Frequently Asked Questions
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Table of Contents
Basic of Glass Cullet
How is glass produced?
In a nutshell, sand (silica), soda ash (sodium carbonate), limestone (calcium carbonate), and glass cullet are fed into a furnace (around 1500°C hot) in a slow and controlled manner. Once this mixture is in a molten state, it is either poured into molds to make containers, bottles, and glasses or poured into a float bath (containing molten tin) to make it into flat sheets of glass. Depending on the glass product being created, the process will vary slightly. For oven-proof borosilicate glass, boron oxide is added to the molten mixture. Alternatively, lead oxide added to the molten mixture results in a finer crystal glass. In the case of float glass, the glass is annealed, which means it is treated to ensure that there are no internal stresses in the glass. This makes it easier to cut and shape accordingly. After an inspection process, glass is then cut to order using diamond-edged blades, and finally, it is shipped.
What are the different types of glass?
Float Glass - Float glass is made by pouring molten glass on a float bath of molten tin to make it into uniform, flat sheets of glass. These are usually created for large window panes as well as glass facades on buildings.
Toughened Glass - Toughened glass is made to shatter on impact, instead of cracking or breaking into shards which can cause more damage to people around. It is seen in glass shelves, tables, doors, shower doors, glass partitions, etc.
Laminated Glass - Laminated glass is made in such a way that it remains intact if there is any impact or trauma on the surface. This makes it very useful for burglar-proof glass in shop windows and bulletproof glass.
Patterned Glass - Patterned glass is made by passing heated glass through rollers that have some pattern on them. These are used for bathroom windows, cabinets, cupboards, etc.
Mirrored Glass - Mirrored glass or mirrors are made by applying a metal coating to one side of the glass. These are then cut in almost all sizes, ranging from small pocket mirrors to full-length mirrors for bedrooms and bathrooms.
Tinted Glass - Tinted glass usually involves adding metal oxides to give the tinted glass a darker colour. These are designed to block out UV rays and are see-through only from one side. This makes them useful for building windows.
How is glass safer for the environment than plastic?
Since glass is composed entirely of naturally occurring ingredients, namely soda ash, limestone, and sand, it doesn't release any harmful chemicals into the soil. Even when it is not recycled, it does less harm to the environment than plastic does. That being said, it is imperative to try and increase the amount of glass being recycled, to ensure that glass doesn't even make it to the soil or a landfill.
Can glass be recycled?
Yes! Glass is one of the most recyclable materials on planet Earth. It is 100% recyclable and has an unlimited life. It can be recycled endlessly without a loss in its quality or purity.
How is glass recycled?
Glass recycling is the processing of glass scrap into usable products. The steps in the process are:
Glass waste is collected by waste collection units, which provide this waste to cullet suppliers.
Contaminants like paper, plastic, metals, and heat-resistant glass shards which can compromise the melting process have to be removed from the cullet. The cullet is then segregated based on colour.
Glass cullet segregated by colour is supplied to various industries based on their requirements.
Recycled glass manufacturers use the cullet alongside the virgin raw materials in the glass production process. Depending on the needs, they produce different recycled glass products like bottles, containers, float glass, or other varieties of glass.
The recycled glass products are delivered to companies or end-users depending on the products and are back in the consumption stream.
Can glass and plastic be recycled together?
Mixing plastics and other materials with glass scrap makes the recycling process more complicated, as there are more contaminants to remove from the glass waste when it arrives at cullet facilities. If these contaminants are melted with glass, it can cause manufacturing defects.
That is why we at Terraglass do our utmost to ensure that glass cullet is free from contaminants when it reaches our clients.
What can recycled glass be used for?
1. Recycled glass products: Glass bottles, containers, float glass among others.
2. Ceramic sanitary ware production
3. As a flux in brick manufacture
4. As an abrasive
5. As a water filtration medium
6. In the production of astroturf
7. In sustainable architecture projects
What are the benefits of recycling glass?
Glass produced from recycled glass reduces related air pollution by 20% and related water pollution by 50%.
It reduces the amount of waste that is being sent to landfills, which can make landfills slightly safer.
