Knowledge

Timber is a floor with a finish on top, and most timber floor problems are finish problems. Water that sits on the surface dulls it, detergent strips it, and a wet mop sends moisture into the joints where the boards move.

A mattress is a sponge with a fabric cover, which is why the standard cleaning method — spray it, scrub it, wet-vacuum it — is also how mattresses end up with mould in the core. The rules are to remove soil dry first and to put as little water in as possible.

When a shower head starts spraying sideways, the holes are not worn out; they are scaled shut. The deposit is calcium carbonate from the water supply, and it dissolves in acid rather than in pressure, detergent or bleach.

A barbecue cleans itself if you let it: heat burns the residue to carbon, and carbon scrapes off. The damage happens afterwards, when a caustic cleaner meets an aluminium hotplate or a wire brush takes the seasoning off cast iron.

A washing machine that smells is not dirty because it washes clothes badly; it is dirty because detergent, softener and skin oils build a biofilm in the places the water does not reach at speed. The drum looks clean, the smell comes from the gasket, the drawer and the filter.

Limescale is calcium carbonate, and it does not respond to bleach. That is the whole frustration in one sentence: people reach for the strongest chlorine product in the cupboard, the porcelain whitens, and the ring at the water line stays exactly where it was.

The reason dog urine smell comes back on a humid day is chemistry, not cleaning effort. Urine contains urea and uric acid salts, and the salts are insoluble in water; when humidity rises they re-crystallise and release the same odour again. Water and detergent rinse the surface and leave the problem in the backing.

Paint splatter on tiles is a race. Fresh paint wipes off with a solvent rag in seconds; cured paint has to be softened, and the tool you use to lift it matters more than the bottle you bought. Ceramic is forgiving, glazed porcelain less so, and a metal blade can scratch both.

Oven glass goes brown in two different places, and they need different methods: the film on the inside face is baked-on grease, while the stain between the panes is vapour that condensed there because the door seal stopped sealing. Treating both with the same bottle is how doors get scratched.