Pumice has a number of characteristics that combine to make it a valuable and versatile player in a variety of industrial processes and products.
Pumice is amorphous and generally inert, has a neutral pH, yet is hard enough to be used as an abrasive. Yet, because of its porous nature, pumice is amazingly lightweight.
The friable nature of pumice is one of its most significant characteristics—meaning pumice is easily crushed and refined without loosing its utility: at any grade—from half-inch aggregate to microfine powder—pumice remains abrasive, absorbent, non-compacting, lightweight.
Sustainable and abundant, pumice is indispensable.
Grouped by attribute, the following is a breakdown of where and how pumice is used.
Horticultural Applications for Pumice
Pumice is renowned for its ability to condition soils and growing mediums by adding critical properties to the soil, such as enhanced drainage, and the ability to hold both water and air. Not only can plant roots easily access moisture and oxygen through pumice-enhanced soils, but the carbon dioxide respirated by the roots is able to easily escape the root zone.
—Soil Conditioner for Potting and Garden Soils: Lightweight and friable, pumice will not compact or become soggy, increases the bulk density of potting mixes and loosens the density of heavy clay garden soils, enhances drainage and aeration, holds onto vital nutrients to regulate fertilizer applications, reduces crusting, cracking, flooding and shrink-swelling, does not attract or host nematodes or insects, is pH neutral, and will not rot or decompose.
—Lawn and Turf Management: Pumice is used both to create a quality seed bed for new turf and as a topping treatment on heavily trafficked turf areas to (in combination with aeration) combat compaction problems.
—Landscaping Mulches: Pumice is decorative and effective in controlling weeds and retaining moisture. The lightweight nature of pumice mulches doesn’t compact the soil, nor will pumice rot away.
—Roof Gardens: Consider the things that matter when it comes to soil ideal for growing…the proper pH (pumice is pH neutral), moisture retention, root respiration, nutrient retention, resistance to compaction, good drainage. Pumice improves soils in all the above areas, but shines in an area of critical importance to roof top garden engineering…replacing part of the soil with pumice significantly reduces the weight load.
—Packing and Storage Medium: for storing tubers, roots and bulbs.
—Propagation Medium: Unlike heavier, more compact sand media, lightweight pumice media gently releases the roots when cuttings are removed.
—Growing Medium for Hydroponic Applications: Several pumice properties make it a great choice for hydroponics—non-compacting, lightweight, porous, pH neutral, permanent, reusable, inexpensive, available in various grades (particle sizes) so as to allow the grower to manipulate drainage capacity.
—Seed Coatings: Absorbent pumice powder is used as a seed coating to protect ag crops. Pumice is also used for pelleted seed formulations developed for precision seed drills, especially for irregular shaped or very small seeds, as pelletized seeds flow smoothly and predictably through the drill.
Pumice for Filtration
Pumice is a viable alternative to sand and anthracite as a filtration and clarification media for several reasons:
1)Pumice has a low-density, multi-faceted, angular structure that traps and hold impurities;
2)is chemically inert, inorganic, long filtration media lifespan;��
3)versatility allows for use in single or multi-media filters and in both pressure and rapid-gravity filter designs;
4)low-cost filter refurbishment;
—Waste Water Treatment: Used both in large industrial applications like treatment plants and in small point-of-use treatment cartridges.
—Drinking Water: The multi-faceted structure and inert purity of pumice makes it ideal to capture and hold impurities.
—Pumice Soil: Adding pumice to soils can enhance drainage and oxygenation for better crop management.
—Reverse Osmosis Processes: Pumice filtration media serves as an excellent pre-treatment layer in reverse osmosis and desalination processes.
—Biomass Support for Aerobic Treatment Process: Pumice provides a porous, concentrated biomass for growing the non-air breathing microbes that digest or destroy organic pollutants.
—Sludge De-watering: Adding pumice to sewage and industrial sludge prior to the final de-watering step improves both the process and quality of the outcome.
—Beverages: Purification of the ingredients and/or the finished beverage by filtration is essential to flavor consistency and quality. Pumice has the crucial filtration media characteristics demanded by such an exacting filtration process.
