Glass manufacturing is a large consumer of many industrial
minerals, including soda ash, quartz and limestone. It is also
used in a wide variety of industries, such as construction,
manufacturing and home ware. But with the economic recession
still leaving a trail of devastation in many industries, how
will the glass supply chain fare in 2013?
Glass is an amorphous, non-crystalline solid material
recognised for its low-cost suitability for many everyday uses
including transparent panes and receptacles. While the
adaptability of glass to many different products and
applications is recognisable, the use of industrial minerals in
its formation is by no means limited - especially considering
the variations between glass type and glass manufacturing
The most familiar and commonly produced type of glass is
soda-lime glass. This glass is used widely in two main types -
flat glass, designed for end uses such as window panes and in
the automobile industry, and container glass, used to make
receptacles such as tablewear and bottles.
Soda lime glass is produced using minerals such as soda ash,
quartz (silica) and lime.
Glass can also be defined in a much wider sense to include
every solid that possesses a non-crystalline, amorphous
structure that exhibits a glass transition when heated towards
the liquid state.
In this wider sense, glasses can be made of different classes
of materials including metallic alloys, ionic melts, aqueous
solutions, molecular liquids and polymers. For many
applications, polymer glasses, such as acrylic glass,
polycarbonate, polyethylene terephthalate, are a lighter
alternative to traditional silica glasses.
Glass manufacturing is complex and encompasses an enormous
range of compositions and product types. Materials for
glassmaking can be classified in three groups: glass formers,
fluxes and stabilisers.
Soda lime glass is composed of approximately 75% silica
(SiO2), sodium oxide (Na2O) from soda
ash, lime (CaO) and several other minerals including stibnite
(the main ore of antimony) and feldspar. The mix of minerals
used to make soda-lime glass is termed batch.
The glass is produced by melting the batch in a glass furnace
at temperatures of up to 1,675¡C (3,047¡F). The
temperature of the furnace is limited by the quality of the
furnace superstructure material, that is whether it can
withstand higher temperatures, and by the glass
In the process of melting [solid to liquid] a viscous
liquid is formed and the mass becomes clear and homogeneous at
temperatures above 1,000 ¡C. When removed from the
reactor, the glass acquires a shape allowing handling. By
controlling the temperature of cooling, [this] avoids
devitrification or crystallisation, Felix Antonio
Martinez Sendoya, Colombian Silicas CEO of silica and
business, told IM.
Relatively inexpensive minerals, such as soda ash, sand and
feldspar, are added to the batch as fluxing agents to reduce
the melting temperature of quartz and help to control the
viscosity of glass.
For minerals such as feldspar (p74), the alkali
content acts as flux, lowering the glass-melting temperature
and thus reducing production costs. Coloured glass, such as
that used to make green and brown bottles, is produced from raw
materials containing iron oxide (see
A typical batch for clear glass containers may consist of 155kg
soda ash, 172kg limestone, 145kg feldspar and 5kg sodium
sulphate. Flat glass batches require about 115kg of soda ash
per 450kg of silica sand used [Industrial Minerals and
Rocks, 7th Edition].
Importantly, the manufacturing process [to make glass] is
practically the same for all types; [what] changes from one
specimen to another is the material. All of them have a greater
or lesser proportion of silicon atoms, Sendoya told
While the materials used to make flat and container glass come
from the same mineral batch, the physical process used to
create the finished glass differs slightly.
For flat glass, the float process is administered, while for
containers, glass blowing is performed. Float glass has a
higher magnesium oxide and sodium oxide content compared with
container glass, and lower silica, calcium oxide and aluminium
oxide content. This means that the quality of container glass
is higher, mainly due to the fact that it is required to be
safe for use as homeware receptacles (for chemical durability
Industrial sand and gravel, often called silica, silica sand or
quartz sand, includes sands and gravels with high silicon
dioxide (SiO2) content. Silica is the major ingredient in
virtually all types of glass including containers, flat glass,
lighting glass, tableware, TV tubes and screens, decorative
glass, fibreglass, optical glass and vacuum flasks. The
commercial uses of glass (containers, windows, vehicle glazing)
contain between 70 - 74% silica, the ultimate source of which
is silica sand.
