Astonish Mould & Mildew Blaster Review
Format: 750ml trigger spray
Active ingredient: Sodium hypochlorite with sodium hydroxide and surfactants; full ingredient list published
Price: Around £2
Dwell time: Minutes for fresh growth
Best on: Weekly maintenance of showers, tiles and window frames
Astonish is one of the bestselling mould products in the UK for a reason that fits in one sentence: it's £2, it's made in Britain, it publishes its full ingredient list, and it works on fresh mould. That's the review, really. Everything below is nuance.
The job it's for
Fresh surface mould, the light speckling that shows up on tiles, paintwork and around window frames when a room runs damp. Caught early, mould hasn't rooted into anything, and a cheap hypochlorite spray kills and lifts it in minutes. Astonish does this as well as products costing four times more, because at this stage the chemistry is trivially easy and everyone's chemistry is the same.
Where it fits in the system: after you've done a deep treatment with a gel, a quick spray-and-wipe of the danger zones every week or two stops new colonies establishing. That habit, plus the ventilation fixes in our prevention guide, is what breaks the cycle of deep-clean, regrow, repeat.
The job it's not for
Established black staining in silicone sealant or grout. Astonish is a thin liquid; it runs off vertical surfaces in seconds and the stain needs hours. Spraying it at blackened sealant week after week is the most common way people convince themselves "nothing works", when the real problem is format, not formula. That job needs a gel, once, properly.
Pros
- Around £2 for 750ml
- UK-made, full ingredient list published
- Excellent on fresh surface mould
- Cheap enough to keep one in every wet room
Cons
- Useless against established stains in sealant
- Runs off vertical surfaces fast
- Bleach fumes in enclosed shower cubicles; ventilate
Verdict
Buy it, keep it under the sink, and use it little and often. Astonish is the maintenance half of the two-product system this whole site recommends: gel once to clear the damage, £2 spray forever to keep it cleared.