risks to operatives and nearby personnel, and causing contamination of surrounding areas.

  Dustless shot blasting equipment (such as the Farrow units we operate) is specifically engineered to contain and capture spent media and debris at source, preventing dust from becoming airborne.

  This makes the process far safer for operatives, suitable for use in occupied or sensitive environments, and reduces post-work clean-up considerably. It also means we can carry out works in locations where traditional blasting would simply not be permitted.

• What is the correct surface profile for painting or coating after shot blasting?

  The surface profile (often referred to as the anchor profile or surface roughness) is critical to the long-term performance of any applied coating.

  Shot blasting creates a textured surface at a microscopic level, giving paint, primers and protective coatings a mechanical key to bond to. The required profile is typically specified in microns and will vary depending on the coating being applied.

  For structural steelwork, a common standard referenced is SA 2.5 (ISO 8501-1), which requires near-white metal cleanliness. Applying coatings to an incorrect surface profile is one of the most common causes of premature coating failure.

• How does intumescent paint actually work?

  Intumescent paint looks and applies much like a conventional coating, but its behaviour under fire conditions is very different. At ambient temperatures it remains chemically inert.

  When exposed to heat above approximately 200°C, a complex reaction occurs within the coating: the binder melts, gases are released, and the paint expands rapidly to form a thick, low-density carbonaceous char layer.

  This char can expand to many times the original paint thickness and acts as a highly effective thermal insulator, slowing the rate at which heat transfers to the steel beneath.

  This buys critical time (typically 30, 60, 90 or 120 minutes depending on the specification) before the steel reaches its critical failure temperature of around 500 to 620°C.

• Why does structural steel require fire protection?

  Despite being non-combustible, structural steel loses a significant proportion of its load-bearing strength when exposed to high temperatures. Unprotected steel can begin to lose structural integrity within minutes of exposure to a severe fire, potentially causing catastrophic building collapse.

  Building regulations and fire engineering specifications therefore require passive fire protection (such as intumescent paint) to be applied to structural steel elements.

  The required fire resistance period (typically expressed as R30, R60, R90 or R120) is determined by the building's use, occupancy, and the fire risk assessment carried out during the design stage.

• What blast media do you use, and are they environmentally safe?

  We use a broad range of blast media, selected to suit each specific job. Options include steel grit and shot for heavy industrial applications, crushed recycled glass, sodium bicarbonate (soda blasting), dry ice, and agricultural materials such as crushed nutshell or corn cob.

  The majority of our media is derived from recycled or naturally occurring materials and is selected with environmental impact in mind. Soda blasting, for example, uses sodium bicarbonate which is entirely biodegradable and non-toxic, making it particularly suitable for environmentally sensitive locations or surfaces that will come into contact with water.

• Can shot blasting be carried out on a live or occupied site?

  Yes, with the right equipment and controls in place. Our mobile Farrow units are specifically designed to contain dust and spent media, making them suitable for use in environments where operations must continue nearby.

  We assess each site individually prior to works commencing, taking into account factors such as proximity to other trades, public access, neighbouring properties, and environmental sensitivity. Where necessary, additional containment measures can be put in place.

  All works are carried out in full compliance with current health and safety legislation, including COSHH regulations.

• How long does intumescent paint last before it needs to be reapplied?

  The service life of an intumescent coating depends on a number of factors including the specific product used, the environment in which it is applied (internal, semi-exposed or fully external), and the quality of the primer and topcoat products used alongside it.

  Internal coatings in a stable, dry environment can last in excess of 25 years. External or semi-exposed applications are subject to weathering and will typically require inspection at more regular intervals.

  Any intumescent coating should be inspected periodically as part of a building's fire safety maintenance programme, and any damage, cracking or delamination should be addressed promptly to maintain the specified fire rating.