Media blasting is the process of blasting with abrasive media which was more commonly (and more correctly) called sand blasting. Back in the early days of blasting, the predominant abrasive of choice was sand. Silica sand is the more appropriate name \u2013 based on the fact that common sand is primarily comprised of mineral quartz, which itself is composed of silica, and oxygen. Silica sand was used because it\u2019s cheap, readily available, and effective for many applications. These were simpler times when cost and results were given more weight than the health and safety of those exposed to it. Seat belts, for instance, weren\u2019t required in cars and trucks. Cigarettes weren\u2019t considered dangerous. <\/p>\n\n\n\n
We now know that breathing silica dust is extremely dangerous. Silica sandblasting has long been closely associated with the disease historically referred to as miner\u2019s phthisis, potter\u2019s rot, or grinder’s\u00ad asthma. Breathing \u201cdust\u201d in mining and other dust-producing activities has been associated with lung disease since ancient Greek and Roman times. More recently, with the industrial age, came inventions such as the pneumatic drill and jackhammer for boring into rock, (circa 1897), and sand blasting for finishing hard surfaces like iron and steel (circa 1904). These innovations produced large amounts of silica dust with little care, or understanding, for the health concerns they created. More accurately called silicosis, this deadly disease is caused by the inhalation of crystalline silica.<\/p>\n\n\n\n
When considering abrasives, there are four very important physical characteristics that help to understand their use and application; 1) hardness, 2) shape, 3) friability, and 4) density. The first of these, hardness, is easily understood. We\u2019re talking about mineral hardness. In this case, imagine the diamond scratching glass example that we\u2019ve all seen demonstrated in one way or another. The diamond is min\u00aderally harder than the glass, when the edge of the diamond is scraped across the glass, it scratches. The explanation \u2013 diamond is harder than glass. When used as blast abrasives, harder materials are generally more \u201caggressive\u201d than softer material.<\/p>\n\n\n\n
Let\u2019s examine some of today\u2019s more popular blast media choices with these characteristics in mind as well as their effect on different applications. When you shift away from sand as a do-it-\u00adall blast medium, most people attempt to replace this dirt-cheap blast abrasive with something that offers increased value for the increase in cost. In other words, if you\u2019re going to pay more for something, you look for a better, quicker, or more efficient medium for the additional money.<\/p>\n\n\n\n
These abrasive blast particles have a knife-like shape that strips everything from light paint to heavy soot with relative ease. The density of baking soda is light, so much of it\u2019s power comes from aggressive shape. The fact that baking soda abrasive is so non-damaging to substrates is due to its softness, and its friability. This blast abrasive pays back its higher price by offering several distinct benefits. It\u2019s non-destructive to most materials including wood framing, and other building materials. Again, it\u2019s friable and soft so it has virtually no impact on surfaces like steel, and glass. Here\u2019s the real hidden benefit \u00adwhen blasted, the chemical side of baking soda also neutralizes odors from smoke and fire as well as mold, sewage, guano, drugs, and other smelly contaminants. This effect is multiplied by the friability factor \u2013 when media particles break easily, they create dust. Often wrongly seen as a negative, baking soda dust in contact with odor sources, means more effective odor reduction.<\/p>\n\n\n\n
Click here for Baking Soda media<\/a><\/p>\n\n\n\n Dry ice is one of the most misunderstood blast media, but it can be examined in a similar fashion. Dry ice is solid carbon dioxide. As such it is \u201cminerally soft\u201d, and non-damaging to most hard surfaces like stainless steel, and other metals. The shape of most dry ice particles is rather \u201cblocky\u201d due to the particles being comprised of 1.5 mm diameter pellets. So, while not overly dense, it can still be somewhat aggressive against many coatings, and layers of debris. Blasting of industrial equipment and production lines are prime examples of where dry ice really shines is in the area of friability. Upon striking a hard surface, dry ice is smashed into such tiny pieces that the increased surface area of those particles can no longer remain solid at room temperature. They immediately sublimate (turning from a solid to a gas with no liquid state) and \u201cdisappear\u201d into the surrounding atmosphere. Most often, this is highly advantageous, with the blasting process leaving no secondary waste \u2013 no spent medium. This leaves only primary waste \u2013 the dirt or coating \u2013 to be cleaned up and disposed of. One interesting note with dry ice is its extremely cold temperature when solid: -109\u00b0F below zero. This is both a positive and a negative when using this blast medium.<\/p>\n\n\n\n Click here for Dry Ice media<\/a><\/p>\n\n\n\n Walnut shell \u2013 and it\u2019s agricultural cousin corn cob meal \u2013 are two of the more popular and affordable media classified as \u201cblocky\u201d. These two blast media are very similar in nature. Corn cob meal \u2013 the hard inner portion of the corncob \u2013 and walnut shell are both byproducts of their respective primary produce. As such, they\u2019re inexpensive and generally available, with some variation due to seasonal and harvest outcomes. Their lack of friability might lead you to expect that they\u2019re very aggressive against substrates. This is not entirely true, however, due to their very low density and mineral \u201csoftness\u201d they remain nearly non-damaging. In fact, this lack of friability is one of the distinct advantages to these media \u2013 low dust levels from blasting. Their low cost, ability to effectively strip coatings, and their safe nature make them prime candidates for many large blasting jobs such warehouse fires that require quantities of one-pass blasting media. Please note that walnut shells are a tree nut. Operators should be screened for tree nut allergies before any exposure to walnut shells. When necessary, use corn cob meal as your primary choice and avoid the risk of an allergic reaction, which in some cases may be severe.<\/p>\n\n\n\n Click here for Walnut and Corn Cob blasting media<\/a><\/p>\n\n\n\n First, let\u2019s confront the fact that glass is primarily made from silica sand! This is where an understanding of organic chemistry (science) and physical properties of matter (engineering) would be helpful. We\u2019ll just agree that while glass is made from silica, it\u2019s not silica anymore. The basic mineral quartz has undergone a phase change and is no longer the crystalline structure that causes respiratory diseases like silicosis. <\/p>\n\n\n\n Adequate safety measures (respirators, ventilation, gloves, etc\u2026) should still be taken, but the basic premise is that you\u2019re protecting yourself from particulate that is a nuisance, not a killer. Crushed glass is sourced from recycled bottle glass and is readily available \u2013 thus a very inexpensive option as a blast abrasive. Crushed glass is angular in shape, and thus aggressive against coatings, and profiles (roughens) hard surfaces \u2013 beneficial when painting or powder-coating is necessary. Due to its low cost and ready availability, crushed glass is very popular when used in processes that only allow for one pass of the media through the system like wet abrasive blasting. Glass beads, on the other hand, are created by melting glass cullet, and spraying the molten glass and collecting the resulting droplets, or beads. This is a relatively expensive process, and glass beads are usually three to four times more expensive than crushed glass. Invaluable for applying a smooth, matte finish to stainless steel and aluminum, glass bead is a natural choice due primarily to it\u2019s round shape.<\/p>\n\n\n\nDry Ice media blasting<\/h2>\n\n\n\n
Walnut Shell and Corn Cob blasting<\/h2>\n\n\n\n
Glass media blasting<\/h2>\n\n\n\n