How Abrasive Blasting with Baking Soda Works
Using sodium carbonates as cleaning agents goes back to ancient times, although soda blasting did not come into use until three decades ago. That is when engineers working on the 100th-anniversary restoration of the Statue of Liberty contacted Church & Dwight Co., Inc., maker of Arm & Hammer products, hoping to find a way to remove the final two layers of interior coal tar coatings without damaging the statue’s delicate copper skin.
Trial and error with many different blasting abrasives led to the discovery that sodium bicarbonate could do the trick exceptionally well and without causing any surface damage. One hundred tons of baking soda were used to clean Lady Liberty, and as a follow-up to this success, the manufacturer launched the first sodium bicarbonate blasting abrasive, ARMEX.
How Baking Soda Blasting Works
Baking soda blasting can be done wet or dry. Both methods require compressed air or water to deliver the media.
A soft crystal (Moh’s hardness of 2.5), baking soda is harder than the contaminants to be scraped off — such as grease, oil, paint and environmental soil — but softer than the substrate. This is how it is able to clean without damaging the underlying surface.
By comparison, when a hard-abrasive particle impacts a substrate, the energy of the impact is transferred into the substrate, fracturing it and blowing off materials. When baking soda impacts a substrate, the impact energy is transferred back into the baking soda crystal itself, which gets fractured and blown apart. The substrate remains unchanged.
Vapor blasting with ARMEX
Choosing a Formula
The blast media used in soda blasting can be formed from several different sizes of sodium bicarbonate crystals, each appropriate for specific types of cleaning applications. Generally speaking, more robust surfaces can withstand higher crystal sizes. Larger particles yield more cleaning power, making the correspondent formulas appropriate for thicker coating removal and heavier cleaning applications. Medium-sized particles carry less mass but deliver more hits per square inch to the material being cleaned and are thus suited to removing thinner coatings on more sensitive substrates. Smaller particles are best for substrates that are more delicate.
The team at ARMEX uses these different particle sizes to create specialty sodium bicarbonate formulas for specific surface preparation requirements. They have developed 12 such formulas, with mean particle sizes ranging from 70 microns to 270 microns.
Before (left) and after (right) paint removal
Soda blasting is a versatile process — from its use in cleaning colossal statues to blasting greasy residue off automotive parts to removing paint and contamination when non-destructive cleaning is a requirement. It can be used on a wide variety of materials, including glass, steel, aluminum, lead, alloys, plastics, rubber, composites, wood, masonry and PVC, all without damaging the substrates.
Baking soda is a natural desiccant and loves to absorb water, but ARMEX includes flow aids and advanced moisture-control additives that prevent blasting equipment from clogging and help to preserve the product when stored or used in high moisture environments. See how this makes a difference:
About the Abrasive
Baking soda is environmentally friendly and classified as a non-hazardous and non-toxic (GRAS) material. It is water soluble, pH neutral, non-flammable (won’t thermal spark) and silica free. ARMEX is also the only baking soda abrasive on the market that is USDA A-1 approved, which means the product holds a USDA certification as a general cleaning agent for all surfaces in all areas that are in contact with food.
*Claims or positions expressed by sponsoring authors do not necessarily reflect the views of TPC, PaintSquare or its editors.