From Silica To Cullet

Powdered glass cullet is made from ground recycled glass, which begins life as virgin glass, a product made primarily from silica sand with certain additives combined with it to lower the melting point and increase chemical resistance. There are a variety of types of glass available on the market, but the most common glass in circulation today, and the type most often found in glass cullet form, is soda-lime glass. This type of glass contains between 70 to 74 percent silica, and is the glass from which most all bottles and jars are made.

Soda lime glass is made by preparing a batch of raw materials including silica, lime, soda, alumina, and iron oxide if the glass is to be green or amber according to a predetermined formula, and melting the mixture at very high temperatures, usually in gas fired furnaces. The relative quantities of the various raw materials differ according to the intended use for the glass. There are two main type of soda lime glass, the first of which is known as float glass, which is formed by a float process into sheets of glass, and the second of which is known as container glass, which is blown and pressed into the desired container shape. Container glass makes up the bulk of glass cullet, as most glass cullet comes from bottles and jars deposited at recycling stations, or put out for collection at kerbside pickup points.

Once the glass mixture is melted down, it is then stirred thoroughly. It is important in order for the glass to have a uniform strength and composition that the melted glass is homogeneous. After the homogenization process is complete, the glass mixture is then refined to remove unwanted bubbles which could cause structural defects and manufacturing faults later on. Sodium sulfate and sodium chloride are both fining agents added to the mixture that aid in the removal of unwanted gas bubbles.

The glass is then formed into plates or containers, and goes out into the world where it performs its function, and is subsequently returned for recycling, usually shattered into many pieces and mixed in with other glasses, plastics, and other contaminants.

This is raw glass cullet, and in order to be transformed into useful, clean, powdered glass cullet it must undergo benefication, a process whereby the contaminants are carefully removed using a combination of magnets, metal detectors, washes, human picking stations, and a process known as fine sizing.

Fine sizing is a process whereby the glass cullet is gradually ground down into finer and finer particles, and passed through a series of increasingly fine screens. As this process is taking place, ceramics and other harder compounds are not worn down as quickly as the glass, and so are left behind on the screens. The resulting product is clean, contaminant free, fine powdered glass cullet, ready to be used in a wide range of applications.

Powdered Cullet Applications

Filtration Systems

For many years, water filtration systems made use of silica sand as a filtration agent, but it has since been discovered that powdered glass cullet can be even more effective than silica sand, and is sometimes less expensive to obtain. The main advantage of powdered glass cullet over silica sand, cost aside, is the fact that glass cullet does not allow harmful bacteria and deposits to adhere to the powdered particles, which means that the resulting water is cleaner, the overall life of the filtration system is longer, and the sand does not need to be replaced nearly as often.

Septic Treatment Systems

Because powdered glass does not retain microbes and bacteria the way natural sand does, powdered glass is also being used in some septic filtration applications. The structure and nature of powdered glass cullet is perfectly suited to filtering out impurities from septic sources, far better than more traditional mediums.

Filler Aggregate In Concrete

Powdered glass has proved to be a useful filler aggregate in concrete applications. The pozzolanic nature of glass (a term which describes its reaction with lime which results in strengthened compounds) makes for a stronger aggregate, and the powdered form of the glass makes for nice dense particle packing. When powdered glass cullet is used as an aggregate, less drying shrinkage is observed, and there is also increased elasticity. Powdered glass cullet makes a highly resistant and strong aggregate, it is not temperature sensitive, and has very good freeze/thaw resistance not to mention excellent resistance to abrasion.

Fluxing Agent

Powdered glass cullet makes an excellent fluxing agent for a wide range of applications. When used as a fluxing agent in brick manufacturing, the firing temperature of the bricks can be reduced by a hundred degrees. This sort of temperature reduction represents significant savings in energy and production costs, not to mention wear and tear on the ovens. Powdered glass has also been found to be an effective fluxing agent in the ceramics industry, and in the metal industry.

Blasting Abrasives

Powdered glass is highly abrasive, and is starting to replace traditional blasting media as the preferred choice. Sand blasting is a common method for removal of paints, lichens and other substances from walls, floors, and other surfaces, and at one time silica sand was the media of choice for this application. Powdered glass has several advantages over silica sand however, for starters it is denser than many other types of blasting abrasive, and provides far more particles per pound. This means faster and better cleaning. Another major advantage of powdered glass cullet is the fact that it contains hardly any (less than one percent) crystalline silica, a compound which causes a serious lung disease in humans, and which is prevalent in silica sand.

Ceramics

As was briefly mentioned above, powdered glass can function as a fluxing agent in the production of ceramic items. Powdered glass also has other applications in the ceramic world, as an additive and as a means of ornamentation. Powdered glass is often combined with ceramics to create lightweight ceramics, or can also be sprinkled, or combined with a gloss to provide a shiny or sparkly finish on some ceramic items.

Purchasing Powdered Glass Cullet

Powdered glass can be one of the ’safest’ forms of glass cullet to purchase as the fine sizing process removes a great deal of the contaminants that larger forms of glass cullet may possibly still contain. However, not all powdered glass has been fine sized, in many cases it may simply have been ground down from raw cullet, and if this is the case, it may still contain contaminants. Whilst one of the most versatile and potentially cleanest forms of glass cullet, powdered glass cullet is only as good as the benefication process it underwent before being ground into a fine powder.

A rule of thumb when investigating powdered glass cullet is to inquire as to the methods of benefication that were employed during recycling, and to obtain a sample of the product, and perhaps even references from other customers before committing to a larger purchase. Whilst this might sound overly picky, powdered glass containing contaminants, especially ceramic contaminants, may lack necessary strength, chemical resistance, or react badly with other materials.

