Last Updated on August 28, 2022 by Barry Gray
Polishing concrete with an orbital sander is a difficult task, especially when taking on large projects such as concrete floors, but it is possible and sometimes the only option available.
Polishing Concrete with an orbital sander is not ideal, and there are more effective options available to choose from. It is far from impossible, however, and with some effort and using the correct tools, you can achieve a smooth polished concrete surface.
Before deciding to sand and polish a concrete floor or countertop using an orbital sander, it is essential to understand which equipment and methodology are needed using this method.
How To Polish Concrete With An Orbital Sander?
When considering using an orbital sander to polish Concrete, the “how” becomes at least as critically important as the “which.”
Although messy and requiring a good amount of elbow grease to get the desired result, “wet” sanding is an absolute must. This is not a job that should be done using only the dry method.
Dry sanding tends to burnish the Concrete instead of polishing. Sandpaper is designed for use with wood or metal, not Concrete. The grit and grain required for concrete sanding are harder, requiring more abrasive properties than other sanding applications.
The dust and fine gritty particles will get trapped under the sanding pad and clog up the orbital sander. Ensure you have an adequate dust extraction system mounted, or simultaneously use a vacuum cleaner with a suction pipe to remove dust during the entire process.
Depending on the hardness and age of the Concrete, start with a 50 or 100 grit silicon carbide wet and dry sandpaper. Gradually work your way up to 2000 or 3000 grit. The standard wood or metal sandpaper contains particles that are not hard enough, which will not work.
If you’ve dry sanded your Concrete first, and it has exposed some sandy grains or decorative aggregate glass or stone, then you will need to tackle the much harder aggregate with something more aggressive and brutal than sandpaper.
The best way to do this is using a wet diamond polishing disc (100 grit or 200 grit) and a regular random orbit sander. Spray some water on the concrete surface to wet it liberally, and “sand” the surface using the diamond disc to rasp away the burnished surface. Take your time, as random orbit sanders are not nearly as aggressive as wet polishers.
In the polishing phase, one approach is to apply a chemical hardener to the Concrete after the rough sanding. This helps to make the Concrete denser and can assist in facilitating a more highly polished result.
Generally, the higher the grit count, the more polishing is achieved (rather than sanding or smoothing).
Bear in mind that a very highly polished surface will struggle to absorb any sealer if you hope to seal the Concrete afterward. Therefore, it is a bit of a give and takes, depending on what you hope to achieve.
After finishing the sanding phase, apply a few coats of acid wash to remove any remaining sandpaper scratches.
Orbital vs. Random Orbital Polisher
Establishing the fact that although not ideal, yet possible to use an orbital sander to polish your Concrete, the next factor to consider is the type and uses of different orbital sanders. Not all orbital sanders are considered appropriate for every kind of concrete sanding or polishing application.
There are significant differences in the characteristics when comparing orbital and random orbital sanders or polishers.
A standard orbital sander has a square or rectangular sanding shape and area and moves in a small circular motion around a small orbit. It could leave swirl patterns in the finish of the object being sander, even though a roughly finished concrete object, especially something like a concrete floor, should not typically show too much evidence of this.
An advantage of a standard orbital sander is that it can easily access hard-to-reach edges and corners thanks to its square base. It also uses sanding sheets, which are cut to size and clipped into place on the sander.
Random Orbital Sander
As the name suggests, random orbital sanders move back and forth in an oscillation spin and appear to make a random pattern. This movement pattern does not leave as many distinct marks as is the case with its standard counterpart, which might be preferable in fine applications such as tables and countertops.
The random orbital sander uses Velcro type sanding disks which are fast and easy to fasten and replace. These sanding disks do tend to be more expensive than the standard variety.
The Right Tool For The Right Job
When sanding a concrete surface, it’s important to know what the desired result should look like. Remember that an unfinished concrete surface is typically quite rough and hard, making it a difficult substrate to work with when using inadequate tools.
Polishing any surface implies that a silky smooth, glossy look and feel is desired. This surface could include a concrete floor, as often seen in a garage, a countertop in a kitchen or workshop, or even a concrete top table.
A properly polished concrete surface can only be accomplished using a fine-grit sanding disk or pad and a vibrating, abrasive hand tool powerful enough to achieve this result.
If you don’t have a sander or polisher on hand and need to rent one, then inquire at your local tool-hire whether they stock a walk-behind polisher, which is the most effective option for this job, especially when it’s a concrete floor that needs polishing.
Alternatively, if you find yourself needing to purchase one, go for a mid-range yet adequately powerful orbital or random-orbital option. Stay away from the cheap and nasty brands that will usually not have the requisite power to get the job done or fall apart halfway through the project.
Look out for a good deal online and check the reviews or ask a sales assistant for advice.
Polishing a concrete floor with an orbital sander requires a combination of good prior knowledge and the correct tools and accessories. With some patience, time, and a lot of effort, you can achieve a beautifully smooth polished surface.