Pick the wrong abrasive blasting grit and you pay for it twice: once at the supplier, and again in failed coatings, substrate damage, or disposal costs that dwarf what you saved on the bag price.

Before you evaluate any specific media, answer these five questions about your job. Each one eliminates candidates from the list — by the time you reach the last question, the right media is usually obvious.

Question 1: Surface preparation or cleaning?

This is the most important question you will answer. Surface preparation means removing contaminants and creating an anchor profile — a mechanical key that gives coatings something to grip. Cleaning means removing contaminants while leaving the substrate dimensionally and texturally intact.

That distinction drives the single most important variable in media selection: particle shape. Angular media cuts into the surface on impact, creating the jagged peaks and valleys a coating needs to bond. Spherical or rounded media peens the surface instead, producing a smooth, dimpled finish with no sharp peaks — right for cleaning, shot peening, and finishing work, but wrong for any job where a coating must adhere.

Question 2: Do you need a recyclable media?

Recyclability is the biggest single driver of running cost, and most buyers underestimate it because they anchor on purchase price per bag.

Media such as steel grit, steel shot, aluminium oxide, and garnet can all be reclaimed and reused across multiple cycles, spreading the purchase cost over a much larger area of prepared surface. Slag media — coal slag and copper slag — are effectively single-use: high friability means particles shatter on impact and cannot be economically recovered. A higher per-bag price for a recyclable media can be offset many times over by those reuse cycles, provided you have a reclaim system in place to capture it.

Question 3: How dust-sensitive is your environment?

Friability — how readily a media shatters into fine dust on impact — varies significantly across media types, and it has real consequences beyond housekeeping.

High-friability media such as slag and lower-quality garnet generates substantially more airborne dust than tougher, harder media. That dust affects worker health and exposure limits, reduces visibility inside a blast room (cutting productivity and raising safety risk), and creates compliance obligations on open sites or wherever other workers are nearby. Dust generation is a genuine selection criterion, not a footnote.

Question 4: What surface profile does your coating specify?

Coating systems are engineered to bond to a specific surface profile — typically specified in mils or microns — and the media must deliver a profile within that range.

The directional logic is straightforward: coarser, harder, more angular media produces deeper, more aggressive profiles; finer or spherical media produces shallower, smoother ones. Exceed the specified profile and you waste coating material filling deeper peaks and valleys. Fall short and you risk delamination — the coating lacks sufficient mechanical key to hold. This is the question that connects media selection directly to coating performance, so treat it as an engineering constraint, not a preference.

Question 5: How sensitive is your substrate?

Not every substrate can tolerate aggressive angular media, and substrate sensitivity can disqualify an otherwise suitable media outright.

Three categories demand particular care: non-ferrous metals (aluminium, copper alloys, stainless steel) are at risk of ferrous contamination if metallic media is used; thin-walled or precision components cannot absorb the dimensional change that aggressive profiling causes; and heritage or restoration materials — stone, masonry, decorative metalwork — require media gentle enough to clean without compromising surface integrity. If your substrate falls into any of these categories, several media types are off the table before you read a single spec sheet.

With the five questions answered, the final lens to apply is economic: total running cost, not purchase price per bag. The relevant calculation is cost-per-square-metre of surface prepared, which accounts for media consumption rate, reuse cycles, disposal costs for spent single-use media, and the productivity gains from faster-cutting media that finishes the job sooner.

With these five questions answered, the entries below give you the specific properties of each media type — hardness, particle shape, profile range, recyclability, and typical applications — to match directly against your requirements.

Both steel grit and steel shot are manufactured cast steel products — not industrial by-products — with a tempered martensite microstructure that resists deformation on impact and delivers consistent, repeatable results.

Hardness is selectable across four SAE grades (S, M, L, and H), letting operators dial in the right aggressiveness for their substrate and finish requirement — a level of control that single-use media simply cannot offer.

