What is abrasive blasting or Sandblasting, as it is more commonly called? The short answer is: Propelling a stream of “media,” under high pressure, at a surface, through a nozzle. However, there is more to it than that.
First off it has many aliases: Sandblasting, Bead Blasting, Shot Blasting, and more. While each of these actually refers to a specific media being used, most people use these terms in a universal sense.
Since Sandblasting and Abrasive Blasting are general terms, let’s explore some of the many diverse aspects. There is dry abrasive blasting and wet abrasive blasting. Here we are talking about dry abrasive blasting. This process (sandblasting) is selected for three different end results. The first and most common is to remove an unwanted coating from the surface of a substrate. Ex: Paint, rust, grease, corrosion, and dirt. Just to name a few.
Two other desired outcomes are making a smooth surface rough, and making a rough surface smooth. Of course this depends on the media chosen.
Why would you want to make a smooth surface rough, you might ask. That is a very good question. In the event you would like to re-coat a surface, it can be of great benefit to have it be rough. Not rough as in large gouges or poc marks. In this instance you would want a small profile depth to the roughness. This rough surface gives the coating something to hold onto.
For example, if you spray paint on a piece of glass, even after the paint has cured it will easily scrape off the surface. However, if you paint a piece of metal, for example, that has a minute rough surface, it would be very difficult to crape the paint off. After curing the paint holds tight to the little hills and valleys in the rough metal surface.
The one major separating factor, to the outcome of the blasting process, is the choice of media used. There seems to be an unlimited number of media choices. Such as:
Sand – Metal grit – Glass beads – Crushed glass – Shot – Aluminum oxide – Silicon carbide – Walnut hulls – Coconut shells – Plastic – Corn cob – Baking soda – Ceramic grit – Copper slag
This is just a small list of the available media. Each of them have their pros and cons.
When selecting media there a number of factors to consider. Sand, for instance, although being the most well known, has many un-redeeming qualities. To start off with some sands can have a high silica content in them. If not properly protected from this silica dust, workers, or bystanders for that matter, can develop silicosis, lung cancer, and breathing problems. Sand can also have a high moisture and contaminant content. These two factors can cause major issues with the equipment, including blockages and premature equipment failure. But probably the biggest downside to sand is the fact that other medias can do a better job without the health concerns.
Each job requires careful selection of the correct media for the desired results. Soda cleaning, for instance, can be used on very delicate substrates, like glass and thin metal, without etching or warping.
Abrasives each have a different defining number on the Mohs’ scale of hardness. Selecting the correct media can make the difference between cleaning, not cleaning, or damaging the underlying surface.
In the past abrasive blasting has been considered too dirty, too hard on surfaces and too low tech to be considered for many projects. With the advancement in technology, equipment, and choices of media, abrasive blasting (sandblasting) has become the go-to choice for residential and commercial applications alike.
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