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Posted by Joe Cimoch on Saturday, January 05, 2008 at 19:29:22 :
In Reply to: Soda Blasting posted by Joe Cimoch on Saturday, January 05, 2008 at 18:09:09 :
Probably the first and most asked question about soda blasting would be, “is this the same soda I can buy from the store for my refrigerator”? Well, all baking soda is chemically the same (NAHCO3). However, the larger particles are sieved out for use as a blast media. Most contain uniform particle sizes from 90-260 micron and ingredients to repel moisture that aid in a consistent flow.
The use of baking soda, as an abrasive, has been well known for many years. It is one of the oldest materials used to manually scrub a variety of things throughout the household. It has been widely used as a soap or degreaser. The solubility and the "safety” of soda, around food and people, made it ideal for restaurants. It has been said that the first powdered use was (and still is) to clean teeth at dental offices in the 70’s. Armed with only a tiny water ring and this product, which they blast at 60 PSI, dentists are able to remove stains and debris. However, the enamel on the teeth remains undamaged during the process. Then soda was expanded to micro-blasting circuit boards (dry, of course) in order to clean flux off the boards. Many micro-blast applications are still used today.
The old timers will tell you that soda was first exposed as an excellent abrasive during the rebuilding of The Statue of Liberty for the Centennial (finished 1986). It was the first large scale use of soda as a blasting abrasive. It proved to be the ideal medium for use inside The Statue to remove coal tar, paint and corrosion. Many minds tried every way imaginable to remove the coatings and all failed, until baking soda was tried. It worked! Next came a full scale “assault” on finding things to blast clean. This paved the way for the beginning of the complete soft abrasive industry; which also includes materials like sponge and kieserite.
Soda is not an alternative to a general purpose blast abrasive. It is more costly to manufacture. Therefore, more expensive for the end user, and its soft nature simply will not achieve the kind of production rates that an abrasive like Garnet can render. Still, soda is widely used in specific areas, and on specific substrates, and for a number of different reasons. Some of the important characteristics that make soda unique in the world of soft abrasives are as follows:
1. Soft abrasive (does not harm glass, ceramic, metal, etc).
2. Friable (breaks down on contact).
3. Non-Sparking.
4. Water soluble.
5. Food Grade.
6. Well known chemistry (mostly benign).
7. Recognized as safe to use almost anywhere.
For example, during fire restoration projects, soda is used because it will effectively remove ash and soot from a sensitive substrate, like wood or brick, without damaging the surface. In addition, it also has the ability to neutralize most of the burn smell associated with structural fires. Most of the soot infected materials, before soda blasting, would have had to be taken out and replaced which is time consuming and expensive. In auto body restoration, soda is able to remove several coats of paint from both metal and fiberglass body cars without any damage, while leaving a nice smooth finish. The higher a pH soda has will cause it to act as a natural rust inhibitor. Which in some cases, will hold for months without any sign of rust. Another plus in auto body restoration is the soft nature of soda. You are able to brush by glass, chrome bumpers and sometimes even plastic moldings in most cases with little to no damage. This saves a great deal of time by eliminating the need to completely disassemble a project car. Another common application for soda is Graffiti removal. Again the soft soda is able to remove paint from brick or natural stone without damaging the underlying material. A big plus with graffiti is that after a soda blast you are able to, in most cases, just simply rinse the soda away because it is easily soluble.
However, a trait that is desirable in one application can be undesirable in another. When soda is used in applications near vegetation, great care must be taken to keep the product contained. The high pH of soda can cause browning or sometimes even death to flowers, shrubs and trees. That is why soda can be chosen for just one or all of its special unique traits.
The most popular application method of soda blasting is “dry”. This is the preferred method for auto body restoration. If one is considering “dry” soda blasting as a business, in order to do it right, be sure to keep in mind the initial cost can be tough. You will need a large 185 CFM compressor or bigger and not just any old sand blasting hopper. Soda blast pots are unique. They must be capable of metering the abrasive flow rate down to a minimal amount to keep cost down, and also it’s good to be able to adjust the pot pressure separate from the blast pressure to ensure a proper consistent flow. Most sand blast hoppers are unable to…or not designed to do this. At the same time, the hot compressed air from the compressor will produce moisture and must be cooled and run through a moisture separator. This is necessary because soda is a water soluble abrasive. Soda will soak up moisture, when it does it will become sticky when wet and will build up inside of your machine’s working components and hoses. When it dries, it can become very hard and soda blasting without a moisture separator can have a blast pot shut down several times in one day. This of course, can be extremely costly and time consuming.
This additional startup cost is unique to soft, soluble abrasives. For the entrepreneur who does not have the cash up front for a system like this, do not be afraid. Almost every manufacture of this kind of equipment is able to provide or point you to a lease or finance program. If you are looking to soda blast just a few projects a year, it would not be wise to go out and buy a complete set up. It takes time and experience to complete a quality soda blast project. In this case, it is best to pay an experienced professional.
Another great way to utilize the unique traits of soda blasting is in the “wet” application. This is a piece of equipment anyone can afford, and most will work with almost any standard pressure washer. Introducing soda into a stream of high pressure water also has its advantages. The water is able to aid in the cleaning by getting into places the dry abrasive is unable to penetrate. Also with this method, there is absolutely no dust, which can be a huge problem in the dry application. The wet method is the preferred technique for a job like graffiti removal. The down side is that the wet application, in most cases, is much slower than the dry.
One might wonder what the future holds for soda or what soda holds for the future. No one knows what the future of soda blasting holds. This industry is growing by leaps and bounds, with no end in sight. As new and inventive ways to blast are imagined, new substrates are now being tested every day. However, I truly believe the best is yet to come. What are you thinking of soda blasting today?
By Gary Birdwell - Universal Minerals, Inc.
Article published in Cleaner Times Magazine (April 2007)
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