silica and moulding sands association (samsa) part of the Mineral Products Association (MPA)
 

samsa

silica and moulding
sands association

 
 

Silca uses

Glass

High quality silica sand makes up around 70% of the batch of ingredients that is used to make glass. The other 30% is made up of soda ash and dolomite, which act as fluxing agents, along with a percentage of recycled glass.

Glass manufacturers make substantial investments in their furnaces, which have a lifespan of at least 15 to 20 years. Not surprisingly, they expect their supply of high quality silica sand to be assured for many years. Long term consistency is a key factor when supplying the glass industry.

The particle size distribution of the sand grains is also a key factor when producing silica sand for glass making. The sand grains can’t be too coarse, otherwise they will not melt efficiently in the furnace and this could cause some of them to remain as blemishes in the finished product. If the sand grains are too fine, then they will get sucked up into the airflows of the furnace heat regeneration systems, causing them to be lost. Ideally, an even spread of grain sizes is needed in order to encourage “fluxing”, where larger particles are melted by the ones that are already melted.

Another key factor in selecting silica sand for glassmaking is the chemistry of the sand, with different chemistry being needed for different types of bottles. For example, milk and vodka bottles are colourless, having no green tinge. Beer bottles are often brown or green, with brown glass offering greater protection against damage caused by ultraviolet light. Levels of iron oxide, chromes, zircon and metals (including alumina) are all strictly controlled in order to ensure that the silica sand meets the requirements and expectations of both the glassmaker and the end consumer.

For our country’s supply of high quality silica sand for glass making, we are reliant upon naturally occurring deposits that are very rare. Silica sand for glass making makes up only a tiny proportion of all mineral sands that are extracted, but the supply is sufficient to make billions of bottles, jars, medical and scientific glass, windows and windscreens, smart phone and tablet screens. These products all play an essential role in our everyday lives and we take many of them for granted.
Glass is unique in that it can be recycled 100% time after time, but there is always a need for high quality silica sand to keep the glass makers’ furnaces running.

 
 
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