Mould

In detail

Mould is a fungal growth that establishes where there is persistent moisture, and treating it as a stain is the reason it so often returns. Three distinct things are involved. There is the living growth, which a disinfectant can kill. There is the pigment it has deposited, which may remain as a dark mark on grout or sealant after everything living is dead, and which needs a bleaching agent rather than a disinfectant. And there is the moisture that allowed it — condensation, a leak, poor ventilation — which no cleaning product addresses and which guarantees recurrence if it is not fixed. On porous materials such as silicone sealant or grout, growth extends below the surface, so a treatment that visibly clears the surface may leave viable material beneath. Extensive or repeatedly returning mould, particularly where it may indicate a building fault, is a case for professional assessment rather than a stronger cleaner. One removal instruction inverts the obvious move: an extension service permits surface mould on hard flooring to be taken up with a HEPA VACUUM and says explicitly NOT to use a standard one. On leather it brushes the spores off DRY first, before anything wet.

What works

• Ammonia is effective against Mould Supported

  Named by the stone trade for biological staining, with an emphatic warning never to combine it with bleach.

• Detergent is effective against Mould Strongly supported

• Sodium hypochlorite (chlorine bleach) is effective against Mould Disputed

  Recorded as DISPUTED, and the dispute is the answer. Every source read puts moisture control first and physical removal with detergent second; where they part company is whether a bleach step afterwards is worth adding, and at what dilution. See the evidence conflict record.

• Mild abrasion is effective against Mould Supported

  A stiff brush, hot water and household detergent. The mechanical part is the part that does the work, and the authorities say so in that order.

Why

• Mould is explained by Porous and non-porous surfaces
• Mould is explained by Moisture control and recurrence

  Three authorities, same ordering, and none of them starts with a product. The reader asking which spray to buy has asked the second question first.

• Mould is explained by Cleaning, sanitising and disinfecting

  The single most load-bearing sentence in the mould family: DEAD MOULD MAY STILL CAUSE ALLERGIC REACTIONS, so it is not enough to kill it — it must also be REMOVED.

Aftercare and prevention

• Rinsing and drying helps prevent Mould

  With a deadline attached: water-damaged materials are dried within 24 to 48 hours, after which the question stops being how to clean and becomes what to remove.

• Dry soil removal helps prevent Mould

  The manufacturer's own explanation of why its fabric resists mildew: the fabric does not promote growth, and the mildew grows on the DIRT left on it. Remove the dirt and there is nothing to grow on.

Hacks and claims involving this

• Spraying hydrogen peroxide and vinegar in sequence Does not work
• Following bleach with an alcohol sanitiser Does not work
• Vinegar as an all-purpose cleaner Disputed
• Steam cleaning sanitises without chemicals Unresolved
• Using a limescale remover on shower grout Does not work
• Mould needs bleach Does not work
• A hot empty wash cleans the machine Unresolved
• Leaving the washing machine door open Plausible mechanism, untested in this application
• Steam mopping a laminate floor Does not work
• Putting a cleaning block in the cistern Does not work
• Combining bleach and hydrogen peroxide Does not work
• Bleach ruins outdoor fabric Does not work

Where the sources disagree