Chemical Cleaning & Poultice Systems
Where heat and water aren't enough. Solvent-based removers, degreasers, biocides and drawing poultices, matched to the contaminant and the substrate — the method that gets paint out of porous stone rather than off the top of it.
There's a point on most difficult jobs where physical methods run out. The steam has softened everything it's going to soften, the jetting has lifted everything sitting on the surface, and there's still a red shadow in the sandstone where somebody sprayed a tag. What's left isn't on the wall — it's in it, and the only way to get it out is chemistry.
Chemical cleaning covers a wide range of products with very different jobs: solvent removers that dissolve paint binders, alkaline degreasers that emulsify oil, biocides that kill organic growth at the root, and poultices that draw a stain back out of a porous material over hours or days. Used well, they're precise and gentle. Used badly, they bleach stone, burn mortar, kill planting and end up in a watercourse.
Why porous surfaces need chemistry
Brick, sandstone, concrete and unsealed block paving are full of tiny voids. Spray paint arrives as a fine aerosol under pressure, which is close to ideal for getting into them. The pigment travels below the surface and sits there, which is why a tag that has been pressure-washed often looks worse afterwards — the surface has been cleaned and abraded, and the colour underneath is now more visible against it.
A remover works by breaking down the binder holding the pigment together so it can be flushed back out of the pore structure. Different paints need different chemistry: cellulose car paint, acrylic aerosol, emulsion thrown from a bottle and bituminous paint all respond to different products, and the wrong one simply won't work no matter how long you leave it on.
This is the single biggest reason to call somebody before attacking graffiti yourself. Most DIY attempts drive the pigment deeper or abrade a patch into the wall that is more permanent than the tag was. Cleaning a failed attempt is consistently harder than cleaning the original.
How a poultice works
A poultice is the technique people are least familiar with and it's often the one that saves a job. It's an absorbent paste — clay or cellulose based, carrying the active chemical — applied thickly over the stain and covered so it can't dry out.
As it slowly dries, it pulls moisture out of the substrate, and the dissolved stain comes with it. The staining migrates upwards into the poultice rather than downwards into the material. When it's fully dry, the poultice is peeled or scraped off and the stain leaves with it. On heavy oil or old paint, we may apply it two or three times, each pass drawing out a little more.
It's slow — a single application can sit on a wall for anything from several hours to a couple of days — but for deep staining on stone it's frequently the only method that works without removing the face of the material. On listed and heritage buildings it's often the only method that will be permitted at all.
- Deep paint staining in sandstone, limestone and soft brick
- Oil and diesel in concrete, flags and block paving
- Rust runs from railings, fixings and cramps into masonry
- Carbonate and lime staining where an acid wash would be too aggressive
Got a stain nothing has shifted?
Send us a photo of the surface and the staining. We'll tell you whether it's a poultice job, a remover job, or something that genuinely won't come back to new.
Testing, and why we always do it
No product goes onto an elevation before it has gone onto a test patch. We pick somewhere discreet — behind a downpipe, low on a return wall, a spare paving unit — and try the mildest option that stands a chance first, then escalate only if we need to.
That sequence matters because chemicals can change a surface as well as clean it. Acids etch limestone and lift the surface off polished granite. Strong alkalis can bleach some sandstones and burn lime mortar. Solvent removers can soften a coating you didn't know was there. A test panel tells us all of that for the price of ten minutes, and it gives you something concrete to approve before we commit.
We work through a documented COSHH assessment for every product on site, and we're happy to supply the data sheets in advance for a site induction, a school or hospital estate, or a principal contractor's permit system.
Containment, neutralising and the environment
Chemical cleaning creates chemical run-off, and how that's handled separates a professional job from a cheap one. Before we start we identify the drainage, protect the gullies, and sheet or bund anything that needs it — planting beds, a canal towpath, a play surface, a car park with an interceptor.
Products are neutralised after use rather than simply rinsed, so what leaves the wall is inert by the time it reaches the ground. On sensitive sites we recover the water entirely. The North West has a great deal of water in and around its urban areas — canals, culverted brooks, the Irwell and the Mersey catchments — and surface water drains in these areas frequently discharge straight into them.
Chemical-free where we can, chemical where we must
Our default is the gentlest method that will actually do the job. On a great many jobs that means chemical-free cleaning or steam and nothing else, which is simpler for everyone — no COSHH paperwork, no containment, no neutralising, no residue near a playground or a food premises.
But there's no virtue in refusing to use chemistry when chemistry is what the job needs. Being told a stain is 'permanent' usually means whoever looked at it didn't have the right product or the patience for a poultice. We'd rather do it properly and manage the controls than leave a shadow on a client's building.
When We Use It
Best suited to
- Paint and graffiti that has soaked into porous brick, stone or concrete
- Oil, grease and diesel staining drawn out of the substrate
- Heavy organic growth, where a biocide does the work over days
- Rust, carbonate and mineral staining that water won't touch
Where we'd use something else
No method suits everything. These are the jobs we'd steer away from it.
- Situations where run-off can't be contained or neutralised
- Surfaces with unknown or fragile coatings, without a test panel first
- Jobs where a mechanical or heat-based method would do the same work more simply
Equipment we use
- Graduated graffiti removers, from mild gels to solvent-based strippers
- Alkaline degreasers and emulsifiers for oil, grease and traffic film
- Clay and cellulose-based drawing poultices for deep staining
- Biocides and algaecides for organic growth and spore kill
- Neutralisers, containment and full COSHH assessments for every product used
Surfaces We Use It On
Services That Use This Method
Frequently Asked Questions
Are the chemicals you use safe around the public, children and pets?
The products are controlled substances used by trained operatives under a COSHH assessment, with the working area cordoned during application and the surface neutralised and rinsed before it's handed back. Once that's done the area is safe to use normally. On school, nursery, healthcare and playground sites we default to the mildest effective option and will often use chemical-free or steam methods instead.
How long does a poultice take?
Anything from a few hours to a couple of days per application, depending on the stain, the substrate and the weather — it has to dry slowly to work. Deep oil or old paint staining may need two or three applications. It's not a quick method, but for stains that have penetrated a porous surface it's usually the only one that genuinely removes them.
Will chemical removal leave a clean patch that stands out?
It can if it's done carelessly — a small, aggressively cleaned area on a dirty elevation will read as a bright patch. We manage that by feathering the clean outwards and, where the contrast would be obvious, cleaning to a natural break such as a pier, a bay or a string course so the edge falls somewhere the eye expects it.
Can you remove graffiti without damaging the paint underneath?
Often, yes — on a sound, modern paint system a mild gel remover will lift aerosol without attacking the coating beneath, and we'll prove it on a test patch first. On older or unknown coatings there's a real risk the remover takes both, in which case the honest answer is that the panel needs repainting, and we'll tell you that before we start rather than after.
Our Other Cleaning Systems
Need graffiti gone — fast?
Call 0161 399 5247 or request a free quote. We respond within one working hour.