Acid Car Shampoos Compared: Purìfica, Koch RS, Yum Reset and Renova

By Paolo Recinella, BSc, DipEd · trains and accredits Labocosmetica and Feynlab coating applicators · Alpha Details, Heidelberg West, Melbourne

If your coated car has stopped beading and a neutral wash doesn't bring it back, the coating is probably fine. It is buried. Hard water, sprinklers and dusty rain leave a thin mineral film on top of the protection, and that film is what stops the water running off. Neutral and alkaline washes cannot dissolve minerals. An acid shampoo can.

We stock four acid shampoos and an acidic presoak for rinseless washing. They are not interchangeable: they differ in strength, in what their makers certify them for, and in what they cost per bucket. Every figure below is the manufacturer's own. Where a maker does not publish a number, we say so rather than guess.

Purìfica: VDA-certified acid shampoo and foam.

Koch Chemie RS: pH 3.0 at 1:200.

Yum Reset: shampoo, water softener and mineral remover.

What an acid shampoo actually removes

Water spots and limescale are mostly calcium and magnesium carbonate, left behind when hard water evaporates. They are ionic, mineral deposits: surfactants slide over them and alkaline chemistry leaves them untouched. An acid reacts with the carbonate and turns it into a soluble salt that rinses away. Most acid shampoos also carry a chelating agent, which grabs the freed calcium and keeps it in solution so it cannot redeposit as the panel dries.

The pH tells you which job a product can do, not how hard it is on your car. Every pH step is a factor of ten, so pH 3 has 100 times the hydrogen-ion activity of pH 5, but the acid used, the buffering, the dwell time and the surface decide what that means in practice. That is the argument in our pH guide. For an acid shampoo, the practical point is simpler: the same bottle sits at a different pH depending on how much you put in the bucket, so a pH figure only means something next to its dilution.

The five we stock, on the makers' numbers

Labocosmetica Purìfica

Labocosmetica built Purìfica to remove the thin, often invisible limescale film it blames for lost shine, particularly on dark cars, and to bring a nano-coating or sealant back to life. It is VDA-certified, and Labocosmetica lists aluminium, plastic, paint, glass and PPF among its materials, with a "safe for protections" claim: it does not damage existing protection and contains no wax or sealant of its own. It has the most detailed instructions of any product here: 1:5 to 1:10 in a foam gun, 1:100 to 1:400 in a bucket, 1:100 to 1:200 in an atomiser, 1:30 for stubborn limescale or wheels, and 1:400 as a routine coating-maintenance wash. Labocosmetica's ingredient sheet lists methanesulphonic and sulphamic acid with a GLDA chelator.

Koch Chemie RS Reactivation Shampoo

Koch call RS an acidic descaling soap that reactivates ceramic coatings, removing dust, limescale and salts so the coating's water-repellency comes back. Their instructions are short and specific: alkaline pre-clean and pressure rinse first, then a hand wash at 1:200, which Koch state gives pH 3.0. For a foam cannon they say only to adjust the pre-dilution, without a ratio. Koch list paint, glass and exterior plastics, ask you to check material compatibility first, and say not to let it dry.

Yum Reset

Yum Cars describe Reset as a 3-in-1: a mild strip shampoo, a water softener and a mineral remover. They say it removes water spots, limescale and traffic film, unclogs ceramic coatings, prepares paint for polishing, and removes waxes and sealants nearing the end of their lifespan. They also describe it for weekly maintenance of protective layers. Yum give wash-solution pH by dose rather than ratio, measured in average UK water: 150 ml gives pH 4, 100 ml pH 5.5 and 50 ml pH 6.0, and they say to adjust for local water. Melbourne water is soft, so expect to need less. We read the dose as the control: a low dose for a maintenance wash, the full dose when you want the reset.

Labocosmetica Renova

Renova is the specialist. Labocosmetica designed it for traffic film, minerals and carbon embedded in the structure of paint protection film and wraps, and certify it VDA for thermo-sensitive surfaces. Labocosmetica's own distinction is useful: Purìfica renews the appearance; Renova works inside the film. Use it at 1:50 as a hand wash (20 ml per litre), 1:200 as a PPF maintenance shampoo, or 1:10 as a spot treatment left a maximum of 60 seconds. It pairs with Lìbera, alkaline first, in Labocosmetica's 2pH+ cycle. Our film routine is in how to care for paint protection film.

Labocosmetica Prelùdio Acidic

For rinseless and waterless washers. Prelùdio Acidic is sprayed on before the rinseless wash to dissolve limescale and sandy-rain residue: 1:5 on wheels and obvious limescale, 1:10 after sandy rain, 1:50 for coating maintenance. Labocosmetica give about a minute's dwell, and call it gentler than a dedicated limescale remover, so it can be used often.

What a bucket costs

For a 10-litre bucket, using each maker's routine dilution and our current prices:

Which one should you buy?

Safety, from the data sheets

Acid concentrates deserve respect even when the diluted wash is mild. Koch's safety data sheet for RS classifies the concentrate as Danger: it causes severe skin burns and eye damage and may be corrosive to metals, so keep the neat product off bare aluminium. Purìfica's label carries skin and eye damage warnings. Labocosmetica and Yum do not publish safety data sheets for Renova, Prelùdio Acidic or Reset on their sites. Whatever you use, wear gloves and eye protection when you dilute, and none of these makers publish a hot-panel rule, so here is ours: cool panels, in the shade, rinse before anything dries.