Start with the job, not the brand
Patio bottles sell a story: walk away, no scrubbing, organic, trade-strength. The SDS usually names one active. Match the active to the stain before you buy a jerry can.
Green slime and algae film → quaternary ammonium (BAC or DDAC). Organic film you can scrub → sodium percarbonate oxygen bleach (Logco-style patio powder). Black lichen dots on sandstone → often hypochlorite. Cement haze → dilute hydrochloric on acid-safe stone. Oil and traffic grime → alkaline degreaser (metasilicate or TKPP). Deep motor-oil spots in stone → solvent / citrus poultice (Lithofin OIL-EX), then an alkaline wash. Old wax or acrylic sealer → benzyl alcohol stripper, then reseal.
BAC vs DDAC
Wet & Forget and Patio Magic are benzalkonium chloride (CAS 68424-85-1). Jeyes 4-in-1 Patio Power is didecyldimethylammonium chloride (DDAC, CAS 7173-51-5). Both are quats used on algae; they are not interchangeable on the label, and neither should be mixed with bleach, acids or washing-up liquid.
If two brands share a CAS, pick the teardown whose dilution matches the job and the pack you can actually buy. Classic ‘tar acid’ Jeyes Fluid is gone — do not hunt chlorocresol for a modern patio bottle.
Bleach, acid, degreaser, stripper
Hypochlorite (Hagesan-style) oxidises organic stains; rinse plants and keep pets off until dry. Sodium percarbonate (Logco Eco patio powder, CAS 15630-89-4) is a different oxidiser — dissolve 50 g/L, scrub and rinse; it is not a walk-away quat and not bottle bleach. Brick acid is a different tool — mineral, not biological. Metasilicate (KilrockPRO) and TKPP (LTP Grimex) lift grease; a hydrocarbon / d-limonene poultice (OIL-EX) pulls deep oil; Solvex-style benzyl alcohol softens sealers so you can scrub them off. Thompson’s Water Seal is one reseal: a water-based n-octyltriethoxysilane (CAS 2943-75-1), dilute 50% concentrate 1+9. Lithofin Stainstop PLUS is a different reseal — solvent-borne amino-functional dimethyl siloxane (CAS 69430-37-1) at about 15–20%, used neat, and it darkens absorbent stone. Do not treat the two tins as the same impregnator.
Never stack quat + bleach, acid + bleach, oxygen powder + hypochlorite, or acid + alkaline degreaser in one bucket. One chemistry per wash; rinse between if you change tack.
Measure the patio first
Guessing litres is how people overspend on branded concentrate. Measure length × width, then use the area estimator or open the calculator in area mode against a teardown.
FAQ
- Is Patio Magic the same as Wet & Forget?
- Same molecule family: both are benzalkonium chloride (BAC) patio biocides. Strengths differ on the label; the DIY stack is the same drum of BAC 50 with different dilution maths.
- Will BAC remove black spot lichen on sandstone?
- BAC is strong on green algae and soft film. Deep black lichen dots are often a hypochlorite job. Do not mix quat biocides with bleach.
- When do I need brick acid instead of a patio spray?
- Hydrochloric acid (Mortar Clen-style) is for cement smears and mineral scale on acid-safe masonry — not for algae film. Test first; never on limestone or marble.
More patio & exterior guides
Patio guide
How much patio chemical do you need? Measure first
Patio guide
BAC vs DDAC vs bleach on patios — which active for which stain?
Patio guide
When to use a metasilicate degreaser on driveways
Patio guide
Driveway oil stains: degreaser vs solvent vs absorbent
Patio guide
Water-repellent, biocide or acid — which patio job needs which chemistry
Patio guide
Driveway & TFR oil and grease: which solvent for which stain
Related teardowns
Live stacks this guide points at — mix maths and DIY affiliate links on each page.
Patio & exterior
Wet & Forget Exterior Surface Cleaner
Wet & Forget
- Retail pack
- £34.005 litres
- Raw active
- Benzalkonium chloride (BAC 50)68424-85-1
A dilute quaternary ammonium biocide sold as a lifestyle patio product. The active is commodity BAC 50; the brand is paying for the trigger bottle and the television advert.
Patio & exterior
Patio Magic!
Patio Magic
- Retail pack
- £24.995 litres
- Raw active
- Benzalkonium chloride (BAC 50)68424-85-1
Another BAC patio biocide in a different coloured bottle. Same quaternary ammonium as Wet & Forget; same bulk drum of BAC 50. You are paying for the brand, not a different molecule.
Patio & exterior
4-in-1 Patio Power
Jeyes
- Retail pack
- £16.004 litres
- Raw active
- Didecyldimethylammonium chloride (DDAC 50)7173-51-5
This is not old Jeyes Fluid (tar acids are gone). Patio Power is 1.75% DDAC — a twin-chain quat, not the benzalkonium in Patio Magic. Dilute DDAC 50 to about 0.35% and you have the same working spray as the 4 L bottle mixed 1+4.