Powdered Glass Cullet Supplier

Please contact us through the form below and let us know your specific requirements. We will usually get back to you with a price quote within a few hours.

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Of course, the problem that many artisans and glass manufacturers face is obtaining [post consumer glass cullet that is the right color for their intended operation. In the past it has been simpler to simply obtain new glass products, but a rising environmental consciousness, and a desire to economize on material costs has sent many people back to looking at glass cullet as a raw material for their products.

Post consumer glass cullet generally comes in one of three color grades, amber, green, and clear. It is sometimes possible to obtain presorted glass cullet in which the glass ordered is of a uniform color, but it is still cheaper to obtain mixed color glass cullet and separate it ones self. This may not be a viable option for large scale commercial operations, but for craftspeople and smaller operations, it may be worth the saving in cost to take a little extra time to sort the cullet oneself. Mixed cullet generally originates from kerbside pickups, where different types of glass are tossed in together with other materials intended for recycling, such as papers and plastics, and the breakages and ensuing mixing of the various colors during transport results in the various shades of cullet being mixed together.

Once one has obtained either amber or green cullet, the problem then becomes obtaining the right sort of color for the specific application that one intends to use it for, not to mention the desired opacity. Most craftspeople and manufacturers of decorative products do not wish to restrict their products to being clear, brown, or green. In order to make visually appealing products, the glass cullet must be decolorized before the artisan or manufacturer adds their own colors to it.

Decolorizing Glass Cullet

This article supposes a basic level of competence and knowledge with regards to the handling and melting of glass cullet, and is by no means a complete guide. The information below simply provides a basic outline as to how the decolorization of post consumer glass cullet can be achieved.

Post consumer glass cullet can be decolorized in a variety of ways, and each type of glass cullet decolorizes differently.

Decolorizing Brown/Amber Glass

If zinc oxide is added to amber glass, the amber/brown color is lost and one is left with glass that retains a blue or green coloration. This is quite pretty, but if one would like to make the glass entirely clear, then erbium oxide and manganese oxide can be added to clear the color from the melt.

Decolorizing Green Glass

Green glass requires two stages to decolorize. Firstly, the melt must be oxidized, which changes the deep green color that most green glass cullet has into a more yellowish green color. Manganese Oxide can then be added to create a glass that is not clear, but is merely a grey color. From this base color, different agents can be added to create a wide range of varying colors.

Coloring Glass

Once the glass has been decolorised, there are a wide range of options available for recolorizing the melted glass. There are a wide range of commercial blended colorants available on the market, and these have been developed to the extent that making one’s own colorants is largely unnecessary. For those who like to experiment however, some common colorants and treatments include:

• Cobalt Carbonate
• Borax
• Zinc Oxide
• Manganese Dioxide
• Potassium Permagnate
• Erbium Oxide
• Neodymium Oxide
• Cerium Dioxide
• Titanium Dioxide

These can be blended in varying quantities to produce various results. Other factors which will affect the color of glass are the temperature of the melt, the atmosphere of the melt (whether it is neutral or oxidized), and the blends of glass cullet used in the melt if one begins by using mixed colored cullet, or uses varying proportions of differently colored cullet.

It is highly recommended that decolorization and colorization of glass cullet only be undertaken by those with sufficient training, as some of the chemicals are quite dangerous if handled incorrectly, and indeed, the processes involved in successfully working with glass are inordinately delicate.

Post Consumer Cullet

The ability to work with multiple colors of glass cullet, and to blend and work the material into new colors and forms is not merely an aesthetic undertaking. Whilst many craftspeople and manufacturers make beautiful products from post consumer cullet, there are also very real environmental benefits to taking post consumer glass cullet and recycling it into new products. It has been reported that merely recycling one glass bottle saves enough energy to power a light bulb for an hour, and yet much glass produced across the globe today is not recycled, but ends up in landfills, where it will remain for millenia. Those manufacturers and artisans who choose to use post consumer glass cullet as a raw material for their art and products are not just saving themselves some money, they are also helping to save the planet.

Using post consumer glass cullet beautifies the world twice, once when the earth’s resources are spared from making yet another unnecessary glass bottle, and for a second time when the decorative or artistic recycled product is made.

Glass cullet prices

We supply glass cullet from all over the world. Please contact us through the form below and let us know your specific requirements. We will get back to you with price quotation shortly.

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As with most forms of recycling, a major problem for glass cullet recyclers is contamination. Glass cullet is often contaminated with metals, ceramics, pyrex, general rubbish, and sometimes even syringes and medical waste. There are a variety of methods used to clean up glass cullet, and the most popular of these is outlined below.

The glass cullet is fed into a hopper which feeds it onto a conveyor belt. The glass cullet then travels along the conveyor belt, where magnets remove metals such as bottle caps, and other contaminants that have made their way into the cullet. The cullet then passes under a metal detector which removes any remaining pieces of glass cullet contaminated with metal. This process can be repeated several times until all the metals have been removed from the cullet.

Metals are not the only contaminants that can cause problems in glass cullet however, ceramics, plastics, and other rubbish can often infiltrate the cullet. These are usually picked out by hand by workers at picking stations, or by automated systems.

An automated method of removing ceramic contaminants in glass cullet recycling is known as “fine sizing” and essentially involves grinding and/or pulverizing the glass cullet. In either case, the glass cullet breaks down more easily than ceramic contaminants, and as the glass cullet becomes smaller and smaller, it is passed through a series of screens, leaving behind the more resilient ceramic contaminants, which can cause structural defects in the resulting glass products if not removed before the cullet is melted down and formed into new glass items, or sold to be crushed or powdered for inclusion in other materials, or to be used in other applications.

Glass Cullet Supplier

We supply all types of glass cullet. Please contact us through this form below and let us know your specific requirements. We will get back to you within a few hours

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