White fused aluminum oxide for sandblasting glass products
What is White Fused Aluminum Oxide (WFA)?
It is a synthetic abrasive produced by melting high-purity alumina (Al₂O₃) in an electric arc furnace and then cooling and crushing it into precise grain sizes. It is characterized by:
- Extreme Hardness: 9.0 on the Mohs scale (diamond is 10). This makes it much harder than glass (~5.5-7 Mohs).
- Sharp, Blocky Grains: The grains are angular, which provides a sharp, cutting action.
- High Purity: Typically >99% Al₂O₃, meaning it introduces very little contamination.
Advantages for Glass Sandblasting
- Superior Cutting Speed: Its hardness and sharpness allow it to etch, frost, or carve glass very quickly and efficiently compared to softer abrasives.
- Excellent Finish Quality: It produces a clean, consistent, and bright white matte (frosted) finish on glass. This is highly desirable for decorative and architectural applications.
- Low Contamination (Iron-Free): This is a critical advantage. White fused aluminum oxide contains no free iron. Unlike some lower-quality abrasives (like certain brown aluminum oxides or slag abrasives), it will not leave rust stains or embedded iron particles on the glass surface, which can cause discoloration over time.
- Durability and Reusability: It is a very tough abrasive that fractures into smaller, sharp pieces rather than turning to dust. This allows it to be recycled multiple times within a closed-loop blasting system, making it more cost-effective for high-volume operations.
Disadvantages and Considerations
- Cost: It is one of the most expensive blasting abrasives available. The initial investment is high.
- Aggressiveness: Its hardness can be a drawback. If not carefully controlled, it can remove more material than intended or create too deep a profile. It requires a skilled operator.
- Not for Thin Films or Delicate Work: It is generally too aggressive for simply removing a thin coating from glass without risking damage to the substrate.
- Dust Generation: Like all fine abrasives, it creates significant dust, requiring excellent dust collection and operator PPE (Respirator, protective suit).
Key Application Parameters for Glass
To get the best results, you must control these variables:
Parameter | Recommendation & Impact |
|---|---|
Grit Size | Fine to Medium Grits are most common. • #80 – #120: For a standard, uniform matte finish. A good starting point. • #180 – #220: For a lighter, smoother “satin” finish. • #36 – #60: For deeper etching, carving, or logo marking. • #220 and finer: For very light frosting or creating subtle textures. |
Air Pressure (PSI/Bar) | 40 – 100 PSI (2.8 – 6.9 Bar). Lower pressures (40-60 PSI) are used for light frosting and to prevent excessive glass removal. Higher pressures (80-100 PSI) are for deep etching and faster cutting. |
Nozzle Distance & Angle | 6-18 inches (15-45 cm) at a 45-90 degree angle. A greater distance and a more oblique angle will create a lighter, more diffuse frost. A closer distance and a 90-degree angle will create a deeper, more defined etch. |
Abrasive Feed Rate | Must be consistent. An uneven feed will result in a blotchy, uneven finish. |
Stencil Material | Due to the abrasive nature of WFAO, you need high-quality, durable stencils. Self-adhesive vinyl or rubber stencils are necessary to achieve sharp, clean edges on designs. Paper stencils will be cut through quickly. |
Typical Applications on Glass
- Decorative Frosting: Creating patterns, logos, and artwork on glass panels, doors, and partitions.
- Architectural Glass: Frosting glass for privacy in bathrooms, offices, and facades.
- Labeling/Serialization: Permanently etching serial numbers, logos, or text onto glass products.
- Lighting: Frosting glass shades and globes to diffuse light.
- Preparation for Coating: Creating a mechanical anchor profile on the glass surface before applying ceramic paints or other coatings (less common, as glass is often smooth-coated).