Household cleaning
Viakal Classic Limescale Remover Spray dupe
Why pay around £3.00 for Viakal? The bulk active is Formic acid 85% (diluted to ~3%) — 85% less per working litre than a typical shelf pack.
From the retail pack to the active and the mix
1 · Retail
Viakal Classic Limescale Remover Spray
500 millilitres · £3.00 typical snapshot
Water, alcohol ethoxylate and perfume
2 · Active
Formic acid (with citric acid)
3% on the label
64-18-6HCOOH
Bulk Formic acid 85% (diluted to ~3%)
3 · Mix
1:27 (1 part 85% + 27 parts water → ~3%)
£0.45 per working litre · 85% less than the shelf pack
- Active
- Formic acid (with citric acid)
- CAS
- 64-18-6
- Dupe
- Formic acid 85% (diluted to ~3%)
- Saving
- 85% / 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
“Removes limescale, soap scum and watermarks”
The chemical reality
Current UK Viakal Classic spray is formic acid (CAS 64-18-6) at about 1–5% plus citric at 1–5% — not Fernox sulfamic crystals and not Cillit Bang’s citric/sulfamic kitchen trigger. Dilute 85% formic 1:27 to the same ~3% band. Older professional Viakal listed sulfamic or maleic — read the SDS on the bottle you hold.
Active vs filler
3% Formic acid (with citric acid) · 97% carrier / filler — Water, alcohol ethoxylate and perfume
- Typical retail
- £3.00
- 500 millilitres
- Estimated active cost
- £0.22
- Scaled from bulk £12.50 / 1 litre
- Indicative markup
- 13.6×
- Snapshot maths, not a live shop price
The Marketing Claim & The Catch
A 500 millilitres pack of Viakal Classic Limescale Remover Spray typically retails around £3.00 in household cleaning. 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: Removes limescale, soap scum and watermarks; Anti-droplet technology to slow scale return; and Everyday bathroom spray for taps and showers.
The catch: Current UK Viakal Classic spray is formic acid (CAS 64-18-6) at about 1–5% plus citric at 1–5% — not Fernox sulfamic crystals and not Cillit Bang’s citric/sulfamic kitchen trigger. Dilute 85% formic 1:27 to the same ~3% band. Older professional Viakal listed sulfamic or maleic — read the SDS on the bottle you hold.
- “Removes limescale, soap scum and watermarks”
- “Anti-droplet technology to slow scale return”
- “Everyday bathroom spray for taps and showers”
Proprietary Blend & Dosage Breakdown
The labelled active is Formic acid (with citric acid) at 3%. Everything else in the pack is water, alcohol ethoxylate and perfume.
At 3% 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 85% Formic acid 85% (diluted to ~3%), mixed to 1:27 (1 part 85% + 27 parts water → ~3%).
- Labelled active
- Formic acid (with citric acid)
- 3%
- Carrier
- Water, alcohol ethoxylate and perfume
- Retail pack
- 500 millilitres · £3.00
The Active Chemical Alternative (Dupe Stack)
The dupe stack is Formic acid 85% (diluted to ~3%) at 85% bulk. Indexed as CAS 64-18-6, formula HCOOH. Buy it as 1 litre for around £12.50 from Amazon UK.
Working strength: 1:27 (1 part 85% + 27 parts water → ~3%). Indicative cost £0.45 per diluted litre — 85% 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.
- Corrosive concentrate. Splash goggles, household gloves, ventilation. Always add acid to water. Formic vapour is sharp — do not breathe the neat jerry. Never mix with bleach.
- Pour 35 ml of 85% formic acid into 965 ml of cold water in a labelled trigger bottle (1:27). That lands near 3% — the Viakal Classic spray band. Optional: 10 g of food-grade citric in the same litre if you want the dual-acid SDS.
- Spray onto wet taps, tiles and shower screens. Dwell a minute, wipe, rinse. Keep off marble, limestone, gold-plated fittings and stone you care about.
- 1 litre of 85% at 1:27 makes about 28 litres of 3% spray — more than fifty 500 ml Viakal bottles.
- Store the jerry locked and labelled. This is a bathroom descale, not a kettle sachet (citric or sulfamic) and not brick acid.
Dilution recipe
0.5 L working batch
Working strength 1:27 (1 part 85% + 27 parts water → ~3%). Educational estimate from the listed ratio — check the SDS before you mix.
Chemical
18 millilitres
Formic acid 85% (diluted to ~3%)
Water
0.48 litres
Carrier / diluent
4% concentrate · 96% 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 brandedViakal | Raw active dupeDupeStack |
|---|---|---|
| Product | Classic Limescale Remover SprayAmazon UK search — listing, not a confirmed seller | Formic acid 85% (diluted to ~3%) |
| Pack / unit | 500 millilitres · £3.00 | 1 litre · £12.50 |
| Active | Formic acid (with citric acid) at 3%Carrier: Water, alcohol ethoxylate and perfume | 85% bulkHCOOH |
| CAS number | Not disclosed on pack | 64-18-6 |
| Working strength | Ready-to-use pack | Dilute 1:27 (1 part 85% + 27 parts water → ~3%) |
| Cost per litre | £6.00 / L typical pack | £0.45 / L mixed from bulk |
| Headline saving | Baseline | 85% cheaper |
| COSHH / PPE | Follow the branded SDS | Gloves. Chemical-resistant gloves (nitrile or neoprene)Eye protection. Indirect-vent splash goggles — not ordinary spectaclesVentilation. Use outdoors or with mechanical extractionAcid-resistant PPE. Apron and gloves rated for corrosive liquids |
Active ingredient and cheaper alternative — FAQ
Is Viakal the same as Cillit Bang limescale spray?
Same job (bathroom scale) but different acids on current UK SDS sheets. Viakal Classic spray is formic acid plus a little citric. Cillit Bang is typically citric and/or sulfamic. HG Super Powerful foam is phosphoric. Pick the teardown that matches the bottle.
Is this the same as Fernox DS-3?
No. Fernox DS-3 is solid sulfamic acid for kettles and heating circuits. Viakal Classic spray is a dilute formic bathroom trigger. Do not pour 85% formic into a combi loop, and do not treat Fernox crystals as a tap spray without diluting.
How do you mix the Classic Limescale Remover Spray dupe stack?
Corrosive concentrate. Splash goggles, household gloves, ventilation. Always add acid to water. Formic vapour is sharp — do not breathe the neat jerry. Never mix with bleach. Pour 35 ml of 85% formic acid into 965 ml of cold water in a labelled trigger bottle (1:27). That lands near 3% — the Viakal Classic spray band. Optional: 10 g of food-grade citric in the same litre if you want the dual-acid SDS. Spray onto wet taps, tiles and shower screens. Dwell a minute, wipe, rinse. Keep off marble, limestone, gold-plated fittings and stone you care about. 1 litre of 85% at 1:27 makes about 28 litres of 3% spray — more than fifty 500 ml Viakal bottles. Store the jerry locked and labelled. This is a bathroom descale, not a kettle sachet (citric or sulfamic) and not brick acid.
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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£22.50Save 85% / L
Indicative DIY stack