Steel Grit

Angular in shape, steel grit cuts into the surface on impact rather than bouncing off it, creating a deep, jagged anchor profile suited to high-build industrial coatings that need a strong mechanical key.

Primary applications include structural steel fabrication, bridges, railcars, pipelines, and blast rooms — anywhere a coarse, aggressive surface texture is the goal and a reclaim system is in place to recover the media.

Steel Shot

Spherical in shape, steel shot peens the surface rather than cutting it, producing a dimpled, lower-profile finish without the sharp peaks that grit leaves behind.

This makes shot the right choice for general blast cleaning, descaling, and — critically — shot peening, where the goal is to induce compressive stress in metal components to improve fatigue strength, not to create an anchor profile.

Shot peening is specified across automotive and aerospace component preparation, where controlled intensity and coverage are as important as cleanliness.

Both variants share the same exceptional reusability: the Clemco Infotools chart rates both steel grit and steel shot at 200+ reuse cycles in reclaim systems, making the per-use cost among the lowest of any abrasive blasting media over a full lifecycle.

Near dust-free operation is another shared advantage. According to the EPA, total particulate matter emissions from blasting with grit run at roughly 24% of those from sand blasting — and shot drops that further, to around 10%.

The critical limitation of both media is ferrous contamination risk: embedded iron particles from carbon steel media can cause galvanic corrosion on aluminium, stainless steel, and other non-ferrous substrates, making both grit and shot unsuitable for those surfaces.

The 200+ cycle economics also depend entirely on having a reclaim system in place. Without one, the cost advantage disappears and the case for metallic media weakens considerably.

Like steel grit, aluminium oxide is angular — but unlike metallic media, it carries zero ferrous contamination risk, making it the go-to choice when substrate sensitivity rules out steel entirely.

Composition and Manufacture

Brown fused alumina (Al₂O₃) is produced by electrofusing bauxite in electric arc furnaces — a purpose-engineered abrasive, not a mineral or an industrial by-product.

That manufacturing origin matters: it gives aluminium oxide a level of compositional consistency and grit-size precision that naturally occurring or slag-derived media simply cannot match.

Hardness: The Defining Characteristic

At Mohs 9, aluminium oxide is the hardest commonly used non-metallic blasting abrasive — harder than all slag media, harder than garnet, and harder even than steel grit on the Mohs scale.

That hardness advantage is not merely a spec-sheet number: it translates directly into faster cutting at lower blast pressures, more efficient removal of hard oxides and mill scale, and a sharper, more well-defined anchor profile.

The wide grit size range — macro sizes 12 through 240 — means profile depth is highly controllable, from fine etching at tight tolerances to deep anchor patterns for high-build coatings.

Primary Applications

Aluminium oxide is the benchmark abrasive for precision surface preparation across several demanding industries.

• Thermal spray coating preparation: The standard choice for oil and gas pipeline preparation, where a sharp, consistent anchor profile is critical for coating adhesion.
• Aerospace component preparation: Used in aircraft engine overhaul and aerospace part finishing, where ferrous contamination from metallic media is unacceptable.
• Investment casting cleaning: Removes ceramic shell residue from cast components without contaminating the substrate.
• Hard oxide and mill scale removal: High hardness makes it effective where softer media would slow down or require higher pressures.
• Glass etching and precision surface prep: Fine grit sizes allow controlled, repeatable etching on sensitive or decorative substrates.

The common thread across these applications is the need for a controlled, contamination-free surface — conditions where aluminium oxide's combination of hardness, angular shape, and non-ferrous composition is difficult to replace.

Brown vs White Grade: Which to Specify

Not all aluminium oxide is identical — the grade distinction is a genuine selection decision point, not a marketing distinction.