Glass recycling is sustainable, as the glass can be recycled again and again without a loss of quality.
It leads to other savings in raw materials, energy, and as a result, brings down the amount of greenhouse gases being released into the environment.
What is glass cullet?
Glass cullet, also known as glass scrap, is broken or crushed glass that is ready to be re-melted and used in the glass recycling process. There are two types of glass cullet, internal cullet, and external cullet.
Internal cullet consists of glass waste that does not clear quality control checks in glass industries or waste that is rejected due to deformities or cracks.
External cullet refers to the post-consumer glass waste that is collected with the idea of recycling and is recovered from the municipal waste stream.
What are the different uses of glass cullet?
Glass cullet is a versatile material with a variety of uses in different industries. Some of these are:
Recycled Glass Manufacturing - As a substitute or alongside raw materials like Sand (silica, SiO2), Sodium Carbonate (soda ash, Na2CO3), and Limestone (CaCO3).
Civil Engineering - As a cement substitute in roadbeds, pavements, and in the production of self-compacting concrete. Finely ground cullet can be used as a sand substitute or as an alternative for granular materials. It has also been used in highway construction and embankment projects when possible.
Drainage - As a drainage system foundation and a drainage filter/medium.
Stone/Tiling - Used within the tiling and stone industry to give glossy finishes to products like floor tiles, kitchen countertops, glass tiles, etc.
Why is glass cullet used in glass manufacturing?
Glass cullet is used extensively in glass manufacturing as it allows manufacturers to bring down their dependence on virgin raw materials like sand, soda ash, and limestone. Cullet has a lower melting energy requirement which reduces the energy costs, as furnaces can run at lower temperatures. Adding cullet in manufacturing also improves the quality and longevity of glass products.
What are the benefits of using cullet?
Energy savings - Recycling glass using cullet consumes about 40% less energy than using raw materials because cullet melts at a lower temperature.
Raw Material savings - For every 1kg of glass bottles made from cullet,1.2 kgs of raw materials (sand, limestone, and sodium carbonate) are saved.
Reducing greenhouse gas emissions - For every 10% of recycled glass made from cullet, the emission of harmful particles into the atmosphere is reduced by 8%, 10% in the case of sulfur oxides, and 4% for nitrogen oxide. For every 6 metric tons of cullet used in manufacturing, glassmakers can cut 1 metric ton of CO2 emissions.
Can different coloured cullet be mixed?
Manufacturers use chemicals like iron and chrome oxides to change the color of glass during manufacturing. As a result, different colours should generally not be mixed. Glass retains its colour during the recycling process, and different coloured glass is usually treated as a separate product.
What are some of the contaminants in external cullet?
Organics: Paper, plastics, caps, rings, PVB foils for flat glass
Inorganics: Stones, ceramics, porcelains
Metals: Ferrous and non-ferrous metals
Heat resistant and lead glass (Borosilicate glass)
Usually, external cullet is sorted to ensure there are no contaminants interspersed with the cullet. If cullet gets contaminated it might lead to production losses during manufacturing.
Who does Terraglass accept glass from?
We usually purchase glass from car dealerships, local glass industries, glass scrap collectors, and construction sites in and around Andhra Pradesh, Telangana, and Karnataka. If you work for any of the aforementioned industries, we would love to have a chat with you.
You can reach us out by clicking here.
What types of glass scrap does Terraglass accept?
We only take toughened, laminated, mirrored, and sheet glass scrap. We also accept broken automobile windshield glass.
Will Terraglass take my broken kitchenware glass or glass bottles?
Unfortunately, we do not deal in kitchenware glass or glass bottle cullet.
Does Terraglass buy glass directly from consumers?
It depends on how much glass you have! We usually purchase glass from car dealerships, local glass industries, glass scrap collectors and construction sites. That being said, if you feel you have a large amount of glass scrap (wholesale quantity), feel free to get in touch with us and we will take it from there.
You can reach us out by clicking here.
Who does Terraglass supply glass cullet to?
We supply glass cullet to glass manufacturing industries, construction companies, civil engineering companies, and others who have a wholesale requirement for high-quality glass cullet.