Glass manufacturers are principally concerned with the chemical
composition of silica sands, particularly iron, chromite and
other refractory mineral contents, according to the British
Geological Survey (BGS).
Quality requirements depend on the type of glass being
manufactured - whether it will be coloured or clear - and to
some extent on the requirements of the individual glass
manufacturer. Silica sand for colourless glass containers
generally has an iron content of <0.035%
Fe2O3 (ferric iron oxide), for flat glass
in the range 0.040 to 0.1% Fe2O3 and for
coloured glass containers 0.25% to 0.3%
Global sand resources are large and widespread and somewhat
unquantifiable. However, in terms of production, 140m tonnes
silica sand was produced in 2012, according to the US
Geological Survey (USGS). Some 49m tonnes of this sand were
produced in the US, with around 17% of this being used to make
While resources and production are on a large scale, several
limitations surrounding silica sand exist worldwide including
geographical distribution - which can often be a costly and
uneconomic practice - environmental restrictions - related to
potential health risks associated with the use of silica sand -
and quality requirements for use, as outlined above.
The glass industry is the largest consumer of soda ash,
particularly the glass-container sector. Soda ash has been used
in glass manufacturing for more than 5,500 years
[Industrial Minerals and Rocks, 7th
Edition] and continues to be used in the industry
Soda ash is a source of sodium oxide that is used as a fluxing
agent in container, fibre, and speciality glass manufacturing
to reduce the temperature at which the raw materials, such as
silica sand, melt. Soda ash also decomposes into sodium oxide
and carbon dioxide, which rises through the glass melt and
helps mix the ingredients.
In terms of supply, China continued to dominate last year,
producing 23m tonnes in 2011, according to latest USGS data.
The US followed, producing 14.5m tonnes in 2011, with a total
value of approximately $1.3bn.
China continues to be the largest and fastest-growing
market for soda ash. Due to its size and the persistent
over-capacity in the Chinese industry, it also has a strong
impact on important markets for soda ash trade - Asia, and to a
lesser extent, Latin America, FMC Corp., the Wyoming,
US-based producer, told IM.
However, while the usual players are continuing to produce
within expectations, there are new entrants to the market,
including some from developing countries.
In developing countries, the soda ash [market] is growing
by 5%; in the US and Europe demand is stable. Total growth is
2m tpa - 1m tpa in China [and] 1m in the rest of the
world, Novacarb, the France-based soda ash producer, told
Turkey is a country that emerged as a key soda ash producer in
2012, with more than 2m tonnes of capacity logged in
China continues to lead the way for new capacity coming
on-stream, and Turkey has emerged as a new player with good
access to European and Middle Eastern markets, Dennis
Kostick at the USGS told IM.
The recycling of glass has brought the cost of domestic
container glass manufacturing down by significant amounts as
cullet, the mixture of used glass broken down to be recycled,
is used to replace part of the silica requirements in a glass
batch. Cullet also has a much lower melting temperature -
around 20-25% below a conventional batch - further reducing the
cost by lowering the amount of flux required.
Glass recycling is an increasingly important input into
container glass production. [É] more than 68% [2010
data] of glass bottles and jars put on the market are collected
for recycling and most of them [some 80%] are recycled in a
bottle-to-bottle, closed-loop recycling system, the
European Container Glass Federation (Feve) told
[This means] that, once produced, glass can be used over
and over again without down-cycling and by reducing use of new
minerals and raw materials and preventing waste generation.
Glass is mono-material and does not require any additional
barriers to preserve food and drinks, making its recycling
particularly easy. This is a good illustration of how a
circular economy for packaging can work, Feve
For every tonne of recycled glass, 1.2m tonnes of virgin raw
materials are saved in the melting process, according to the
federation. This is extremely important for the container glass
industry because by using recycled glass also reduces the
amount of energy used and CO2 emitted.
