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Cement/mortar/concrete There are two stages to removing cementitious stains from paving... STAGE 1 Mechanical action - remove as much of the cementitious material as possible by using a hammer and bolster to chisel off the offending spots of material, fondly referred to as 'snots' in the building trade. Take care not to chisel into the paving, just chisel sufficiently to remove any 'snots'. Scrubbing with a wire brush can remove most of the remaining material without inflicting long-term damage to the paving. The chiselling and scrubbing process may be all that is required to remove the worst of the stain. Natural weathering can eliminate, or render inconspicuous, any remaining slight staining. STAGE 2 Chemical action - this should only be undertaken if the efforts of Stage 1 have left an undesirable or unsightly stain. Be very careful, chemical cement stain removers sold by builders' merchants contain an acid that reacts with the cementitious material, breaking it down and enabling total removal by repeated chemical treatment and scrubbing with a wire brush. If you are attempting to clean concrete flags or concrete blocks, the acid will also attack the surface of the paver, eating away a thin surface of the unit. The same holds true for natural limestone (as in some tarmac) or marble used for paving. Test the action of the acid on a small, inconspicuous area of the pavement. Some pavers can drastically, and irreversibly, change in appearance when treated with acid. If in doubt, leave it! It may be easier to replace the stained paving, assuming it is constructed from small elements, such as blocks, bricks or flags. You MUST wear protective gloves, clothing and most importantly, eye protection when using these acid based cleaners. Read the manufacturer's instructions thoroughly. We dilute most acid cleaners to a strength not exceeding 5% acid to prevent serious discolouration or 'burning' of the paving. Some cleaners may already be diluted to this concentration - read the packaging. Apply the acid cleaner as directed in the manufacturers instructions, and leave it to work for 5-10 minutes. We use an old paintbrush dipped in the acid cleaner to treat small areas. For larger areas, choose a dull or cloudy day to prevent the area being dried too quickly by the sun and pre-wet the area with water to prevent the acid being absorbed by thirsty paving. Scrub with a wire brush and you should see the cementitious material coming free. Wash down with clean water and allow to dry to inspect the results. Repeat if necessary, but no more than is absolutely essential. Do NOT use acid or acid-based cleaners with imported sandstone - see the Cleaning Paving for further information

Removing oil stains There are a number of proprietary oil-stain removers available, but we have not yet found one that works well and removes all of the stain, although some of the commercial cleaning agents supplied by specialist construction chemical companies, can remove most of the stains. Prevention is better than cure, so put a cardboard or wooden 'drip tray' underneath any leaky engines. Note that tarmac will degrade if contaminated with oil or a thin, oil-derived product such as petrol, diesel or hydraulic/brake fluid. This damage can not be treated. You may have to repair or replace seriously affected areas. The sooner an oil stain is treated, the more likely it is to be removed. Use a cloth to soak-up any oil droplets on the surface, but don't smear or rub the oil into the surface. Fresh oil stains can be soaked up by proprietary absorbent materials or even some of the clay-based cat litters, cornflour or talcum powder. Any residue remaining after treating with an absorbent agent can sometimes be removed or ameliorated by scrubbing with a detergent and brush before washing down with water. It may take several attempts for this to work. Clean oil will generally soak into the paving and there will be little evidence of its presence after a few weeks. Dirty oil can be very difficult, if not impossible to completely remove. For more stubborn stains, you could use a degreasing agent or engine cleaning fluid such as Gunk, but always test a small inconspicuous area first for adverse reactions. If the stain is proving impossible to shift, consider replacing the contaminated area of paving. For cleaning oil from plain, trowelled concrete: Here are some tips we've picked up from elsewhere for cleaning concrete. These methods should not be used on coloured, or imprinted concrete, or on concrete pavers, or tarmac. Mix 1 measure of trisodium phosphate with 6 measures of water. Daub this over the stain with a clean, old paintbrush and allow the goo to dry completely before scraping off the dried paste, which should, hopefully, bring most of the oil with it. Rinse the concrete surface and scrub vigorously with a stiff brush and clean water. Prepare a solution of 5% sodium hydroxide (caustic soda - NaOH). Daub it over the oil stain using an old paintbrush and allow it to dry for at least 24 hours. Rinse and scrub with clean water, then repeat as required. Paint white spirit or turps over the stain. Let the solvent evaporate for at least one hour before rinsing with hot, soapy water. Repeat as required.

