What Is Sand Blasting? The Process, Step by Step

What is sand blasting? The process, step by step

Sand blasting is abrasive blasting: compressed air drives an abrasive through a hose and a nozzle at a surface, to strip rust, mill scale or old coating and to leave a rough profile that paint can grip. The job runs in five steps: inspect, set up the blast line, blast, check the finish, then coat.

Flexihose sand blast hose: 175 PSI / 12 BAR working · 700 PSI / 48 BAR burst · 1/2" to 2" bore · DIN abrasion loss below 60 mm³ · Exceeds IS 5894

What is sand blasting?

Sand blasting is the process of firing a stream of abrasive particles at a surface with compressed air, to clean it, strip it or change its texture. The US Occupational Safety and Health Administration describes abrasive blasting as directing “a high velocity stream of an abrasive material” at an object to clean it, remove burrs, apply a texture or prepare it for paint (OSHA fact sheet, Protecting Workers from the Hazards of Abrasive Blasting Materials).

The Canadian Centre for Occupational Health and Safety lists the same jobs: cleaning, removing paint and other coatings, removing rust, adding texture to a smooth surface and smoothing a rough one (CCOHS, Abrasive Blasting (Sandblasting)). This guide concentrates on the industrial job: taking steel back to clean metal before it is painted.

The name is older than most of today’s practice. Benjamin C. Tilghman patented the method in the United States on 18 October 1870, as an improvement in cutting and engraving stone, metal and glass (US Patent 108,408), and silica sand was the usual abrasive for a long time after. Most industrial blasting now uses other media, and in Indian factories silica sand may not be used at all. The work is still called sand blasting, whatever goes into the pot.

The sand blasting process in five steps

Every sand blasting job, from a single casting to a storage tank, runs through the same five steps in the same order. The equipment changes with the size of the job; the sequence does not.

1. Inspect the surface. Clean off oil and grease, then record the starting condition. ISO 8501-1 sorts uncoated steel into four rust grades, A to D, and the grade you start from decides which reference the finished surface is later judged against (ISO 8501-1:2007).
2. Set up the blast line. Compressed air passes through a moisture separator into the blast pot, where abrasive is metered into the air stream. The mix travels along the blast hose to the nozzle, and a deadman control at the operator’s hand stops the flow the moment it is released. Each part is explained in our guide to the parts of a sand blasting machine.
3. Blast. The operator works the nozzle across the surface in steady, overlapping passes so the whole area gets the same treatment. The pressure that does the work is the pressure at the nozzle, not the gauge at the compressor, and it falls along every metre of line. Matching the two is covered in sizing the compressor and nozzle for sand blasting.
4. Check the finish. The blasted surface is compared against the grade the coating specification calls for, such as Sa 2.5 on structural steel. How that grade is judged and signed off is set out in our Sa 2.5 surface preparation guide.
5. Coat. Remove the blast dust, then prime before the clean steel starts to rust again. The coating manufacturer’s data sheet sets how long that window is on your site.

Types of sand blasting

Sand blasting systems differ in three ways: how the abrasive is fed into the air, whether water is added, and where the work is done. Any one job combines one choice from each.

Pressure blasting and suction blasting

In a pressure system the abrasive sits in a sealed pressure vessel, the blast pot, and is forced into the air stream and out of the nozzle. In a suction, or siphon, system the air rushing through the gun creates a vacuum that draws abrasive up from a hopper, which is the Venturi principle. IST International Surface Technologies, a blast equipment maker, notes that the air jet in a suction gun is about half the nozzle’s bore, which is why a pressure system delivers abrasive at a much higher velocity and cleans faster, while a suction system uses its compressed air more efficiently and costs less (IST, suction or pressure). IST recommends pressure systems for large-volume, aggressive cleaning.

Dry blasting and wet blasting

Dry blasting uses abrasive and air alone. Wet blasting adds water to the stream. OSHA lists abrasives delivered with water, as a slurry, among the ways to reduce dust, and CCOHS names wet blasting as a separate form of blasting. The Flexihose sand blast hose is built for both: its catalogue application is cleaning and blasting with wet or dry sand or other abrasive material.

Open blasting, blast rooms and cabinets

Large structures are blasted in the open or in a blast room. Smaller parts go into a cabinet. CCOHS notes that a blasting cabinet suits relatively small workpieces and protects all workers, while a blasting room or booth contains the dust and protects bystanders but still leaves the operator exposed.

