TORC System Cleaning (2026): Guide for Listed Buildings

TL;DR

TORC system cleaning is a low-pressure vortex technology that combines air, fine granulate, and a small amount of water to remove graffiti, carbon deposits, and paint from stone, brick, and other surfaces without causing damage. Developed by Stonehealth Ltd, it evolved from the earlier JOS system and is now the method most frequently specified by conservation officers for cleaning listed buildings and heritage structures across the UK. It uses as little as 25 litres of water per hour and operates without electricity, making it both gentle and practical for sensitive sites.

What Is TORC System Cleaning?

TORC system cleaning is a conservation-grade surface cleaning method that uses a swirling vortex of low-pressure air, fine inert granulate, and minimal water to lift contaminants from building surfaces. Rather than blasting dirt away with high pressure or dissolving it with harsh chemicals, the TORC system works through gentle particle action at the nozzle tip. The vortex carries tiny granulate particles across the surface in a controlled swirl, dislodging everything from decades-old carbon crusts to fresh graffiti paint, without eroding the substrate underneath.

The system was developed by Stonehealth Ltd, a Gloucestershire-based manufacturer that has been shaping conservation cleaning standards since the company was incorporated in 1989. Stonehealth first introduced the JOS gentle swirling vortex system in the mid-1980s, which transformed building cleaning by replacing destructive methods like sandblasting and chemical flooding. In 2000, they launched the TORC system with modularised nozzles that delivered even more precise control and cleaning efficiency.

The TORC system is the method most frequently approved and specified by Conservation Officers and Historic England for use on delicate heritage structures. It is also one of the most effective tools available for removing graffiti from stone and brick without ghosting or discoloration.

If you’ve seen TORC mentioned in a contractor’s quote or a conservation officer’s specification, it refers specifically to this Stonehealth technology, not a generic cleaning approach.

How the TORC System Works

Understanding the mechanism matters because it explains why TORC cleaning is so much gentler than conventional methods while still being effective against stubborn contaminants.

Here’s the sequence:

1. An air compressor generates airflow at 6 to 8 bars of pressure (125 CFM minimum).
2. A pressure pot (weighing approximately 65kg) holds the chosen granulate.
3. An air-powered pump and cooler feed air through the system. A key feature: no electrical supply is needed. Stonehealth’s air-powered pump upgrade eliminated the need for mains electricity, making TORC easier to deploy on scaffolding, in churchyards, or at remote heritage sites.
4. A hose delivers the air, granulate, and water to an interchangeable nozzle.
5. At the nozzle tip, the three elements combine into a swirling vortex that moves across the surface in a controlled pattern.

The operator independently adjusts air pressure, water flow, and granulate feed rate. This three-variable control is what makes TORC system cleaning so adaptable. Sensitive limestone might require just 1 to 2 bars of pressure with a fine granulate, while heavy industrial carbon on granite could call for the full 8 bars with a coarser medium.

Key Technical Specifications

Parameter	Value
Air pressure	1-2 bars (sensitive) to 8 bars max
Water flow	0.5 to 1.5 L/min (max ~60 L/hr)
Nozzle apertures	5mm, 7mm, 9mm, 11mm, 13mm
System dry weight	~200kg (standard)
Operating temperature	5°C to 35°C
Noise at nozzle	~99 dB

The nozzle sizes serve different purposes. A 5mm aperture is chosen for fine architectural detail, carved mouldings, or delicate conservation work. An 11mm or 13mm nozzle covers large ashlar blocks or expansive facades more efficiently. This range of options is part of what makes TORC cleaning appropriate for everything from graffiti removal on historic buildings to routine facade maintenance.

The Three Granulate Types

Most articles about TORC cleaning mention “fine granulate” and leave it at that. In practice, the granulate choice is one of the most important decisions an operator makes. Stonehealth supplies three approved types, each suited to different contaminants and substrates.

Granulate	Source	Mohs Hardness	Micron Size	Best For
Calcite	Marble-derived calcium carbonate (CaCO₃)	3.0-3.5	~250	General carbon removal from most masonry types
Dolomite	Natural mineral	~3.5-4.0	Varies	Paint residue removal from stone surfaces
Unil	By-product of coal-burning power stations	6.5	80, 180, 250, 500	Heavy carbon, aged paint on robust substrates

Calcite is the workhorse. Its semi-angular crystallised form makes it effective against carbon deposits on almost all types of masonry without scratching softer stones. Dolomite is selected specifically when paint residues need to come off stone. Unil, with its significantly higher hardness rating of 6.5 on the Mohs scale, handles the tough jobs: heavy industrial carbon, old oil-based paints on hard stone, and thick bituminous deposits.