• Brown fused alumina (96% Al₂O₃): The general industrial standard. Suitable for the vast majority of blasting applications, including thermal spray prep, aerospace, and oxide removal. This is what most suppliers mean when they list aluminium oxide blasting media.
• White fused alumina (99.5%+ Al₂O₃): Specified where surface contamination must be completely eliminated — medical devices, electronics manufacturing, and food-contact surface preparation. Higher purity comes at a higher price; use it only when the application genuinely demands it.

For most industrial blasting tasks, brown fused alumina is the correct specification; white fused alumina is a niche choice driven by contamination-sensitivity requirements, not performance.

Reusability, Recyclability, and Running Cost

Aluminium oxide typically delivers 6–8 passes through a reclaim system before particle breakdown reduces its cutting efficiency — a meaningful reuse cycle that spreads the higher per-bag purchase price across multiple runs.

Beyond reclaim reuse, spent aluminium oxide can be returned to the manufacturer for closed-loop recycling, reducing disposal costs and waste volumes compared to single-use slag media.

That said, realising the reusability advantage requires a reclaim system: operators running aluminium oxide on a single-use basis absorb the full purchase price premium without the offsetting cycle economics.

Garnet is a natural mineral abrasive — specifically the almandine variety (Fe₃Al₂(SiO₄)₃) — mined and processed rather than manufactured from industrial by-products or synthetically fused like aluminium oxide.

It occupies a deliberate middle ground in the abrasive landscape: harder and denser than slag media (Mohs 7.5–8.0 vs. slag's 6–7), yet softer than the aluminium oxide covered in the previous entry, and far more affordable than metallic abrasives on a per-project basis.

The defining physical characteristic of almandine garnet is its sub-angular particle shape — sharp enough to cut efficiently and generate a proper anchor profile, but not so aggressively angular that it embeds in the substrate or leaves rogue peaks that consume excess coating.

This balance between cutting speed and surface consistency is what separates garnet from both slag (which can embed due to its fractured, horn-like structures) and aluminium oxide (which is more aggressively angular and harder to control on profile depth).

Grade selection determines the surface profile produced, and the relationship is direct: coarser grades produce deeper profiles for heavy maintenance work, while finer grades deliver shallower, tighter profiles suited to new steel preparation.

The 30/60 grade is the industry-standard general-purpose choice for most maintenance and new-construction blasting — the grade designation means particles pass through a 30-mesh screen and are retained on a 60-mesh screen, producing a consistent particle size band.

The 80 mesh grade is the preferred option for fast mill-scale removal on new steel, where its finer particle size delivers high blasting rates (up to 35 m²/hr) at low consumption, and the shallower 40–55 µm profile suits thin-film coating systems.

Where Garnet Is the Professional Default

Garnet has become the de facto standard abrasive blasting grit in several professional settings where the combination of low dust, consistent profile, and no ferrous contamination risk is non-negotiable.

• Shipyard blasting: Hull and superstructure work in enclosed or semi-enclosed environments where dust control directly affects worker safety, visibility, and productivity in confined spaces.
• Oil and gas infrastructure: Tanks, pipelines, and offshore platforms — applications requiring compliance with regulated surface preparation standards and consistent, measurable anchor profiles.
• Structural steel maintenance: Bridge and industrial structure recoating where a uniform, rogue-peak-free profile reduces coating consumption and extends service life.
• Non-ferrous substrate blasting: Aluminium, stainless steel, and other non-ferrous surfaces where metallic abrasives must be excluded entirely to prevent ferrous contamination and corrosion.

Garnet is also the natural choice for blast-room recycling operations, where its moderate reusability — typically three to five turns with a reclaim system — makes it substantially more economical than single-use slag on a cost-per-square-metre basis.

Garnet's reusability sits well above single-use slag (which shatters on impact and cannot be meaningfully recycled) but well below metallic abrasives, which can run 200+ cycles in a reclaim system.

For regulated and professional applications, garnet meets U.S. Navy MIL-A-22262B(SH) and SSPC-AB 1 (Type 1, Class A) standards — compliance markers that matter when working to government, naval, or major coating specification contracts.