Sand blasting vs abrasive blasting

They are the same process. Abrasive blasting is the accurate name, because the abrasive can be steel grit, steel shot, garnet, copper slag, glass bead or aluminium oxide. Sand blasting is the older name, from the years when silica sand was the default, and it is still the name most people search for. CCOHS files the whole subject under a single heading, “Abrasive Blasting (Sandblasting)”.

Shot blasting is a close relative that fires round steel shot, and grit blasting uses angular steel grit. The three are compared side by side in our guide to shot, sand and grit blasting.

What a sand-blasted finish looks like

A sand-blasted finish is set by the shape of the abrasive more than by the machine. Angular abrasives such as steel grit, garnet and copper slag cut into the surface and leave a sharp, matte texture, the rough anchor profile a coating needs to grip. Round media such as steel shot and glass bead strike without cutting and leave a smoother, peened or satin surface.

How rough the anchor profile must be is part of the coating specification, and it is measured rather than judged by eye. The Sa 2.5 guide linked above explains how the grade and the profile are checked together.

What can be sand blasted?

Almost any hard surface can be sand blasted, as long as the abrasive and the pressure suit it. The common ones:

• Structural steel and fabrications: rust, mill scale and old paint removed before a new coating.
• Castings: cleaned after casting, before machining or coating. The catalogue application for the Flexihose sand blast hose names casting metal first.
• Concrete: cleaned, stripped of old coatings or roughened so a new coating or waterproofing bonds. The profile grades that go with each job are in sand blasting concrete.
• Stone and granite: matte and anti-skid textures, and stencilled lettering, set out in granite sand blasting. Tilghman’s 1870 patent was for engraving stone.
• Aluminium, glass, plastic and wood: lighter work, usually in a cabinet, with an abrasive chosen so it does not damage the surface.

Why sand blasting is done

Sand blasting does two jobs at once. It removes rust, mill scale and old coatings down to clean metal, and it leaves the surface rough enough for the next coating to bond.

ISO 8501-1 lists blast-cleaning alongside hand and power tool cleaning and flame cleaning as ways to prepare steel for painting, and notes that these methods “rarely lead to comparable results”. When a coating specification names a blast-cleaned grade, such as Sa 2.5, it fixes both the method and the result.

Is sand still used for sand blasting?

Not in Indian factories. Rajasthan’s Factories (Amendment) Rules 2025, notified on 27 October 2025 as G.S.R. 86, state that sand or any other substance containing free silica “shall not be introduced as an abrasive into any blasting apparatus” (Rajasthan Gazette, Factories and Boilers Inspection Department). Gujarat’s Factories Rules carry the same prohibition in their schedule for blasting operations.

The reason is silicosis. CCOHS notes that breathing in silica sand media can cause silicosis and lung cancer. Steel grit and shot, garnet, copper slag, aluminium oxide and glass bead do the work instead. You can read the silica rules in full, including who they cover and the exemption route. Which abrasive goes in instead, and what OSHA states about the health risk of each, is in our guide to choosing a sand blasting media.

The blast hose: where the abrasive wears the line

Every grain that reaches the surface has first travelled the length of the blast hose, and it scours the lining on the way. A blast hose is therefore specified on two numbers: the pressure it holds, and how much lining it loses to abrasion.

Flexihose India (FLEXI HOSE), a brand of Vardhman Hydraulic Hoses Pvt. Ltd. in Bhiwadi, Rajasthan, makes its sand blast hose to exceed IS 5894. It has an extra-thick seamless rubber lining free from mineral filler, high-tenacity synthetic yarn braid reinforcement, and a cover resistant to abrasion, ozone and weather. Its DIN abrasion loss is below 60 mm³. Working pressure is 175 PSI / 12 BAR and burst pressure 700 PSI / 48 BAR, across bores from 1/2" to 2" (12 to 50 mm), for service from -40 C to +75 C, in 40 m standard coils. The reinforcement includes a copper element that reduces static build-up.

The bore should suit the nozzle, as the compressor and nozzle guide above explains. The full size table is on our sand blasting hose specification page.

Setting up a blast line? Start with the hose

Tell us the nozzle size, the abrasive and the length of run, and we will recommend the bore and send a quote.