Unil’s four micron grades add another layer of precision. The 80 and 180 micron grades, combined with a smaller nozzle and the TORC Studio system, deliver conservation-grade delicacy for the most sensitive work. At the other end, the 500 micron grade tackles aged paint on robust substrates where gentler media would be too slow.

For graffiti removal specifically, the granulate selection depends on the paint type and the substrate. Aerosol graffiti on Portland stone calls for a different approach than oil-based paint on brick. A trained TORC operator will run a test patch to determine the right combination before committing to the full surface.

What Does TORC System Cleaning Remove?

The range of contaminants TORC handles is broader than many people expect:

• Graffiti paint, including oil-based, aerosol, and cement-based formulations
• Carbon sulphation, the black crusting caused by decades of air pollution reacting with limestone and sandstone
• Limescale and efflorescence
• Old paint layers, both oil-based and water-based
• Bitumen (when oxidised)
• Smoke and soot damage
• Biological growth, including moss, algae, and lichen
• Bird fouling
• Oxidation from bronze, brass, copper, and anodised aluminium

Carbon sulphation deserves special mention. Portland stone facades, like those on St Paul’s Cathedral or government buildings along Whitehall, accumulate black crusts over decades as sulphur dioxide in polluted air reacts with the calcium carbonate in the stone. TORC’s fine granulate cuts through these crusts in a way that steam-based methods alone often cannot manage.

Surfaces Compatible with TORC Cleaning

TORC system cleaning works across a wide variety of substrates:

• Natural stone: limestone, sandstone, granite, marble, slate
• Brick and terracotta
• Concrete
• Ceramic tiles and faience
• Glass (though dedicated glass graffiti removal methods are often more appropriate for shopfronts)
• Metals: bronze, brass, copper, anodised aluminium
• Render and stucco

The system’s ability to clean metals is often overlooked. Bronze statues, brass plaques, and copper cladding all develop oxidation and patina that TORC can remove or reduce without pitting the surface.

For graffiti on brick, TORC is particularly valuable because brick’s porous nature makes it vulnerable to ghosting when aggressive methods are used. The vortex action lifts paint from the surface and from within pores without opening them up further.

TORC vs DOFF Cleaning: Key Differences

Both TORC and DOFF are manufactured by Stonehealth, and they’re frequently mentioned together in conservation specifications. But they work in fundamentally different ways and are suited to different problems.

Factor	TORC	DOFF
Mechanism	Particle-based vortex (air + granulate + water)	Heat-based (superheated steam, up to 150°C)
Water consumption	~25 L/hr typical (60 L/hr max)	~300 L/hr
Primary strengths	Carbon, mineral deposits, paint, graffiti	Biological growth (moss, algae, lichen), paint
Kinetic action	Yes, granulate provides physical cleaning action	Minimal, relies on thermal energy
Electrical supply needed	No	Yes

The core distinction: TORC is particle-based, DOFF is heat-based. This means TORC excels at removing hard, adhered residues like old paint layers, bitumen, cement splashes, and limescale. DOFF’s thermal action often lacks the kinetic power to break these mineral-based bonds, but it is superior for killing and removing biological growth at the root.

Combined DOFF and TORC Workflows

Experienced conservation contractors frequently use both systems on the same project. The typical sequence is DOFF first to clear organic matter (algae, moss, lichen, biological staining), followed by TORC to address the embedded mineral deposits, carbon, or graffiti underneath. This combined approach delivers comprehensive facade restoration that neither system could achieve alone.

The water consumption difference is significant for practical reasons too. TORC’s low water use (roughly 25 litres per hour versus 300 for DOFF) means less moisture absorption into porous stone, which reduces the risk of frost damage in colder months and minimises drying time.

For a detailed breakdown of the companion system, see our guide to DOFF brick cleaning.

Why TORC Is Preferred for Heritage and Listed Buildings

Conservation officers and Historic England frequently specify TORC cleaning for Grade I and Grade II listed buildings, and for good reason. The system’s low-pressure operation, minimal water use, and adjustable granulate options mean it can clean without removing the surface “skin” of aged stone, preserving what conservators call the patina of age.

