GlassWorking Flashcards
What is the primary component of most glasses, and what proportion does it make up in the composition ?
Silica (SiO2) Making up 75% of the composition
Why is glass considered non-crystalline, and how does it differ from other ceramics ?
Glass has o non-crystalline or vitreous structure ( that contributes to the transparency of glass) which distinguishes it from traditional and new ceramics that have crystalline structure.
What is the purpose of annealing in glassmaking ?
To relieve internal stresse and eliminate temperature gradients
At what temperature annealing is typically done
About 500C (900F)
Describe the float process for making flat glass.
In the float process, molten glass flows onto the surface of a molten tin bath. This process ensures that the glass achieves uniform thickness and smoothness, eliminating the need for grinding and polishing
What are the three primary categories of shaping processes used in glass working ?
1- pice ware : used for bottles,jars…( eg: blow-and-blow method)
2- continuous : used for flat glass or tubing ( eg: float process)
3- Fiber-making : used to produce fibers for insulation and fiber optics
How is tempered glass different from regular glass ?
Tempered glass is heated above the annealing temperature and then quickly cooled making the surface in compression while the interior is in tension
Properties of tempered glass and appliations
Resistant to breaking and scratching and it is used in applications like safety glasses, widows for tall buildings and all glass doors
What role do stabilizers play in glass composition?
Stabilizers increase the strength and durability of glass and help to remove bubbles. ( eg: Aluminum Oxide Al2O3; limestone CaO)
Explain the difference between the press-and-blow and blow-and-blow methods
• Press-and-blow: a bob of molten glass is pressed into mold to create wide-mouth containers
• Blow-and-blow : the glass is first partially shaped by blowing air into a mold and then re-blow into its final shape, commonly used for narrow-neck containers like bottles
What is the Danner process ?
It is used to produce glass tubes. In this process, molten glass flows around a rotating mandrel, and air is blow through the mandrel as the glass is drawn to create tubular structures.
Why are automobile windshield made with laminated glass instead of tempered glass?
Laminated holds splinters in place unpin impact preventing dangerous fragmentation while tempered glass shatters into small fragments which could pose a safety hazard.
What product design considerations should be taken into account when working with glass ?
1 - Glass should be used in applications that emphasizes compressive stresses instead of tensile stresses
2 - For applications requiring thermal shock resistance, low thermal expansion coefficients glass should be selected
3 - Avoid sharp corners to minimize stress concentration
