Module: U12M1 - Glass Science and Safety
Passing Score: 70%
What is the primary chemical component of all common glass types?
Explanation: Silica (SiO₂) forms the fundamental network structure of glass, typically comprising 50-99% of the composition depending on glass type.
Which glass type has the lowest coefficient of thermal expansion (CTE)?
Explanation: Fused silica has the lowest CTE at 0.5 x 10⁻⁶ /K, making it virtually immune to thermal shock. This is because it is nearly pure SiO₂ with no network modifiers to disrupt the silica structure.
What happens when soda-lime glass and borosilicate glass are fused together in a kiln?
Explanation: Soda-lime (CTE 9) and borosilicate (CTE 3.3) have incompatible thermal expansion rates. During cooling, the soda-lime contracts more than the borosilicate, creating internal stress that causes crazing or complete breakage.
What is the purpose of the annealing process in glass working?
Explanation: Annealing heats glass to its annealing point (e.g., 510°C for soda-lime) and holds it there to allow internal stress to relieve through atomic rearrangement, then cools slowly to prevent new stress from forming.
At what temperature does soda-lime glass reach its annealing point?
Explanation: The annealing point for soda-lime glass is approximately 510°C. At this temperature, internal stress relief occurs over a timescale of hours. Below the strain point (475°C), glass becomes permanently stressed.
Which type of eye protection is required when viewing the interior of a hot kiln?
Explanation: Hot kilns and glass emit significant infrared radiation that causes cumulative, irreversible eye damage including cataracts. UV/IR-rated eye protection filtering 99%+ of UV and IR is mandatory for all kiln viewing and torch work.
What is the primary respiratory hazard when grinding glass?
Explanation: Grinding glass produces fine silica dust particles. Chronic inhalation causes silicosis, a progressive lung fibrosis with 10-20 year latency. This is a silent hazard with no acute symptoms. Wet grinding is the primary prevention method.
What is the correct first aid response for a thermal burn from hot glass?
Explanation: Cool running water for 10-20 minutes is the correct response. Ice causes additional tissue damage. Oil and butter trap heat. The goal is gradual cooling without secondary injury.
Why is lead glass considered a critical hazard material?
Explanation: Lead oxide (PbO) in lead glass is neurotoxic and bioaccumulative. Even small exposures contribute to lifetime lead burden. Grinding produces lead-containing dust requiring wet grinding, HEPA filtration, and PAPR protection.
What does the thermal color "bright cherry red" indicate about soda-lime glass temperature?
Explanation: Bright cherry red indicates 800-900°C (1470-1650°F). At this temperature, glass is extremely hot and any contact will cause instant severe burns. Full PPE is required and direct contact is prohibited.
Which glass type is recommended for torch/lamp work?
Explanation: Borosilicate's low CTE (3.3 x 10⁻⁶ /K) gives it superior thermal shock resistance, allowing it to withstand the rapid heating and cooling cycles inherent in torch work without cracking.
What is the minimum clearance required around a hot kiln during operation?
Explanation: A 3-foot clearance perimeter is required around hot kilns because heat radiates outward from all surfaces. This zone must be marked with warning tape or signs and kept clear of personnel and materials.
What is thermal shock in glass working?
Explanation: Thermal shock occurs when glass experiences a sudden temperature change. The surface cools (or heats) rapidly while the interior remains at a different temperature, creating extreme stress that exceeds the glass's strength, causing instant fracture.
What is the correct PPE donning sequence before kiln or torch work?
Explanation: The correct sequence ensures extremity protection first (gloves), then eye protection (glasses), then face coverage (shield), then body protection (apron), and finally securing loose items. This order minimizes exposure during the donning process itself.