The Purpose of Restoration Blasting
- HISTORIC FABRIC / PRESERVATION — leaving the surface pattern, the carving and the relief undisturbed
- GRIME, DIRT, CARBON, RUST — cleaned off the surface
- PAINT REMOVAL — returning an old painted surface to its original state
- MOSS AND BIOLOGICAL GROWTH — cleaning wall, sculpture and rock surfaces
- POLLEN AND DUST DEPOSITS — long-term atmospheric contamination
Industrial Versus Restoration Blasting
Industrial Sandblasting
- Objective: aggressive surface roughening
- Abrasive: garnet, aluminium oxide (hard)
- Pressure: 5-8 bar (high)
- Mesh: coarse (16-30)
- Time: fast, focused on output
- Change to the surface: it alters the original structure
Restoration Sandblasting
- Objective: gentle cleaning, preserving the fabric
- Abrasive: glass bead, soda, walnut shell
- Pressure: 0.5-2 bar (very low)
- Mesh: fine (60-200)
- Time: slow and careful
- Change to the surface: the original structure is preserved
Restoration Abrasives
| Abrasive | Hardness (Mohs) | Application | Notes |
|---|---|---|---|
| Glass bead | 5.5 | Light cleaning | Round grain, deformation rather than abrasion (shot peening) |
| Soda (sodium bicarbonate) | 2.5 | Very delicate surfaces | Water-soluble, friendly to the ecosystem |
| Walnut shell | 3-4 | Antique timber, delicate restoration | Organic and soft |
| Dry ice (CO₂) | — (dry ice) | Industrial cleaning, no toxic waste | It sublimates, leaving no waste |
| Plastic media | 3-4 | Delicate metal surfaces | Aluminium, thin sheet |
| Corn cob | 3 | Very soft, antique timber | Gentle abrasion |
Restoration Approaches
Soda Blasting
- Sodium bicarbonate (baking soda) — soft and water-soluble
- For the most delicate surfaces (timber, aluminium, stainless steel)
- Rinsed away with water → waste management is straightforward
- Environmentally friendly — no problem for soil or water
- Typical for classic cars, old furniture and historic sculpture
Dry Ice Blasting
- CO₂ pellets — they sublimate (turn into gas), leaving NO waste
- Thermal shock loosens the dirt and the mechanical impact lifts it away
- Delicate electronics, cleaning inside machinery
- It does not affect the historic fabric at all (the gentlest method)
- Expensive, but ideal for complex work because there is no waste to manage
Glass Bead
- Round glass grain — it polishes the surface by deformation
- Not abrasion but a shot peening effect (the surface work-hardens)
- Antique metal, machine parts, aluminium
- Gives the surface a matt finish and a sheen
- A hybrid of industrial and restoration use
Cleaning the Surfaces of Historic Buildings
Cleaning the facade of a mosque, a church or a historic house calls for particular expertise:
- Analyse the surface first — the type of stone, and any earlier treatment
- A test area — a trial on a small patch
- Choice of abrasive — matched to the hardness of the stone (usually soda or a very fine mesh)
- Low pressure (0.5-1 bar) — so the stone surface is not cut away
- A careful operator — constant control of distance and angle
- Supervision by a restoration architect — approval of the scope and the method
- Documentation of the result — before and after photographs plus a treatment report
Restoring Sculpture and Works of Art
- Detailed surface mapping — the areas under protection are marked
- Surface patterns of value (relief, carving) are preserved
- A soft abrasive (soda, walnut shell) — it cleans the surface within seconds
- Worked by hand — the operator moves the gun around the piece under control
- Constant checking — over-blasting is stopped the instant it appears
- Final finishing by hand — a brush and meticulous cleaning wherever possible
The Legal and Ethical Framework
- A registered cultural asset — permission from the Ministry of Culture is required in Türkiye
- Supervision by a restoration architect is mandatory
- Museum objects — a dedicated specialist plus a scientific adviser
- Documentation before and after treatment (the international standard — the ICOMOS guidelines)
- Irreversible loss — a single operator error can destroy the piece
- Insurance and liability — heritage work carries the risk of compensation claims at high values
The Operator Training Requirement
Restoration blasting demands five to ten times the training of industrial blasting:
- A grounding in art history and materials
- The effect of the various abrasive and pressure combinations
- Restoration ethics and the international standards
- Site practice (large-scale work)
- Micro-working (the detail of sculpture)
- Certification — a legal requirement in some countries