Garnet Limitations

Garnet carries a higher per-bag purchase price than slag media — but as the total-cost data above shows, this premium is typically recovered through lower consumption, reduced disposal costs, and faster cycle times.

For the most demanding profiling tasks — extremely hard mill scale or applications requiring maximum cutting aggression — aluminium oxide's Mohs 9 hardness gives it an edge that garnet cannot fully match.

The most important practical caveat for buyers is supplier quality variation: not all garnet performs equally.

Independent respirable dust testing shows premium almandine garnet generating 0.078–0.325 mg/m³, while other garnets measured 0.175–0.488 mg/m³ — a meaningful difference in worker exposure and regulatory compliance that buyers sourcing lower-cost alternatives should factor in.

Glass bead is a spherical, chemically inert blasting media whose peening action produces a bright, satin surface without cutting into the substrate — a fundamentally different outcome from the angular media covered in the previous three entries.

Glass Bead Composition and Properties

Glass bead is manufactured from soda-lime glass — either virgin materials or recycled glass cullet — and carries no free silica, no lead, and no metallic iron.

Its hardness sits at approximately Mohs 5.5–6.0 (Vickers ~645), placing it well below garnet (Mohs 7–8) and substantially below aluminium oxide (Mohs 9). That relative softness is a deliberate advantage: it means gentler action on the substrate, making glass bead safe for stainless steel, aluminium, and precision components where harder angular media would cause unwanted material removal.

The spherical shape is the defining characteristic. Where angular particles cut and fracture the surface to create a jagged anchor profile, spherical particles strike and rebound — producing a dimpled, compressive finish with a consistent satin sheen and no dimensional change to the substrate.

Glass Bead Applications

Glass bead's applications share a common thread: each requires a clean, bright finish without surface profiling, and/or a substrate that cannot tolerate ferrous contamination or dimensional change.

• Food-processing equipment and abattoir machinery: Iron-free media with no toxic residue — safe for surfaces that contact food or require strict hygiene standards.
• Automotive restoration: Delivers a bright cosmetic finish on body panels, trim, and engine components without altering part dimensions.
• Stainless steel platforms, walkways, and fabrications: No ferrous contamination risk, preserving the corrosion resistance of austenitic stainless steel.
• Mould cleaning: Removes light residue and release-agent build-up without changing mould geometry or surface tolerances.
• Light-to-medium shot peening: Imparts compressive stress on precision components such as springs and gears, improving fatigue strength and reducing notch sensitivity.
• Carbon and heat-treat scale removal: Cleans scale from precision components without the aggressive cutting action of harder angular abrasives.

A single glass bead pass can clean, finish, peen, and deburr simultaneously — what suppliers describe as a four-in-one action — which reduces process steps on components that would otherwise require separate operations.

Sizing runs from #20–30 (coarser, for faster cleaning and heavier peening) through to #270 and finer (for smooth cosmetic finishes), with mil-spec sizing available for shot peening applications where precise particle distribution is specified.

In terms of reusability, glass bead achieves approximately 8–10 cycles in controlled blast-cabinet environments. Its spherical shape resists breakdown better than angular media of comparable hardness, because there are no sharp edges to fracture off on impact — making running cost per cycle moderate.

Processing pressure should not exceed 4 bar: above this threshold, particle breakdown accelerates sharply, shortening reuse life and increasing dust generation.

Glass Bead Limitations

Glass bead produces a low, smooth surface profile — which is precisely correct for finishing and cleaning work, but disqualifying for coating preparation on structural steel where a deep anchor pattern is specified.

Its lower hardness also means slower progress on heavy rust, thick coatings, or tenacious mill scale: glass bead is a finishing and light-cleaning media, not a heavy-duty stripping tool.

Where a stainless steel or aluminium substrate requires a surface profile — for example, to key a thermal spray coating — aluminium oxide (covered in Option 2) is the correct media choice, not glass bead.

