Slate
The stone that survives what the others do not. A paving manufacturer names it among the materials acid washing leaves unaffected.
In detail
Slate is a fine-grained metamorphic rock that splits into flat sheets along its cleavage, which is why it appears as roofing, paving, hearths and worktops. It belongs to the siliceous family, and it is the most chemically robust stone in ordinary domestic use: a paving manufacturer's guidance names granites, basalts and slates specifically as unaffected by acid washing, in a passage whose whole point is that sandstones and limestones are not. That does not make it indestructible. Slate is soft enough to scratch, its riven surface holds soil in the texture so it needs brushing rather than wiping, and some slates contain iron pyrites that rust out as small orange spots — a defect of the stone rather than a stain on it. The bigger practical risk is finish rather than chemistry. Interior slate is frequently sealed or oiled to deepen its colour, and a cleaner strong enough to be worth reaching for will strip that treatment unevenly, leaving patches that look like damage to the stone when the stone underneath is untouched. Where a slate surface has a finish on it, the finish decides the method.
Properties
Sensitivity
- Acids
- Not applicable
- Alkalis
- Not known
- Chlorine bleach
- Not known
- Abrasion
- Recorded
- Porous
- Recorded
“Not known” means CleaningHQ has not established this, not that the material is unaffected.
Why
- Slate is explained by Porous and non-porous surfaces
Related
- Slate is commonly affected by Moss and lichen
- Slate is commonly affected by Algae
Sources for this page
Sources
Cleaning & Maintenance Guidelines — Gardens & Driveways
Marshalls plc · Manufacturer documentation
Relied on for: That acid washing is material-dependent and that granites, basalts and slates are unaffected by it. (states this directly)
Verification: a person has read the passage relied on.
Read on — General Advice, Power Washing, Acid Washing, Seasonal Maintenance, Sealants, the per-stain sections and Organic Growth. Supports the claim as stated.
Last reviewed by a person on .