Choosing the right abrasive for sandblasting isn't just a technical detail: it makes the difference between a flawless finish and one that leaves something to be desired. It's not just about "cleaning" or "roughing"; it's about understanding what the surface really needs, how we want it to look, and what it will be used for later. Every little bit counts.
There are many options available on the market. Some sound more familiar—such as bicarbonate, corundum, or glass microspheres—but others are equally useful, depending on the case: steel or stainless steel shot, garnet sand, walnut shell, or even ceramic. Each has its own advantages, limitations, and very specific uses.
Which abrasive should you choose depending on the type of surface?
The first step, and perhaps the most important, is to take a good look at the material you're going to treat. Is it fragile? Is it resistant? An abrasive that's too harsh can mark or deform the piece. A very soft one, on the other hand, won't do much on a hard surface. So it's not a question of going all out, but rather getting it right.
Sodium bicarbonate
When care and precision are needed.
- Ideal for thin aluminum, fiberglass or plastic parts.
- Works well on chrome or glass surfaces.
- Perfect for heritage restorations, soot or light soiling.
However, it doesn't leave any roughness, so if you're going to paint afterwards, it's a good idea to go one step further with another abrasive. It's single-use and must be rinsed well, as it leaves alkaline residue.
Corundum (aluminum oxide)
Hard as few (Mohs hardness 9), and with an angular shape.
- To remove strong oxides or calamine on steel.
- Excellent for removing tough coatings.
- Widely used to prepare surfaces before applying paint or industrial coatings.
It creates a texture that helps coatings adhere better. And the best part: it's reusable.
Glass microspheres
When you're looking for a beautiful, even, scratch-free finish.
- They work very well on aluminum and stainless steel, such as in machinery or nautical furniture.
- They clean and satin evenly.
- They are also used for light shot peening (a technique that improves the strength of the metal).
They leave no anchoring profile and can be reused.
Steel shot
Ideal for large carbon steel structures.
- High cutting capacity.
- Very efficient if working in booths with a continuous recycling system.
Caution: Do not use on stainless steel, as it may contaminate it and cause rust.
Stainless steel shot
Same principle as above, but without the risk of cross-oxidation.
- Perfect for stainless steel, aluminum or non-ferrous metals.
- Reusable many times.
Garnet sand
A mineral abrasive with intermediate hardness and quite a bit of versatility.
- Suitable for steel, stone and concrete.
- Good balance between cutting and finishing ability.
- It is also used in water jet cutting.
Nutshell
An ecological and very delicate option.
- Perfect for cleaning without damaging: carved wood, engines, aeronautical parts.
- Does not attack soft metals or wear down the base.
- Biodegradable.
Ceramics
Very resistant, designed for technical processes.
- Lasts much longer than other abrasives.
- It is used where constant and repetitive precision is needed.
Which abrasive should you choose depending on the desired finish?
Just as important as cleanliness is the final texture. Do we want the paint to adhere well? Or just leave the surface looking like new, without scraping?
Profile-free finish (without leaving roughness)
- Baking soda: cleans without modifying the original surface.
- Glass microspheres: leave an elegant satin finish, especially on stainless steel or aluminum.
- Walnut shell: perfect for fragile or soft surfaces.
Finished with anchoring profile (for better adhesion of paint or coating)
- Corundum: fast, precise and with good roughness.
- Steel or stainless steel shot: aggressive profile, ideal for industrial environments.
- Garnet sand: leaves a good profile without being too abrasive.
Special or technical finishes
- Ceramics: for processes where everything must be perfectly uniform and controlled.
- Shot peening: with microspheres or spherical shot, to increase the metal's fatigue resistance.
Common mistakes when choosing abrasive
A mistake at this stage can be costly or ruin the entire job. Some common mistakes:
- Using too much pressure or a very aggressive abrasive on thin sheets and deforming them.
- Contaminate stainless steel with steel particles.
- Painting over a piece treated with baking soda without rinsing well.
- Expect the walnut shell or microbeads to create roughness (spoiler: they don't).
- Use steel shot on aluminum or stainless steel and end up rusting it.
Technical details that also influence
It's not just the type of abrasive. There are other factors at play:
- Grit size: The finer the grit, the smoother the finish. If it's coarse, it cuts harder.
- Pressure: more pressure, more aggressive… but also more risk if not controlled.
- Impact angle: 90° cuts more; at low angles, cleaning is smoother.
- Recyclability: Some abrasives last longer than others. Corundum, microspheres, and shot last quite a while; bicarbonate and shell, much less so.
Real cases: which abrasive should you choose?
- Classic car restoration: baking soda or walnut shells to avoid damaging the sheet metal.
- Steel boat hull: corundum or garnet sand, to remove rust and prepare the surface.
- Stainless steel machinery: stainless steel microspheres or shot, for a clean and uniform finish.
- Carved wood: walnut shell, for its softness.
- Large metal structures: steel shot, for speed and performance.
- Technical treatments: ceramic or microspheres, depending on the process.
Sandblasting experts in Mallorca
At Projectes Sastre We have been working with for years sandblasting in Mallorca, in sectors as diverse as nautical, automotive, industrial, construction, and heritage restoration. We know that every surface has its history, wear, and future purpose. That's why we don't always use the same thing.
We offer a wide variety of abrasives: bicarbonate, corundum, glass microspheres, shot (steel and stainless steel), garnet sand, walnut shell, and ceramic. This allows us to tailor the treatment to each project without compromising the result.
Do you need advice or a professional sandblasting service in Mallorca? Write to us. We'll study your case, select the most suitable abrasive, and work with precision equipment to ensure your surface is ready for whatever comes next.
