Polishing pad colours don’t tell you the hardness

The question we get most before someone’s first machine polish sounds harmless enough: will this pad leave holograms on black paint? The honest answer doesn’t sit with the pad alone. It sits with the pairing of pad hardness and paint hardness, and nobody reads that off a colour. Red means heavy cut at one manufacturer and finishing at the next. Trust the colour code and sooner or later you take more clearcoat than the job ever needed.

A polishing pad carries the machine’s energy into the abrasive in the polish. The harder the pad, the more direct that path and the more clearcoat comes off. Which hardness is right is decided by the paint, not by the colour on the box.

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The pad decides the cut, not the polish

The same polish cuts several times deeper on a hard pad than it manages on a soft one. The pad is the carrier that presses the abrasive into the paint, and its compression hardness decides how much of that pressure actually arrives.

Physically it comes down to the energy budget. A hard polyurethane structure barely gives under pressure, so the rotation and oscillation of the machine reach the abrasive almost without loss. Soft foam springs instead: a good part of the kinetic energy disappears into the pad’s own compression before the abrasive even makes contact. That is why a soft pad smooths the surface rather than taking material off it.

How much material you have to work with is the second half of the sum. Total paint build on a production car runs 80 to 160 microns, and only 30 to 60 microns of that is clearcoat. That is the only layer you are allowed to polish. A single-stage finishing pass typically takes 1 to 3 microns, a two-stage correction of cut and finish adds up to 3 to 6 microns. Anything over 8 microns in one pass is wet-sanding territory and a warning sign in day-to-day work.

The reassuring part: keep every correction under 3 microns and a car takes five to ten machine polishes across its life. The uncomfortable part: reach for the hardest pad every single time and that budget is gone in a fraction of those years. We wrote the numbers out in full when we looked at how much clearcoat you really have when you polish scratches out.

Foam, wool and microfibre cut in that order

The three material classes do not differ by degree, they differ in kind. Wool cuts hardest, microfibre sits in between, and foam is the only real all-rounder on a dual action machine.

Foam is a polyurethane structure, and its cell structure dictates how it behaves. Open-cell, reticulated foams have no membranes left between the cells. They flex more, tear less easily and work like a pump under centrifugal force, pulling cool air in and carrying frictional heat out. Closed-cell foams hold the polish on the surface, give you more cut at the start, then saturate faster and trap heat. Manufacturers put numbers on hardness through compression hardness and cell density. ZviZZer quotes 18 kPa at 22 to 23 cells per centimetre for the hard version of its Thermo pads, and 4 kPa at 25 to 26 cells per centimetre for the ultra-soft finishing pad.

Wool works through fibres that reach into the troughs of a scratch like microscopic cutting tools. Classic twisted lambswool with fibres around 35 millimetres long belongs on a rotary. For a dual action there is short-pile hybrid wool with roughly 15 millimetre fibres woven into a damping foam base, and it finishes down with far fewer holograms. How big that gap is, SONAX prints straight on the box: the SONAX PROFILINE LammwollPad is rated Cut 5 and Gloss 3 on the company’s own six-point scale, while the SONAX PROFILINE SchaumPad hart comes in at Cut 4 and Gloss 5. More cut, less finish, in black and white.

Microfibre gives you both and pays for it in heat. Every single fibre carries abrasive, the contact area is enormous, and the friction rises to match. To stop the weave peeling off the hook-and-loop backing under that load, makers like Rupes inject liquid polyurethane resin straight between the backing plate and the fibre weave instead of gluing it. On hard paint, or paint that has been left alone for years, microfibre is the most efficient thing you can put on a dual action.

Red at Koch-Chemie is not red at ZviZZer

There is no DIN standard and no ISO standard for polishing foam. Every manufacturer assigns its own colours, and the systems contradict each other right across the market. This is exactly where the most expensive beginner mistake happens when you switch brands.

Manufacturer	Heavy cut	Medium	Finish
Koch-Chemie	Red	Yellow, orange	Purple, green
ZviZZer	Blue, red	Orange	Yellow, green
Rupes	Blue	Green, yellow	White
SONAX	Red	Green	Grey

Blue is the hardest pad ZviZZer makes and the coarsest cut at Rupes, while the same colour sits at the finishing end in other line-ups. Green is the softest pad at ZviZZer and Koch-Chemie, and the middle grade at SONAX. Move from one system into the other and take the colour as your signpost, and you can easily land two grades off.

Even inside a single brand, the data sheet beats the box. In one specification Koch-Chemie lists the Koch-Chemie Fine Cut Foam Pad "Gelb" (2024) at compression hardness 17 and abrasiveness 9 — and the same two figures turn up elsewhere for the noticeably more aggressive Koch-Chemie Heavy Cut Foam Pad "Rot" (2024). Contradictions like that in manufacturer paperwork are the real reason the test spot decides in the end, not the table.

The second figure most people skip is diameter relative to the backing plate. The SONAX PROFILINE SchaumPad hart measures 165 millimetres and is built for plates from 125 to 150 millimetres, the LammwollPad measures 133 millimetres for a 125 plate. That overhang is deliberate: the rim that stands proud cushions against edges and keeps the plate off the paint.

And pad size follows the machine, not the damage. On a 21 millimetre long-throw, big pads work most efficiently, because they cover the most ground per unit of time. On a 12 to 15 millimetre throw, 125 pads stay far more controllable, because the rotation stalls less often on edges and curves. On A-pillars, mirror caps and air intakes there is no way around 75 to 80 millimetres: a big pad bridges tight radii and only cuts on the raised edges, while the defects down in the hollows stay untouched.

