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Soda–lime glass

Soda–lime glass is a engineering topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Soda–lime glass rather than just read about it. In short: Soda–lime glass, also called soda–lime–silica glass, is the transparent glass used for windowpanes and glass containers (bottles and jars) for beverages, food, and some commodity items. It is the most prevalent type of glass made.

Soda–lime glass — main illustration
Soda–lime glass — illustration

Key takeaways

  • Soda–lime glass belongs to engineering; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Soda–lime glass to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Soda–lime glass from memory before moving on to harder problems.

Reference excerpt

Soda–lime glass, also called soda–lime–silica glass, is the transparent glass used for windowpanes and glass containers (bottles and jars) for beverages, food, and some commodity items. It is the most prevalent type of glass made. Some glass bakeware is made of soda-lime glass, as opposed to the more common and heat-tolerant borosilicate glass. Soda–lime glass accounts for about 90% of manufactured glass.

Production The manufacturing process for soda–lime glass consists in melting the raw materials, which are the silica, soda (Na2O), hydrated lime (Ca(OH)2), dolomite (CaMg(CO3)2), (which provides the magnesium oxide), and aluminium oxide; along with small quantities of fining agents (e.g., sodium sulfate (Na2SO4), sodium chloride (NaCl), etc.) in a glass furnace at temperatures locally up to 1675 °C. The soda and the lime serve as a flux lowering the melting temperature of silica (1580 °C) as well as causing the mixture to soften as it heats, starting at as low as 700 °C. The temperature is only limited by the quality of the furnace structure material and by the glass composition. Relatively inexpensive minerals such as trona, sand, and feldspar are usually used instead of pure chemicals. Green and brown bottles are obtained from raw materials containing iron oxide. The mix of raw materials is termed batch.

Applications Soda–lime glass is divided technically into glass used for windows, called flat glass, and glass for containers, called container glass. The two types differ in the application, production method (float process for windows, blowing and pressing for containers), and chemical composition. Flat glass has a higher magnesium oxide and sodium oxide content than container glass, and a lower silica, calcium oxide, and aluminium oxide content. From the lower content of highly water-soluble ions (sodium and magnesium) in container glass comes its slightly higher chemical durability against water, which is required especially for storage of beverages and food.

Typical compositions and properties Soda–lime glass is relatively inexpensive, chemically stable, reasonably hard, and extremely workable. Because it can be resoftened and remelted numerous times, it is ideal for glass recycling. It is used in preference to chemically pure silica (SiO2), otherwise known as fused quartz. Whereas pure silica has excellent resistance to thermal shock, being able to survive immersion in water while red hot, its high melting temperature (1723 °C) and viscosity make it difficult to work with. Other substances are therefore added to simplify processing. One is the "soda", or sodium oxide (Na2O), which is added in the form of sodium carbonate or related precursors. Soda lowers the glass-transition temperature. However, the soda makes the glass water-soluble, which is usually undesirable. To provide for better chemical durability, the "lime" is also added. This is calcium oxide (CaO), generally obtained from limestone. In addition, magnesium oxide (MgO) and alumina, which is aluminium oxide (Al2O3), contribute to the durability. The resulting glass contains about 70 to 74% silica by weight. Soda–lime glass undergoes a steady increase in viscosity with decreasing temperature, permitting operations of steadily increasing precision. The glass is readily formable into objects when it has a viscosity of 104 poises, typically reached at a temperature around 900 °C. The glass is softened and undergoes steady deformation when viscosity is less than 108 poises, near 700 °C. Though apparently hardened, soda–lime glass can nonetheless be annealed to remove internal stresses with about 15 minutes at 1014 poises, near 500 °C. The relationship between viscosity and temperature is largely logarithmic, with an Arrhenius equation strongly dependent on the composition of the glass, but the activation energy increases at higher temperatures. The following table lists some physical properties of soda–lime glasses. Unless otherwise stated, the glass compositions and many experimentally determined properties are taken from one large study. Those values marked in italic font have been interpolated from similar glass compositions (see calculation of glass properties) due to the lack of experimental data.

Coefficient of restitution (glass sphere vs. glass wall): 0.97 ± 0.01 Thermal conductivity: 0.7–1.3 W/(m·K) Hardness (Mohs scale): 6 Knoop hardness: 585 kg/mm2 + 20

See also Glass batch calculation

References

Illustrations

Soda–lime glass: Reusable soda–lime glass milk bottles
Reusable soda–lime glass milk bottles
Soda–lime glass: Old window made from soda-lime flat glass, Jena, Germany: The distorted reflections of a tree indicate that the flat glass was possibly not made by the float glass process.
Old window made from soda-lime flat glass, Jena, Germany: The distorted reflections of a tree indicate that the flat glass was possibly not made by the float glass process.

Worked examples

Example 1 — a first encounter with Soda–lime glass

Start with the simplest possible case. Write down what Soda–lime glass claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In engineering, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Soda–lime glass before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Soda–lime glass ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Soda–lime glass

In research
Soda–lime glass appears in engineering research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Soda–lime glass in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Soda–lime glass is common in secondary-school and first-year university syllabi. It links to neighbouring topics Glass compositions, Transparent materials, so understanding it makes those chapters shorter.
In everyday life
Look for Soda–lime glass outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.
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How to study Soda–lime glass in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Soda–lime glass means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Soda–lime glass out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Soda–lime glass in simple terms?

Soda–lime glass, also called soda–lime–silica glass, is the transparent glass used for windowpanes and glass containers (bottles and jars) for beverages, food, and some commodity items. It is the most prevalent type of glass made.

Why does Soda–lime glass matter?

Because it connects several engineering ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Soda–lime glass?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Soda–lime glass.

Tags

  • Glass compositions
  • Transparent materials

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