Patio & exterior
Hagesan Black Spot Remover
HG
- Retail pack
- £24.995 litres
- Raw active
- Sodium hypochlorite 14–15% (industrial / dairy grade)7681-52-9
Standard commercial bleach solution sold at five times agricultural merchant prices.
Patio & exterior
Mortar Clen Brick & Patio Acid
Everbuild
- Retail pack
- £16.505 litres
- Raw active
- Technical hydrochloric acid 32–36%7647-01-0
Retail brick acid is technical hydrochloric acid cut to about 9%. 5 litres of 36% acid plus 15 litres of water is 20 litres of the same working strength.
Patio & exterior
Organic Path, Patio & Deck Cleaner Concentrate
Algon
- Retail pack
- £11.992.5 litres
- Raw active
- Spirit vinegar 25% (acetic acid)64-19-7
The ‘organic patio cleaner’ is about 18% acetic acid with a drop of sugar-derived surfactant. Dilute 1:3 and you have ~4.5% vinegar. Spirit vinegar at 25% is the same molecule in a 5 litre jerry.
Patio & exterior
Patio, Driveway & Masonry Cleaner
KilrockPRO
- Retail pack
- £14.005 litres
- Raw active
- Sodium metasilicate pentahydrate10213-79-3
This is not Patio Magic (BAC) and it is not Mortar Clen (HCl). KilrockPRO is a dilute alkaline masonry degreaser — disodium metasilicate (CAS 6834-92-0) with soda ash and a chelator. Metasilicate pentahydrate crystals mixed at about 30 g/L match the bottle strength; then dilute 1:20 for light stains as the pack does.
Patio & exterior
Grimex Intensive Cleaner
LTP
- Retail pack
- £33.005 litres
- Raw active
- Tetrapotassium pyrophosphate (TKPP)7320-34-5
Not a patio biocide (BAC/DDAC) and not brick acid. LTP’s 2025 SDS lists tetrapotassium pyrophosphate (~1–3%) with glycol ether and a little ammonia — a phosphate-builder scrub for grease and old wax. TKPP crystals at about 20 g/L match the bottle’s builder strength; then dilute as the pack does.
Patio & exterior
Solvex High Performance Remover
LTP
- Retail pack
- £18.001 litre
- Raw active
- Benzyl alcohol100-51-6
A viscous sealer stripper whose SDS lists benzyl alcohol at roughly 30–50%. Bulk benzyl alcohol is the same solvent that softens wax and acrylic films so you can scrub and wet-vac them off — not a biocide and not brick acid.
Patio & exterior
Water Seal Masonry Protector
Thompson's
- Retail pack
- £36.005 litres
- Raw active
- Water-based silane/siloxane masonry impregnator (50%)2943-75-1
A dilute siloxane in a 5 litre tin. Trade water-based silane/siloxane concentrates at 50% dilute 1+9 to about 5% working sealer — same job, more litres, less solvent perfume.
Patio & exterior
Stainstop PLUS
Lithofin
- Retail pack
- £43.801 litre
- Raw active
- Lithofin Stainstop PLUS (same siloxane impregnator, 5 litre tin)69430-37-1
Not Thompson’s water-based silane. The GB SDS for Lithofin Stainstop PLUS lists an amino-functional dimethyl siloxane (CAS 69430-37-1) at 15–20% in hydrocarbon solvent, plus a trace of methanol. It sinks in and darkens absorbent stone. Pro Tiler Tools lists the same tin at £43.80 for 1 litre and £202.20 for 5 litres (inc VAT) — about £40 a litre in the big tin, an 8% tin-size gap, not a stronger molecule.
Patio & exterior
Eco Patio & Decking Cleaner
Logco
- Retail pack
- £29.995 kg tub
- Raw active
- Sodium percarbonate (technical oxygen bleach)15630-89-4
Logco’s Eco patio powder is sodium percarbonate (CAS 15630-89-4) — the same solid peroxide adduct as Vanish Oxi, sold as a 5 kg outdoor tub. Fifty grams per litre of warm water is the deck/patio band (about 5 m²/L). It is not BAC, not DDAC and not hypochlorite. A technical 5 kg sack is the same oxidiser without the decking label.
Patio & exterior
OIL-EX Oil Stain Remover
Lithofin
- Retail pack
- £16.56250 millilitres
- Raw active
- Low-aromatic C9–C10 white spirit plus fuller’s earth poultice64742-49-0
Lithofin OIL-EX is a solvent poultice, not an alkaline degreaser. The GB SDS lists C9–C10 hydrocarbons (CAS 64742-49-0) at 60–65%, C9 aromatics (CAS 64742-95-6) at 15–20%, and d-limonene (CAS 5989-27-5) at 0.5–1% in an absorbent paste. It is not KilrockPRO metasilicate, not LTP Grimex TKPP, and not Solvex benzyl alcohol. Low-aromatic white spirit plus fuller’s earth is the same solvent-and-absorb job without the 250 ml tube tax.
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