HG Mould Spray Review
Format: 500ml trigger spray; foam spray variant also available
Active ingredient: Sodium hypochlorite (~3%) with sodium hydroxide
Price: Typically £5-10 depending on retailer and offers
Dwell time: About 30 minutes; longer for heavy growth
Best on: Walls, tiles, ceilings, window reveals, flat grout
Yes, this is a gel site, and yes, we're reviewing a spray. HG is here because it's the most recommended mould remover in the UK, it consistently tops independent comparisons, and pretending it doesn't exist would make every other recommendation on this site less credible. The useful question isn't whether HG is good. It is. The question is which jobs belong to it and which belong to a gel.
What it is
Roughly 3% sodium hypochlorite plus sodium hydroxide, which is to say bleach and caustic soda, in a spray formulated to cling a little better and wet the surface a little more effectively than the bargain options. One reviewer memorably asked whether the secret is just diluted bleach, and chemically that's not far off. HG's actual edge is consistency: a published safety data sheet, a stable formulation, and a nozzle and viscosity that do what the label promises. Spray, wait half an hour, wipe, done.
Where it beats gel
Coverage. Treating a mouldy wall corner, a run of ceiling above the shower, or a whole window reveal with a gel tube would be slow, expensive and silly. A spray covers a square metre in seconds. On flat and gently angled surfaces where the liquid stays put long enough to work, HG finishes the job before a gel is out of the tube.
The one job it can't do
Vertical silicone sealant with staining inside the bead. The spray runs off in a couple of minutes; the stain needs hours of contact. This isn't an HG flaw, it's physics, and it applies to every spray including this one. That job belongs to Skylarlife or another gel. The full argument is in gel vs spray.
Pros
- The UK benchmark, tops independent tests year after year
- Fast: visible results in about 30 minutes on walls and tiles
- Transparent formulation with published safety data
- Foam variant clings slightly better on tiles
Cons
- Runs off vertical silicone before it can finish
- Strong fumes; needs serious ventilation
- Costs more than Astonish for similar chemistry on easy jobs
Verdict
Buy HG for walls, ceilings, tiles and window reveals. It's the best spray in the UK market and it's not particularly close. Just don't ask it to fix your shower sealant; buy one tube of gel for that and stop fighting physics.