Garden ornament
Soft, porous stone outdoors, which is the worst combination for cleaning: it scratches easily, it traps what lands on it, and it hosts what grows on it.
What not to do
Pressure washer should be avoided for Garden ornament
Best avoided
The available guidance advises against this.
Precautions
- Test on an inconspicuous area first
- Wear eye protection
Evidence
Supported
Sources
Conserve O Gram 15/2: Dusting Guidelines for Stone Objects and Interior Architectural Features
National Park Service, US Department of the Interior · Government or regulator
Relied on for: That soft stones such as marble, limestone, alabaster and soapstone can be easily scratched by improper procedures and that highly porous stones entrap dust. (states this directly)
Cleaning & Maintenance Guidelines — Gardens & Driveways
Marshalls plc · Manufacturer documentation
Relied on for: That power washing used to excess damages a surface and shortens its service life. (states this directly)
Precautions
- Test on an inconspicuous area first
- Dispose of responsibly
- Keep away from children and pets
Start here
What this is, what tends to go wrong with it, and what to do about it.
What tends to go wrong
Three different organisms treated as one green problem. Where they grow tells you more about the fix than any product does.
Why it is difficult: Moisture control and recurrence, Surface roughness
The green film outdoors, and NOT the same organism as the mould indoors. Where it grows is the diagnosis: shade, overhanging trees, or paving that does not drain.
Why it is difficult: Moisture control and recurrence
Mostly textile fibres and skin, held by static as much as by gravity — which is why a dry cloth on a plastic surface makes it worse.
Why it is difficult: Static and dust, Mechanical action and abrasion, Why different surfaces get different dirt, Surface roughness
A seasonal particulate that is part of ordinary dust for most of the year and overwhelms it for a few weeks. Dry removal first, because wet pollen stains.
Why it is difficult: Why different surfaces get different dirt
- Oil and grease on textilevia its material
The stain where the trade guidance switches from water to solvent — and the switch brings a warning the water route does not have.
Why it is difficult: Why oil resists water, Penetration into fibres, Why old stains are harder
- Engine oilvia its material
Not simply an oil. Used engine oil carries combustion soot and metal particles, which is why it marks darker and behaves worse than the oil that went in.
Why it is difficult: Why oil resists water, Penetration into fibres, Why old stains are harder
- Greasevia its material
Fats and oils, which water alone cannot lift. Removed by surfactants, by heat, by solvents, or by alkalis that convert the fat into soap.
Why it is difficult: Why oil resists water, Emulsification
The science behind this: Porous and non-porous surfaces, Water purity and aggressiveness, Capillary absorption, Surface roughness, Etching versus staining
In detail
A garden ornament is usually cast concrete, reconstituted stone, natural limestone or sandstone, and each of those is soft, porous and permanently exposed. The conservation guidance for stone objects is explicit that soft stones — it names marble, limestone, alabaster and soapstone — are easily scratched by improper dusting, and that highly porous stones including sandstone and limestone entrap dust that is then difficult to remove. Outdoors, that dust becomes algae, moss and lichen, and the paving manufacturer's account of those applies: they are prevalent where an area is heavily shaded, under trees, or where water does not drain away, so growth is reporting the position rather than neglect. Three practical rules follow. Pressure washing is the wrong tool on soft stone even where it suits a hard paving slab, because excessive pressure damages paving and soft stone scratches easily. Acid cleaning is material-dependent and destructive on limestone and marble, which are dissolved by it. And ferrous sulphate preparations stain concrete brown, while sodium hypochlorite burns and kills plants, so anything applied outdoors must account for what grows under it.
Related
- Garden ornament is made from Concrete and stone paving
- Garden ornament is made from Limestone
- Garden ornament is made from Sandstone
- Garden ornament is made from Cement and mortar
- Garden ornament is made from Architectural bronze
- Garden ornament is commonly affected by Moss and lichen
- Garden ornament is commonly affected by Algae
- Garden ornament is commonly affected by Dust
- Garden ornament is commonly affected by Pollen
Sources for this page
Sources
Conserve O Gram 15/2: Dusting Guidelines for Stone Objects and Interior Architectural Features
National Park Service, US Department of the Interior · Government or regulator
Relied on for: That soft stones such as marble, limestone, alabaster and soapstone are easily scratched by improper dusting, and that highly porous stones entrap dust that is difficult to remove. (states this directly)
Cleaning & Maintenance Guidelines — Gardens & Driveways
Marshalls plc · Manufacturer documentation
Relied on for: That algae, moss and lichen are prevalent in heavily shaded areas and where drainage is poor, that ferrous sulphate products stain concrete brown, that sodium hypochlorite burns and kills plants, and that limestones and marbles must not be acid cleaned. (states this directly)