—Textile Softening: Known as stone-washing, pumice stones are tumbled with stiff fabrics or assembled garments (like denim) to soften the feel and age the appearance. Pumice stones are not only highly effective at giving fabric a natural worn-in look and feel, but pumice stones are long lasting and gentle on the expensive tumbling machinery. As for environmental friendliness…a natural pumice beats chemical and enzyme baths hands-down.
Industrial Abrasive Pumice
Pumice is widely used as an industrial abrasive where the protection of the surface is critical. Various grades and blended grades of pumice are used to: Polish glass, clean and texturize electronic circuit boards, clean lithographic plates, prepare metal surfaces for electroplating, buff leather and fine furniture woods, act as a tumbling media for things like buttons, cutlery, small metal or plastic parts.
Product Abrasive Pumice
The mild abrasive quality, benign chemical nature, and ability to refine pumice to fine dust make it an ideal additive for cleaning, polishing, and exfoliating products. Pumice powder is found in:
—Dental Prophy Pastes: Cleans and polishes while protecting delicate tooth enamel. Also used to prepare teeth for resin bonding applications.
—Cosmetic Scrubs; Exfoliants: Gently removes dead skin while cleaning, smoothing and improving skin texture.
—Rubbing Compounds: Delicate finishes require a delicate abrasive to gently remove waxes, paint defects, oxidation, and scratches.
—Scouring Pastes and Powders: Used to clean and polish, removing grease, dirt, soap scum, mineral deposits, scuffs, scale without harsh chemicals.
—Pencil Erasers: Pumice aids in separating the graphite from the paper fibers so it can be captured by the rubber compound.
—Callus Removal Stones: Can be either cut natural pumice stones or formed and pressed from pumice aggregate.
—Stain Removal Stones: Sticks cut from natural pumice blocks or pressed and formed from pumice aggregate.
Pumice concrete is composed of Portland Cement, pumice aggregate, pumice sand, pumice pozzolan, and water. Compared to regular concrete, pumice concrete offers roughly a one-third reduction in weight. Proportioning, mixing and placing are done in a similar manner to that of conventional concrete, as is the finishing. The applications for pumice concrete are also the same as those of standard sand-and-gravel concrete, but is particularly useful where lightweight concrete is desirable.
Concrete and Masonry products often make up a large part of a construction project, especially those requiring strength and longevity. One of the biggest drawbacks to these enduring concrete structures is their bulk and weight. That’s where lightweight pumice really shines. For example, a standard concrete building block, using common sand and gravel aggregate, creates efficiency issues—both in terms of labor costs and sizing the supporting structures, such as footings for the deadweight load. But when blocks are made with lightweight pumice aggregate, sufficient compressive strength is retained as the weight goes down. At the same time, thermal conductivity goes down, as does acoustical transfer…all because of the natural structure of pumice. Pumice concrete benefits include:
—Lightweight pumice concrete ishighly elastic, providing more flexural strength than standard concrete, affording enhanced resistance to wind forces and seismic shock waves while providing excellent compressive strength.
—Lightweight pumice concretereduces deadloadrequirements (and job costs) for structures. Pumice concrete can be handled by lighter equipment. Another key factor is the cured concrete’s workability, particularly in sawing, drilling or nailing.
—Pumice aggregate provides up to4x the insulation valueof standard aggregates or a standard concrete mix, is freeze-and-thaw cycle resistant, and eliminates or reduces moisture condensation on structure walls and ceilings, making it an excellent choice for colder climates and locations that experience dramatic changes in weather.
—Thefire resistanceof lightweight pumice concrete is also a big benefit: the same hour-ratings can be achieved using less pumice concrete than what is required with standard concrete.
—Manufactured Stone Veneers: Another industry where pumice concrete is an ideal fit is the booming manufactured stone and brick veneers industry. The beauty of a fieldstone wall, for example, is attained at no additional cost in base support or over-sized footings. Pumice concrete-based manufactured stones are cheaper to ship, less time-consuming and labor-intensive to install, are assembled using standard mortar mixtures, yet perform and endure like any other masonry products, only better.