The test spot comes before the whole car

The golden rule of paint correction is least aggressive first. You deliberately do not start with the hardest pad. You start with the mildest combination that could plausibly clear the defect, and you step up only when the result asks for it.

In practice it looks like this: tape off a patch of roughly 40 by 40 centimetres on a horizontal panel, so you get a hard visual edge against untouched paint. Then a medium pad with a medium polish, three to four cross-hatch passes at an arm speed of 2 to 3 centimetres per second, three to four pea-sized drops of polish on the pad. After that you wipe the panel down with isopropanol, no exceptions, because the gloss oils in a polish mask fine scratches. Only degreased paint under a strong inspection lamp shows you the honest result.

If the defect is still there, you step up exactly one parameter: the harder pad first with the same polish, then the more aggressive polish, and microfibre or wool in the extreme case. If the defect is gone and the paint looks hazy, the combination was too coarse for a finish and you add a second, soft pass. On pressure, a dual action wants a corridor of 6 to 8 kilograms for the cut, on a rotary the weight of the machine up to 3 kilograms is enough. A workable gauge without scales: the pad should compress by half at most, better by a third of its height.

What almost every guide leaves out is temperature. From 60 to 70 °C, clearcoat turns thermoplastic, sticks to the pad, saturates it and pays you back with holograms and haze. On painted plastic that matters more than on steel, because plastic traps the heat instead of carrying it away — the substrate can warp there and the paint film can lift. For scale: a black painted panel sits above 80 °C in full sun before a machine ever touches it.

On a day like today, 36 °C and a clear sky, that means one thing in practice: work early in the morning or work in the shade. Start a polish on a hot panel and the pad clogs on you within a few sections. And work the surface in sections of 40 by 40 up to 60 by 60 centimetres. Bigger patches dry on before you are finished with them.

Our polishing pads sorted by hardness

Our polishing pads category holds 67 items, and a good half of them are permanently in stock. Sorted by hardness, the range breaks down into four grades, and those four cover practically every level of defect.

For heavy cut there is the Koch-Chemie Heavy Cut Foam Pad "Rot" (2024) in Ø 45mm / 1.7", Ø 76mm / 3", Ø 126mm / 5" and Ø 150mm / 6". In verified Trusted Shops reviews, buyers describe it as a very hard pad for coarse polishes that takes deep scratches out reliably and keeps going. The SONAX PROFILINE SchaumPad hart sits at the same grade in Ø75 mm and Ø150 mm, with the manufacturer’s own Cut rating of 4 at Gloss 5 — noticeably kinder to the finish than straight wool.

The middle grade is the Koch-Chemie Fine Cut Foam Pad "Gelb" (2024), which users file as a medium pad that clears light scratches and already leaves a clean finish behind it. For the finish itself you reach for the Koch-Chemie Micro Cut Soft Foam Pad "Violett" (Weich) (2024), named in the reviews for exactly the job that keeps coming up in customer questions: pulling holograms out reliably and bringing deep gloss back. Top of the aggression scale is the SONAX PROFILINE LammwollPad, which belongs on a rotary and needs a finishing pass after it, no exceptions.

Across all the pads in our range there are 25 verified Trusted Shops reviews at an average of 4.9. If you are starting out, you do not buy one pad per colour, you buy three to six of the same type. The reason is in the next section, and it has more to do with pad life than with convenience. Matching machines and polishes are in our Polishing category.

German clearcoat needs a hard pad, Japanese does not forgive one

If you take one thing away from this piece, take this: pad choice starts with the paint, not with the defect. One and the same scratch calls for a different pad on a Mercedes than it does on a Mazda.

German premium manufacturers run very hard clearcoats, some of them ceramically cross-linked. On the pencil hardness scale, regular automotive clearcoats sit around 2H, and highly cross-linked polyurethane systems reach 3H. Come at that with a soft finishing pad and a cutting polish and nothing happens at all, because the energy disappears into the compression of the foam. Japanese paint from Honda, Toyota, Subaru or Mazda behaves the other way round: it is soft and it reacts badly to hard, reticulated foam, because the polyurethane structure is abrasive in its own right and drags micro-marring into the surface. American paint spreads across the whole range, from very hard on a Corvette to soft on a Dodge.

One exception that gets missed surprisingly often is resprayed panels. Factory clearcoat bakes at around 140 °C and cross-links to the maximum. A repair respray cures on the assembled car at around 60 °C and stays noticeably softer. So a resprayed door often needs a different pad than the wing next to it. When your paint depth gauge suddenly reads over 150 microns on one panel, that is your clue. If it drops under 90 microns, the heavy cut pads and the wool go away before you risk burning through.

That answers the one-step question customers put to us regularly. If the paint is hard and the defect is moderate, a medium pad with a one-step polish is the right call. If the paint is soft, you pick one grade below that, because otherwise you create exactly the holograms you set out to remove.

And when the defect is deep, there is no one-step. The heavy cut has to be followed by a soft finishing pass, otherwise the haze from the first run stays in the paint. Which defects fall into which category is easiest to see in raking light. How that works is in our piece on spotting swirls in your paint.

Detailing1 insight: Questions like this land with us regularly: there is a fine crack in the pad that arrived, is that normal? No, a crack from the factory is a material fault and it goes back. The more interesting case is the crack after a few cars, and that one is almost always self-inflicted. Drag one single pad across a whole car and you hold it above 60 °C the entire time, the foam collapses and the cell walls tear. Pads treated that way are done after two to five cars. Rotate three to six pads of the same type and brush them out after every section, and the same pad lasts eight to over twenty cars. The retirement test takes two seconds: squeeze it, let go. If it does not come back into shape it is finished, however clean it looks.