Patio & exterior
HG Hagesan Black Spot Remover dupe
Why pay around £24.99 for HG? The bulk active is Sodium hypochlorite 14–15% (industrial / dairy grade) — 64% less per working litre than a typical shelf pack.
From the retail pack to the active and the mix
1 · Retail
HG Hagesan Black Spot Remover
5 litres · £24.99 typical snapshot
Water and surfactants
2 · Active
Sodium hypochlorite
9.5% on the label
7681-52-9NaOCl
Bulk Sodium hypochlorite 14–15% (industrial / dairy grade)
3 · Mix
1:1 with water (yields ~7.5% working solution) + 10 ml washing-up liquid
£1.80 per working litre · 64% less than the shelf pack
- Active
- Sodium hypochlorite
- CAS
- 7681-52-9
- Dupe
- Sodium hypochlorite 14–15% (industrial / dairy grade)
- Saving
- 64% / L
Saving is per litre of working-strength mix versus a typical pack price, not versus the DIY kit total. Shop prices move — always check the listing.
Label teardown
What the pack promises versus what the label chemistry actually is.
The marketing claim
“Dissolves deep-rooted black lichen dots”
The chemical reality
Standard commercial bleach solution sold at five times agricultural merchant prices.
Active vs filler
9.5% Sodium hypochlorite · 91% carrier / filler — Water and surfactants
- Typical retail
- £24.99
- 5 litres
- Estimated active cost
- £11.40
- Scaled from bulk £18.00 / 5 litres
- Indicative markup
- 2.2×
- Snapshot maths, not a live shop price
The Marketing Claim & The Catch
A 5 litres pack of HG Hagesan Black Spot Remover typically retails around £24.99 in patio & exterior. That is a UK shelf-price snapshot for the maths on this page — not a live shop quote or a manufacturer RRP. Listings, sizes and deals move. The marketing line is that you are buying a finished lifestyle product, not a weighed chemical.
On the pack: Dissolves deep-rooted black lichen dots; Restores natural sandstone, slate and granite; and Visible results in 2 hours.
The catch: Standard commercial bleach solution sold at five times agricultural merchant prices.
- “Dissolves deep-rooted black lichen dots”
- “Restores natural sandstone, slate and granite”
- “Visible results in 2 hours”
Proprietary Blend & Dosage Breakdown
The labelled active is Sodium hypochlorite at 9.5%. Everything else in the pack is water and surfactants.
At 9.5% active, most of what you pay for is carrier and packaging. The brand is selling convenience, fragrance and a label — not a uniquely potent molecule.
Branded working strength is whatever comes out of the bottle. The bulk alternative is 15% Sodium hypochlorite 14–15% (industrial / dairy grade), mixed to 1:1 with water (yields ~7.5% working solution) + 10 ml washing-up liquid.
- Labelled active
- Sodium hypochlorite
- 9.5%
- Carrier
- Water and surfactants
- Retail pack
- 5 litres · £24.99
The Active Chemical Alternative (Dupe Stack)
The dupe stack is Sodium hypochlorite 14–15% (industrial / dairy grade) at 15% bulk. Indexed as CAS 7681-52-9, formula NaOCl. Buy it as 5 litres for around £18.00 from Amazon UK.
Working strength: 1:1 with water (yields ~7.5% working solution) + 10 ml washing-up liquid. Indicative cost £1.80 per diluted litre — 64% below a typical branded pack on a per-litre basis, before you reuse leftover bulk.
Follow the mixing method and the supplier SDS. Wear the listed PPE. Do not mix incompatible oxidisers, acids or ammonia.
- Apply onto completely dry paving using a chemical-resistant pump sprayer or plastic watering can.
- Allow 30–60 minutes dwell time without letting the surface dry out entirely.
- Rinse thoroughly with copious fresh water. Keep run-off away from delicate grass edges.
- Never mix with acids, vinegar or ammonia.
Dilution recipe
5 L sprayer
Working strength 1:1 with water (yields ~7.5% working solution) + 10 ml washing-up liquid. Educational estimate from the listed ratio — check the SDS before you mix.
Chemical
2,500 millilitres
Sodium hypochlorite 14–15% (industrial / dairy grade)
Water
2.5 litres
Carrier / diluent
50% concentrate · 50% water by working volume (solids are dissolved into the water share).
Required PPE
Loading calculator…
Side-by-Side Price & Potency Comparison
Head-to-head comparison
| Measure | Retail brandedHG | Raw active dupeDupeStack |
|---|---|---|
| Product | Hagesan Black Spot RemoverAmazon UK search — listing, not a confirmed seller | Sodium hypochlorite 14–15% (industrial / dairy grade) |
| Pack / unit | 5 litres · £24.99 | 5 litres · £18.00 |
| Active | Sodium hypochlorite at 9.5%Carrier: Water and surfactants | 15% bulkNaOCl |
| CAS number | Not disclosed on pack | 7681-52-9 |
| Working strength | Ready-to-use pack | Dilute 1:1 with water (yields ~7.5% working solution) + 10 ml washing-up liquid |
| Cost per litre | £5.00 / L typical pack | £1.80 / L mixed from bulk |
| Headline saving | Baseline | 64% cheaper |
| COSHH / PPE | Follow the branded SDS | Gloves. Chemical-resistant gloves (nitrile or neoprene)Eye protection. Indirect-vent splash goggles — not ordinary spectaclesRespirator. Rated respirator for dusts or vapours as specified on the SDSVentilation. Use outdoors or with mechanical extraction |
Active ingredient and cheaper alternative — FAQ
Is Hagesan Black Spot the same as Patio Magic?
No. Hagesan is sodium hypochlorite (bleach). Patio Magic is benzalkonium chloride (a quat). Different molecules, different risks. Never mix bleach with acids, ammonia or BAC.
What strength bleach matches the bottle?
Hagesan is around 9–10% hypochlorite. Thin 14–15% industrial/dairy bleach diluted 1:1 with water lands near 7–8% working liquor — scrub-and-rinse territory, not a walk-away quat. Keep run-off off grass edges.
How do you mix the Hagesan Black Spot Remover dupe stack?
Apply onto completely dry paving using a chemical-resistant pump sprayer or plastic watering can. Allow 30–60 minutes dwell time without letting the surface dry out entirely. Rinse thoroughly with copious fresh water. Keep run-off away from delicate grass edges. Never mix with acids, vinegar or ammonia.
DupeStack provides chemical concentration data and educational mixing guides only. Wellness pages compare food supplements, not medicines or prescribed treatments. Always review the supplier Safety Data Sheet (SDS) and comply with UK Health and Safety Executive (HSE) and COSHH regulations when handling concentrated substances. Mixing and storage are at your own risk. Some links are affiliate advertisements (Amazon Associates, eBay Partner Network, and Awin when those programmes are live). Commissions do not change listed concentrations or calculator output.
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Indicative DIY stack