The microbiology of cleaning
What is actually alive on a surface, why it persists, and why removing what you can see is not the same as removing what is there.
What this area turns on
A federal conservation leaflet contradicts the two beliefs that govern most domestic mould treatment, in consecutive paragraphs. Freezing and heat DEACTIVATE spores without killing them, and spores reactivate when the temperature rises. And killing mould does not eliminate the hazard, because inactive mould still causes reactions in sensitive people. Between them they explain why a treated bathroom sealant regrows on schedule — and why the answer is removal and moisture rather than another bottle.
Assessed and found wanting
Widely repeated techniques in this area that the evidence does not support, or supports only in part.
Spraying disinfectant instead of cleaning
Does not workMarketed as the thorough option, and it is — against organisms. On a dirty surface it can fail at both jobs at once, because soil shields the organisms it is meant to kill.
Freezing kills mould
Does not workWidely believed and specifically contradicted: freezing DEACTIVATES spores without killing them, and warming reactivates what survived.
Killing the mould solves the problem
Does not workThe assumption behind every mould product. A federal agency states plainly that killing mould does not eliminate all health hazards, because inactive mould still causes reactions.
The records
Mould fungi
MicroorganismThe organisms behind the marking. Around 1.5 million species, each with its own conditions — and killing them does not end the exposure they created.
Fungal spores
MicroorganismAlready everywhere, water-repellent, and resistant to drying out. Removing them is not the goal, because it is not achievable — denying them moisture is.
Cellulolytic microorganisms
MicroorganismThe fungi and bacteria that digest cotton, linen and paper by converting the fibre itself into sugar. The damage is not staining, it is the material being eaten.
Keratinophilic fungi
MicroorganismThe fungi that feed on protein fibres. Wool and silk are less susceptible than cotton — which is not the same as being safe from it.
Washing machine microbiota
MicroorganismEstablished communities living on the wet surfaces of a domestic washing machine — which is why the smell returns on a schedule after every treatment.
Kitchen sponge microbiota
MicroorganismThe most-studied surface in a domestic kitchen, and the honest finding is narrow: the published methods clean the sponge and are not claimed to eliminate what is in it.
House dust mites
MicroorganismNot a hygiene failure and not removable by cleaning alone. They live on shed skin in soft furnishings, and humidity governs them more than vacuuming does.
Biofilm
ScienceBacteria that have built themselves a protective matrix and stuck it to a wet surface. It resists disinfectant far better than the same bacteria loose in water.
Organic load
ScienceA disinfectant applied to a dirty surface is spent on the dirt. This is why every professional protocol cleans first and disinfects second, in that order.
Moisture control
MethodThe treatment for mould that is not a cleaning product. Every authority in this register puts it first, and it is the only one that stops the problem recurring.
Three different things routinely sold as one. Cleaning removes soil, disinfecting kills micro-organisms, and each is largely ineffective without the other.
Three operations, one word. Neither implies the other — and the order is not a preference: soil shields organisms from the agent meant to kill them.
Killing the mould solves the problem
Claim or techniqueThe assumption behind every mould product. A federal agency states plainly that killing mould does not eliminate all health hazards, because inactive mould still causes reactions.
Freezing kills mould
Claim or techniqueWidely believed and specifically contradicted: freezing DEACTIVATES spores without killing them, and warming reactivates what survived.