It has a big contribution to the sustainability of the
industry. That is why some of the mineral suppliers (for
example Sibelco) are investing in recycling facilities (for
example Pate), Feve told IM.
While this is positive news for container glass manufactures,
it is not so good for soda ash producers, which have seen
decreased demand since the worldwide push to recycle got
underway in earnest.
Feldspar acts as a fluxing agent in glass making and is used to
bring the melting temperature of silica down. It is also a
stabiliser. Stabilisers impart to the glass a high degree of
resistance to physical and chemical attacks. Fluxes are oxides,
including potassium oxide (K2O) and sodium oxide
(Na2O) and stabilisers can be oxides such as alumina
(Al2O3) [Industrial Minerals and Rocks,
During glass manufacture, feldspar has two functions, acting as
a flux by providing alkaline oxides (K2O and
Na2O) and as a stabiliser by providing alumina and
calcium oxide. A typical batch for container glass contains
around 8% feldspar, according to Roskill Information
Feldspar is the most abundant group of minerals in the
Earths crust, forming about 60% of terrestrial rocks.
Feldspar reserves are found in various countries, including
India, Czech Republic, Portugal and Poland among others. Turkey
and Italy are the top two producing countries, accounting for
about 50% of the world production with almost 10m tpa in 2012,
according to USGS estimates.
Identified and hypothetical resources of feldspar are more than
adequate to meet anticipated world demand, the USGS added,
which states that quantitative data on resources of feldspar
existing in feldspathic sands, granites, and pegmatites
generally have not been compiled.
Ample geologic evidence indicates that resources are
large, although not always conveniently accessible to the
principal centres of consumption, it said in its most
recent feldspar report.
Other materials that can be used for glassmaking include
fluorspar, lime, chromite, olivine, staurolite and zircon
sands, according to the USGS.
Glass markets: handle with care
Soda-lime glass, while the most abundantly manufactured form of
glass, has experienced testing times during the past few years
as the global economic crisis significantly slowed the amount
of new building as well as the amount of manufacturing
Glass was hit hard by a crash in the global housing market
during the period 2008-2012. This collapse, in turn, caused the
prices for some minerals used to produce glass - such as soda
ash - to dip to the point where prices for the mineral were as
low as they can feasibly go.
Other glass-using industries, such as automobile manufacturing,
also took a knock, which again filtered down to the raw
materials demand level.
Despite this, international chemicals company Solvay, the
worlds number one synthetic soda ash producer, said that
a drop in demand for flat glass in the construction and
automotive industries was buoyed by strong performance in the
container glass sector.
Feve agreed with this statement, telling IM:
The container glass industry produces some 20m tpa glass.
In terms of tonnage, the biggest markets for the container
glass industry is the beverage sector. Beer, spirits and wines
account for the largest share. Overall, glass packaging
represents one-third of the European beverage market in
While the beverage market is important, the food sector
is increasingly offering an important growth opportunity for
glass packaging. This is certainly linked to new market trends
orientated by consumers demand for high-quality, natural,
organic food. More than any other material, glass can best
communicate to consumers these product characteristics. Glass
is a packaging reference for brands and for consumers,
the federation added.