Coal slag and copper slag are the only industrial by-products in this comparison — not manufactured abrasives, not mined minerals, but vitrified waste materials crushed and sized for blasting.

That origin defines their economics: low purchase price per bag, wide availability (especially coal slag), and zero recyclability — they shatter on impact and cannot be reclaimed.

The angular particle shape is the performance core of both media — it cuts into steel surfaces and creates a workable anchor profile for coatings, unlike the peening action of spherical media such as glass bead.

Profile consistency, however, is not slag's strong suit: moderate particle embedment is a known characteristic, and profile uniformity is less controlled than what garnet or aluminium oxide deliver.

Single-Use Economics: The Real Cost Calculation

High friability is the defining mechanical limitation of both slag types — particles shatter on impact, generating fines that cannot be reclaimed, making every blast a one-way consumption event.

The Clemco abrasive comparison chart rates mineral slag at just 1–2 cycles, versus 200+ for steel grit and 6–8 for aluminium oxide — a gap that changes the cost-per-square-foot calculation substantially once disposal and volume consumption are factored in.

Disposal of spent slag media may require hazardous waste classification depending on jurisdiction — a cost dimension that buyers focused on purchase price often miss entirely.

Slag is genuinely cost-effective for large outdoor projects where a reclaim system is not feasible and throughput matters more than per-use efficiency — the economics only break down when disposal costs and volume consumption enter the calculation.

Health and Environmental Limitations

Both media carry a documented hazardous air pollutant profile that goes beyond the free-silica risk that drove the original shift away from silica sand.

NIOSH Phase 2 field data found that coal slag produced greater geometric mean airborne concentrations than silica sand for all hazardous health-related agents tested except respirable quartz — including the highest concentrations of beryllium and vanadium among all abrasive categories studied.

For copper slag, the EPA Serageldin emissions study documented particulate lead emission factors (48.3 mg/kg abrasive) substantially higher than silica sand (0.232 mg/kg), and OSHA shipyard guidance notes that blasting with copper slag can generate arsenic, chromium, and lead levels that exceed OSHA Permissible Exposure Limits.

A NIOSH health hazard evaluation at a coal and copper slag processing facility found that copper slag processing produced higher levels of dust, silica, and metals than coal slag processing — and that five of six workers sampled at the copper slag facility were exposed to arsenic that approached or exceeded the OSHA PEL.

OSHA guidance notes that coal slag may cause lung damage similar to silica sand based on preliminary animal testing, and that slags can contain trace amounts of arsenic, beryllium, and cadmium.

These are documented regulatory findings, not fringe concerns — buyers and contractors should consult OSHA and EPA guidance and review the manufacturer's Safety Data Sheet before specifying either media, particularly for enclosed or semi-enclosed blasting environments.

Substrate Limits and When to Choose Slag

Neither coal nor copper slag is recommended for stainless steel or aluminium — ferrous contamination risk and the aggressive angular profile make both unsuitable for these substrates.

Slag earns its place on large-scale outdoor blasting of carbon steel and concrete where purchase price and availability dominate the decision, reclaim is not an option, and the site conditions support proper respiratory protection and waste management.

Copper slag's harder cutting action (Mohs 7.0–7.5 vs coal slag's 6.0–7.0) can be an advantage on heavy rust or thick coatings, but its regional availability near copper refineries makes it a less universal choice than coal slag for buyers outside the US Gulf Coast.

Particle shape is the clearest guide: angular, recyclable media for jobs requiring a surface profile; spherical media for cleaning and finishing where profiling would cause harm; slag only where single-use economics make it the pragmatic call.

The per-bag price is the least useful number on the invoice — reusability, dust management, and disposal costs determine what you actually spend.

If your job involves precision components, heritage materials, or a site where containing blasting media is difficult, Woodrow Scientific's ELASER-RHZ offers consumable-free laser cleaning with the world's first reduced hazard zone technology — no sealed-off area required.