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Outdoors

Where cleaning has a weather window, where the effluent goes somewhere, and where the finish rather than the dirt sets the limit.

Outdoor cleaning differs from indoor cleaning in four ways this catalogue can evidence. It has a WEATHER WINDOW: the conservation procedure for outdoor bronze specifies a bright, dry, warm day, because water and solvent must evaporate quickly for the work to succeed at all. It has a SUBSTRATE PROBLEM that indoor work does not — whatever is being cleaned sits on something else, and the same procedure floods the masonry beneath the plaque with clean water throughout, so that cleaning effluent is not absorbed by the wall. It has a WATER SUBTLETY that reverses an assumption: de-ionised or distilled water is MORE aggressive for cleaning than tap water, and for that reason must not be used on polished stone, marble, limestone or concrete, where it can cause slight surface etching. And it has PROTECTION AS PART OF THE JOB, because there is no roof — the wax that goes on after the cleaning is the thing that determines when the next cleaning is needed. Two of the register's outdoor materials are soft and porous, which is why pressure washing is the wrong tool on garden stone even where it suits paving.

What this setting actually gets

  • Moss and lichen — Three different organisms treated as one green problem. Where they grow tells you more about the fix than any product does.

What suits it here

Recorded as appropriate to this setting rather than cleared on a material. Suitability in a place and safety on a surface are separate questions, and both have to pass before anything is recommended.

  • Protective waxing

    Not a cleaning step but the step that makes the cleaning survivable — and cleaning removes the coating, so skipping it leaves the surface worse off.

  • Rinsing and drying

    The step people skip, and the one that decides whether cleaning protected the surface or damaged it. Residue left behind is exposure that continues after you stop.

What to keep out of it

  • Pressure washing — Not a prohibition on pressure washing outdoors, which is where it belongs — a caution that the outdoor material set includes soft porous stone and old mortar, for which it is the wrong tool even where it suits the paving next to it.

Precautions this setting adds

  • Mould remover

    • Ventilate the area
    • Wear gloves
    • Wear eye protection

    Windows open during and after, and doors shut so spores are not carried to other rooms. Mask, gloves and goggles, washed or safely discarded afterwards.

Why this setting is different

  • Water purity and aggressiveness — Purer water is a stronger solvent, not a gentler one. It cleans metal better and etches carbonate stone, and both facts have the same cause.

A context page states what changes in a setting. What is safe on a given surface is answered on the material, and what to do about a given problem is answered on the stain — because both of those travel between settings and the answers on this page do not.