While some glass markets dipped in 2012, this year has already
begun to show some promise. In the housing sector, for example,
23 markets have demonstrated better year-on-year statistics in
Q3 2012 compared with Q3 2011, according to a report by
Global Property Guide. Recovery of the US housing
market has been particularly evident, with growth in Q3 2012
being the highest since Q2 2006, according to the Federal
Housing Finance Agency (FHFA), the Guide
Certainly our sector saw a dip during the crisis years,
but we see that we are now almost back to the pre-crisis levels
in terms of tonnage. According to latest available figures [H1
2012], glass packaging production volumes in Europe grew by
1.9%. The growth is in response to the increasing demand on the
domestic and outside EU markets. This builds on the positive
trend recorded in 2011, Feve told
Despite the unstable economic and financial crisis that
negatively affects the whole European manufacturing sector,
these records shed a positive light on the stability and future
prosperity of the European container glass sector. This is
certainly due to the fact that consumers continue to have a
strong preference for glass - 74% of consumers would recommend
glass as a packaging material [Insites 2010], the
Despite these encouraging results, the impact of the global
economic crisis is still evident across the glass
Increased production costs, unilateral CO2 costs,
fluctuating and unfavourable exchange rates, and high labour
costs hamper the cost competitiveness at global level of the
container glass sector, Feve said,
Combined, these challenges delay long-term investment
decisions and, rather, become incentives for delocalisation of
production sites and R&D investments outside EU to more
industry friendly environments with lower costs, it
Glass fibre is made up of bulk, chopped fibres or strands of
glass and durable plastic resin. It is used in reinforcing
plastics and composites as well as other specialised electrical
and thermal applications.
Minerals used in the creation of glass fibre are similar to
those employed in the creation of other forms of glass. These
include silica sand, limestone, soda ash, borates, kaolin,
lithium minerals, potash, feldspar, fluorspar and sodium
The most common glass fibre is a calcium-alumina borosilicate
with an alkali content of less than 1%. It is commonly known as
e-type glass, since it was originally developed for use in
electrical insulation systems.
E-type glass was created in the 1950s to insulate electronics.
Today, uses for glass fibre include mats, thermal insulation,
electrical insulation, sound insulation, reinforcement of
various materials, tent poles, sound absorption, heat- and
corrosion-resistant fabrics and automobile bodies.
Glass fibre is used in consumer goods such as hot tubs, bath
tubs and boats. It is also used in water storage tanks, for
pipes in the oil and gas industry, as well as in households and
offices, in roofing and cladding.
Glass fibre production
Glass fibres are produced by running molten glass from a
direct-melt furnace into a platinum alloy bushing containing a
large number of small holes, from each of which a glass
filament is drawn.
Filaments for commercial use are normally between nine and 15
microns in diameter. The filaments are layered with an emulsion
before being gathered into fibres.
The fibres are strong and they have excellent electrical
properties. They are also resistant to most chemicals and
moisture wear. They are non-combustible, with a melting point
Glass fibre industry
The fastest-growing industry sector for glass fibre is in
insulation, as populations become more concerned with energy
conservation. The European Unions push to improve energy
consumption by 20% by 2020 has seen many governments offer free
or subsidised insulation and this is welcome news for glass
fibre minerals such as kaolin and borates.
Outside of the EU, Russia is aiming to reduce energy
consumption by 40% in 2020 and China has invested heavily in
rebuilding energy poor housing and has pledged
$23bn for energy efficient projects.
The Obama administration in the US has launched ambitious
energy-saving initiatives, including a $2,000 tax credit for
residential homeowners who insulate properly and make their
existing properties more energy efficient.
In Australia, the government pledged in 2009 to install free
ceiling insulation in around 2.7m homes under the Energy
Efficient Homes Package. However, the Home Insulation Programme
was later shelved in favour of a new scheme and then abandoned
in April 2010. The scheme was controversial, due to worker
fatalities while installing the insulation, and costly, due to
The fact that glass is faced with economic challenges is viewed
as a minor hurdle for many working in the industry, even at the
industrial minerals level, as glass remains the number-one
option industrial minerals producers of borates, silica sand
and soda ash. This is because it is used for many industries
including automobile, tableware, cosmetics and
This continued market demand will, in turn, increase the call
for industrial minerals such as soda ash, silica, limestone and
fluxes including feldspar.
Glass is also classed as a material of the future as it is
recyclable, re-usable and refillable.
This makes it certainly a reference for the circular
economy - where there is a big change from the linear economy
model to the circular model. This is based on recycling, which
closes the loop, Feve said.