The list of notable UK buildings cleaned with TORC reads like a heritage greatest hits: Buckingham Palace, Canterbury Cathedral, Westminster Abbey, Hampton Court Palace, the Tower of London, St Pancras station, Harrods, and buildings across Oxford and Cambridge universities.

Three characteristics make TORC system cleaning particularly suited to heritage work:

Low water volume. Porous historic stone absorbs water readily. Excess moisture can cause salt crystallisation damage, freeze-thaw cracking in winter, and staining. TORC’s maximum of 60 litres per hour (and often much less) keeps moisture ingress to a minimum.

Adjustable aggression. The operator can dial pressure down to 1 to 2 bars for the most sensitive substrates, using calcite granulate through a 5mm nozzle. This level of control simply doesn’t exist with pressure washing or chemical cleaning.

No chemicals required. The cleaning action is purely mechanical. No chemical residues are left in the stone to cause future reactions or staining.

When graffiti appears on a listed building, the stakes are particularly high. Aggressive removal methods risk ghosting (a permanent shadow of the graffiti visible in the stone), pitting, and surface erosion. TORC avoids these problems.

If your property is listed or in a conservation area and has been vandalised, specialist listed building graffiti removal ensures both the graffiti and the method used are properly handled.

TORC for Graffiti Removal: How It’s Applied

This is where TORC system cleaning connects most directly to the real-world problem of graffiti on heritage stone and brick. While every ranking page for this topic focuses on general facade cleaning, TORC’s graffiti removal capability is arguably its most practically important application for property managers in London and other urban areas.

The Graffiti Removal Workflow

A trained TORC operator follows a specific sequence when removing graffiti from sensitive substrates:

1. Site survey and substrate identification. The operator assesses the stone or brick type, the graffiti medium (aerosol, marker, oil-based paint), and the surface condition.
2. Test patch. A small, inconspicuous area is cleaned first to confirm the right combination of granulate, nozzle size, and pressure. This step is non-negotiable on heritage buildings.
3. Chemical pre-treatment (if needed). Deeply penetrated graffiti, particularly aerosol paint that has soaked into porous substrates, may require a chemical softener applied before TORC cleaning. This loosens the bond between paint and stone so the vortex can lift it cleanly.
4. TORC vortex cleaning. The operator works across the affected area at the pressure and granulate settings confirmed during testing.
5. Final surface check. The cleaned area is inspected for residual staining, ghosting, or any substrate change.

On softer substrates like render or stucco, the workflow may lean more heavily on chemical pre-treatment, with TORC used at very low pressure for the final clean-up rather than as the primary removal tool.

Why TORC Prevents Ghosting

Ghosting happens when a cleaning method removes the top layer of stone along with the graffiti, leaving a clean patch surrounded by naturally weathered stone, or when paint pigment is driven deeper into pores rather than lifted out. TORC’s vortex action lifts contaminants away from the surface rather than pushing them in, and its low-pressure operation avoids eroding the stone surface. This is why it consistently delivers clean results without ghosting or discoloration.

Practitioners on YouTube walkthroughs of heritage stone cleaning with TORC consistently demonstrate how the system can clean right up to carved details, window surrounds, and decorative mouldings without softening edges or removing tooling marks. This precision is simply not achievable with pressure washing.

Choosing a TORC Cleaning Contractor

Not everyone claiming to use TORC actually has genuine Stonehealth equipment or trained operators. This is a real and growing problem.

The Rosette Approved Contractor Scheme

Stonehealth operates a Rosette Approved Contractor scheme that sets clear standards for operators. To qualify, contractors must:

• Complete full training, reviewed annually
• Use only genuine Stonehealth parts and materials
• Submit to annual inspection and servicing of all machinery
• Provide at least two customer testimonials per year to maintain Rosette status

Brian Crowe, Stonehealth’s founder, has publicly warned about impostor operators using non-genuine equipment. His concern is direct: “If damage is done, it’s irreversible. If you remove the surface of stone or brick then you can’t get it back.”

What to Verify Before Hiring

When evaluating a contractor who claims to offer TORC system cleaning:

• Ask to see their Rosette ID card and confirm it’s current.
• Request evidence of a test patch before any full-scale work begins.
• Check whether they also operate DOFF, as many projects benefit from the combined workflow.
• Confirm they carry appropriate insurance for heritage work.
• Ask whether they’ve obtained or will help obtain conservation officer approval if the building is listed.

