Wet vs Dry polishing, which is better?

We get asked this daily, and the honest answer is that there is no single winner. In most situations there is a crossover where wet and dry polishing are equally effective, and the right choice comes down to the material, the setting and how much you intend to do. The most useful way to decide is to understand what each product is designed for, so this guide walks through wet diamond pads, dry diamond pads and silicon carbide pads, then the machines, so you can match the method to your set-up.

Wet diamond pads

These are usually Velcro-backed pads with diamond suspended in resin, sometimes a resin and copper mix. Running water with them keeps the resin cool, stops the pad overheating and burning out too quickly, and flushes the cut waste away as a slurry. As with all polishing pads, the lower the number the coarser the pad.

Wet polishing consistently produces the best finish when you are chasing a true mirror shine. The pads are less expensive than the dry variants, but the machinery to run them is generally dearer, and it is messy work; you will want wellies and a full-length apron to stand any chance of staying dry. The pay-off is versatility and finish quality. Wet diamond pads will polish almost anything, from porcelain, marble, terrazzo, quartz, limestone and travertine right up to the hardest granite. In every tile, stone and quartz factory in the world there are line-polishing machines running diamond pads cooled by water to finish the product. A graded set of premium wet diamond polishing pads covers the full sequence from coarse to high shine.

Dry diamond pads

Dry pads are also Velcro-backed, with diamond suspended in resin, but the resin is denser and harder so it can withstand higher temperatures. They work in the same way as wet pads, wearing away the resin to expose the diamond that does the polishing, and again the lower the number the coarser the pad.

The obvious advantage is that you do not have to dress like a fishmonger to use them, and they can be used where wet pads are simply impractical, such as on a finished, fitted job or for smaller jobs where setting up a full wet rig would take too long. The trade-off is dust. If you are polishing in volume, dust extraction becomes important, as does protecting the air you breathe with the right mask. The technology has moved on to the point where a good dry pad finishes very nearly as well as a wet one, so there is little to choose on surface quality. Dry pads cost more to buy than wet pads, and because the harder resin suits higher temperatures they are particularly at home on harder materials such as granite and dense concrete. You can polish softer sedimentary and metamorphic stone such as limestone, travertine and marble with dry pads too, but they often need dressing before first use, which means running them in on something very dense, like black granite, to expose some diamond. A set of super premium dry diamond polishing pads is the convenient choice for on-site finishing.

A word on dust and health

Dust filtering matters most with man-made products such as engineered stone and quartz, where there is concern that the dust produced when polishing could be harmful. Whatever the final verdict, the sensible approach is to play safe: use dust extraction and appropriate respiratory protection when dry polishing these materials, or polish them wet to suppress the dust at source.

Silicon carbide pads

Silicon carbide (SiC) pads, also known as carborundum, are a fine grit glued to the face of paper or cloth discs. As with sandpaper, the grit size sets the coarseness. They come paper-backed or velour-backed. The paper-backed discs are cheaper but need a plain backer and some contact adhesive to stick them down; most masons use a carpet or vinyl contact adhesive available from flooring stores. The velour-backed SiC discs attach to a Velcro backer, so you skip the sticking and unsticking, which you pay a little more for. The cheaper plain-backed SiC discs are the economy option where you are happy to use adhesive.

These pads have a short lifespan but are inexpensive, so they are treated as throwaway items like sandpaper. The velour-backed pads are used dry only. The plain-backed pads are used dry up to P320 grit, and above that can be used wet, from P400 through to P1200. SiC pads will polish marble, travertine, limestone, porcelain, quartz, fibreglass, plastics and glass, which makes them extremely versatile, and you will find boxes of them in every stonemason’s yard. The main reason to step up to diamond pads is economy when your SiC consumption is high, or convenience, since one set of diamond pads will outlast several boxes of SiC.

Wet, dry or SiC at a glance

The machines

There is a wide choice of machines for polishing, and the key is to match the machine to how you intend to work rather than to buy on price alone. The two things that matter most are whether you need water feed and what speed range you require. A dedicated wet polisher with a centre water feed sends water down the spindle and through the hole in the centre of wet pads, which is the cleanest way to keep them cool and is ideal for volume wet work. A variable-speed machine gives more flexibility, letting you run profiling and grinding as well as polishing, and lets you set a lower speed for delicate work. For a dedicated water-fed option, see the Eibenstock water-fed polisher, and the wider power tools range covers wet and dry machines.

One practical point with any variable-speed machine, whatever the brand: they do not cope well with extended use at the very low end of their speed range, where they tend to overheat. By extended we mean 30 minutes or more of continuous running. So think about how you will actually use the machine before buying, and choose one that will spend most of its time running closer to its top speed if your work is heavy.

So, which is better?

For the finest finish and the lowest pad cost on high-volume work, wet wins, provided you can live with the mess and the more expensive machine. For finished, fitted jobs, smaller tasks and hard materials, dry is more practical and now finishes nearly as well. Silicon carbide is the budget, versatile choice for mixed, lower-volume work. Many masons keep all three to hand and pick whichever suits the job in front of them.

Common mistakes

• Running wet pads with too little water. Skimping on water overheats and burns out the pad.
• Using dry pads on soft stone without dressing them first. They need running in on something dense to expose the diamond.
• Polishing engineered stone dry without extraction. Control the dust at source or polish wet.
• Skipping grits. Whatever the pad type, work through the sequence in order for an even finish.
• Holding a variable-speed machine at the bottom of its range for long runs. It will overheat; pick a machine suited to your speed needs.

FAQ

Is wet or dry polishing better for a mirror finish?

Wet polishing consistently produces the best mirror shine, which is why stone and quartz factories use water-cooled diamond pads on their line-polishing machines. That said, modern dry pads now finish very nearly as well, so for many jobs there is little to choose on surface quality and the decision comes down to mess, setting and material.

When should I use dry diamond pads instead of wet?

Use dry pads where wet pads are impractical, such as on a finished, fitted job where you cannot have water about, or on smaller jobs where setting up a full wet rig would take too long. Dry pads also suit hard materials like granite and dense concrete. Just plan for the dust with extraction and a suitable mask.

Are silicon carbide pads as good as diamond pads?

Silicon carbide pads are versatile and cheap and will polish a wide range of materials, but they wear out quickly and are treated as throwaway items like sandpaper. Diamond pads cost more up front but one set outlasts several boxes of SiC, so the reason to switch to diamond is usually economy at higher volumes, or the convenience of fewer pad changes.

Do I need water feed on my polishing machine?

You need water feed if you are running wet pads in any volume, as a dedicated wet polisher sends water down the centre spindle to keep the pads cool cleanly. For dry polishing you do not, but you should fit dust extraction instead. A variable-speed machine offers the most flexibility if you want to do more than one type of work.

Is the dust from polishing quartz dangerous?

There is concern that dust from polishing man-made products such as engineered stone and quartz could be harmful, so the sensible approach is to play safe. Either polish these materials wet to suppress the dust at source, or, if polishing dry, use dust extraction and appropriate respiratory protection.

Can I use the same machine for wet and dry polishing?

Some variable-speed machines can be used both ways, and you will occasionally see a dry polisher used with a hose trickling across the work. If you intend to do that, choose the 110v version for safety around water. Bear in mind that variable-speed machines overheat if held at the very bottom of their speed range for long continuous runs, so pick a machine suited to how you will actually work.