Removing rust stains Rust stains arise from water running over metal fixtures and fittings then depositing iron particles on the paving and/or from the oxidation (rusting) of iron-rich compounds in the aggregate of the paving. There's also a danger of accidental staining when weed- and mosskillers containing ferric sulphate are applied to lawns and gardens next to paths, patios and driveways. Rust stains are probably the most difficult to remove from most types of paving. Many of the dyes used to colour concrete paving are based on iron oxides, so many chemical agent may affect both the rust and the dyes. The 'patio cleaners' sold at the DIY sheds are based on a hydrochloric acid, and these usually have no effect on rust, although the stronger acid dilutions can sometimes make the stains darker. Due to enormous differences in the type, nature and porosity of any substrate, there are a number of possible 'solutions' that may work. It should be noted that just because a particular 'solution' works well on, say yorkstone flags, that does not mean that it will work on imported stone, or on concrete flags. Similarly, any particular solution may have different effects on wet-cast and pressed concrete flags. Whatever is used, it's best to try it out in a small, discreet area first, as it's impossible to predict just how any of these will react with any given stone or concrete. Lemon Juice - genuine lemon juice, fresh from a lemon, not from a bottle or a plastic imitation lemon. Squeeze directly onto the stained area, allow it to react for 5 minutes or so but don't allow it to dry out. While still wet, scrub the stained area with a nylon/polypropylene bristled brush (an old toothbrush is ideal), working the lemon juice into the surface of the paving. Wash off with plenty of clean water after 5 minutes and repeat as necessary. Vinegar - use a clear or white vinegar (spirt vinegar) rather than a coloured vinegar (malt or balsamic). Some readers of this site have reported that cider vinegar gives good results on some concrete surfaces. Use in exactly the same way as described above. Oxalic Acid - nasty stuff, as it's highly toxic, and it's not easy to find. It's more commonly used in the woodworking trades to bleach or whiten wood, but it is quite effective at removing heavier rust stains from concrete and some types of stone. It may come as a proprietary "rust remover" in which case you should follow the manufacturer's instructions to the letter. The efficacy of these products is highly variable and they MUST be tested on an inconspicuous area prior to use to ensure that the paving is not damaged or discoloured by their use. General purpose concrete cleaners may also help to remove rust stains, but again, they are incredibly variable in effect, and it might be as well to use just a simple detergent and hot water. All this leaves mechanical action as the only non-chemical remedy; vigorous scrubbing with a wire brush can sometimes remove the worst of the staining, as can 'buffing', a process where a hard stone or abrasive is used to 'sand down' the surface of the paving, removing the rust, and revealing a clean surface beneath. As ever, prevention is better than cure. Although rust staining does not pose a threat to the structural integrity of the paving in the way that oils do to tarmac, it can be unsightly and detract from the aesthetics. Removal of rust sources and/or use of drip trays will keep most of the stains off the pavement. If using a mosskiller, then ensure any adjacent concrete surfaces are covered and protected.

Algae, Lichens, Mosses, etc. Most pavements that are not frequently trafficked eventually develop colonies of mosses, lichens, fungi and algae over time, particularly in the predominantly damp climate we have in the British Isles. Again, prevention is better than cure, and regular aggressive brushing with a stiff-bristled broom and/or application of a general purpose weedkiller such as sodium chlorate 2 or 3 times per year will keep colonisation to a minimum, but can never completely prevent it. Proprietary fungicidal washes are available from Garden Centres and these usually need to be applied during dry weather, allowing a few days following application for the fungi to be killed and dried in the sun, before removal by simple brushing. Heavily affected areas are best scraped clean with a shovel or a garden hoe and the detritus removed. A stiff brush will remove the residual loose material and then the pavement can be washed down, sloshing the area with bucketfuls of water, spraying with a hose or, for best effect, cleaning with a power washer. Detergents added to the water can help, and, it has been claimed, addition of Jeyes Fluid will deter the vegetation from returning for a limited period.

Beer/Wine/Soft Drinks Patios are meant to be used to enjoy the garden and that enjoyment is often enhanced with a glass of wine, can of beer or bottle of pop. Inevitably some spillages occur and they should be cleaned at the first oppotunity. Hot, soapy water is usually sufficient to remove these sugar-rich stains. Particularly stubborn stains, such as red wine, may be removed by washing with a weak solution of household bleach (Sodium hypochlorite), but test a small area first.

Chewing Gum Not usually a problem on residential paving, chewing gum is the curse of the pedestrianised shopping centres and some councils employ specialist cleaning staff to keep town centres clean and gum-free. There are proprietary gum-removing and gum-dissolving agents available from cleaning supply companies, although they tend to be quite expensive. Individual 'blobs' can be scraped off the pavement, but this usually leaves some of the gum behind. One successful way of removing gum completely is to use a freezing agent to solidify the gum completely, making scraping more effective. These freezing agents, available from cleaning supply companies, are usually in aerosol form and are sprayed directly onto the gum, allowing a few seconds to take effect before removal.
Steam Clean UK, based near Preston, have a specially developed machine that is used to remove chewing gum from many types of surfaces, including all sorts of paving. Their unique system uses high-temperature, low-pressure steam in conjunction with a non-caustic biodegradable cleaning agent to heat and dissolve the gum, which is then scrubbed with an integral brush unit to reduce the sticky residue to a powder that can be washed away with a hose or pressure washer.
They have cleaning contracts with several large commercial concerns, and can also supply their amazing gizmo for sale or hire. For more information, telephone 01772 628561 or click to email.

Paint Paint stains are treated differently depending on how fresh the stain is. New still-wet stains are best absorbed, not wiped, by a cloth or kitchen roll, and then scrubbed vigorously with hot-water and a detergent. Do NOT use thinners, turps, white spirit or any other solvent as they will serve only to carry the paint deeper into the paving or spread it over the surface. Older, fully dried stains can be scraped off the pavement and the residue removed with paint stripper. However, this should not be used on tarmac or other bituminous surfaces, as the paint stripper can dissolve the binder. In these situations, it's often easier to 'touch-up' small stains with a matt black paint.

Barbecue fat Another curse of garden paving are the small fat splashes that build up around a barbecue. As with the drinks stains discussed above, they should be cleaned as soon as possible with hot, soapy water. Most will naturally degrade over time, but when barbecues are a regular occurrence they can build up and become dangerously slippy if not regularly cleaned. For this reason, we always advise our clients to use a gravel surface around a barbecue, as this can be raked over to present a clean surface or easily replaced in cases of heavy fat contamination.

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