Discussions on heritage forums and among property managers consistently flag that verifying contractor credentials is one of the most important steps in protecting a historic building. The equipment is not consumer-grade and is not something that can be rented from a tool hire shop. Only Stonehealth-inducted and authorised operators may use the TORC system.

Need a contractor who is equipped for heritage-safe graffiti removal using TORC and DOFF systems? Get in touch with the specialists for a free quote.

Limitations and Practical Considerations

No cleaning method is perfect for every situation, and acknowledging TORC’s constraints helps set realistic expectations.

Temperature restrictions. The system cannot operate below 5°C ambient temperature, which can be a scheduling factor for outdoor heritage projects during winter months.

Noise levels. At approximately 99 dB at the nozzle position, TORC is loud enough to require hearing protection for operators and may need site management planning in residential areas or near schools and hospitals.

Pre-treatment may be necessary. Deeply saturated graffiti, particularly aerosol paint that has penetrated porous substrate over days or weeks, often requires chemical softener application before TORC cleaning can fully remove it.

Conservation officer approval. On listed buildings and structures in conservation areas, any cleaning method, including TORC, typically requires prior approval from the local conservation officer. Starting work without this approval can result in enforcement action.

Speed trade-off. Heritage-safe methods prioritise substrate preservation over speed. TORC system cleaning on a delicate limestone facade will take longer than pressure washing would, but the results are incomparably better and the stone remains intact.

Not a DIY method. The equipment weighs approximately 200kg, requires a suitable compressor, and demands trained operation. This is professional-grade conservation technology.

For situations where the wrong method has already been applied and damage needs assessment, or where multiple types of vandalism need different approaches, it’s worth understanding when to call a professional.

Frequently Asked Questions

What is the difference between TORC and JOS cleaning?

TORC is the evolution of the JOS system. Both were developed by Stonehealth and use the same swirling vortex principle. The JOS system launched in the mid-1980s, while TORC arrived in 2000 with modularised interchangeable nozzles that improved control and efficiency. TORC also uses less water (approximately 25 to 60 litres per hour compared to about 45 litres per hour for JOS) and the air-powered pump upgrade means no electrical supply is needed.

Can TORC system cleaning remove all types of graffiti?

TORC is effective against most graffiti types, including aerosol, oil-based paint, and cement-based paints. However, deeply penetrated graffiti on very porous substrates may require chemical pre-treatment before TORC cleaning to soften the paint bond. Acid-etched graffiti on glass is a completely different problem that requires specialist restoration techniques rather than TORC.

Is TORC cleaning safe for all types of stone?

Yes, when operated correctly. The system’s adjustable air pressure (as low as 1 to 2 bars), multiple nozzle sizes, and three granulate options with different hardness ratings allow operators to calibrate the clean for each specific stone type. A test patch should always be carried out first, particularly on soft or weathered substrates.

How much does TORC cleaning cost?

Costs vary depending on the surface area, contaminant type, accessibility, and whether listed building approvals are needed. Because the system requires trained operators and specialist equipment, it costs more than basic pressure washing. But for heritage buildings, the cost of repairing damage from the wrong cleaning method far exceeds the premium for using TORC.

Does TORC cleaning damage mortar joints?

No. One of TORC’s advantages over high-pressure washing is that its low-pressure vortex action does not erode mortar joints. High-pressure washing can blast out soft lime mortar from historic brickwork, leading to expensive repointing. TORC avoids this problem entirely.

Can I hire a TORC machine and do it myself?

No. Stonehealth restricts the use of TORC equipment to trained and authorised operators. The machines are not available for consumer hire. This policy exists to protect both the equipment’s reputation and, more importantly, the buildings being cleaned. Improper use could cause irreversible surface damage.

How long does TORC system cleaning take?

This depends on the surface area, the type and thickness of contamination, and the sensitivity of the substrate. A single graffiti tag on hard stone might take under an hour. A full facade cleaning project on a listed building could take days or weeks. Heritage-safe methods are inherently slower than aggressive alternatives, but the results justify the time.

Should I apply anti-graffiti coating after TORC cleaning?

For buildings in areas prone to repeat vandalism, applying an anti-graffiti coating after TORC cleaning is a smart preventive step. These coatings create a barrier that makes future graffiti far easier and faster to remove, often without needing TORC again for subsequent incidents.