Borosilicate Glass
Definition
Heat-resistant glass with about 80 percent SiO2 and 13 percent B2O3 (boric oxide). Low thermal expansion. Used in cookware (Borosil, Pyrex) and laboratory glassware. Refractive index about 1.47.
- Silica content
- About 80 percent SiO2
- Boric oxide content
- About 13 percent B2O3
- Thermal property
- Low thermal expansion, heat resistant
- Refractive index
- About 1.47
- Common products
- Borosil, Pyrex cookware, laboratory glassware
Common questions
How does refractive index help distinguish borosilicate glass from soda-lime glass at a scene?+
Soda-lime glass, used in most windows and bottles, has a refractive index around 1.51 to 1.52, noticeably higher than borosilicate's roughly 1.47. Measuring refractive index by the Becke line or oil-immersion method lets an examiner assign a fragment to a glass type before any elemental analysis is done.
Why does borosilicate glass matter in fire scene investigation?+
Its low thermal expansion means it resists cracking under rapid heating far better than ordinary soda-lime glass, so intact borosilicate cookware or lab glassware recovered at a fire scene can indicate localised rather than intense uniform heat, and fracture patterns in it are read differently from window glass fractures.
Related terms
- Concentric Crack
- A crack that runs in roughly circular arcs around the point of impact, joining radial cracks. The 4C rule applies: Concentric cracks...
- Float (Pilkington) Glass
- Sheet glass manufactured on a bath of molten tin. The tin-contact face fluoresces under short-wave UV, which lets the analyst orient a...
- Laminated Glass
- Two glass sheets bonded with a polyvinyl butyral (PVB) interlayer. Cracks but does not shatter. Standard for windshields and bank counters. The...
- Radial Crack
- A crack that runs outward from the point of impact, like spokes of a wheel. The 3R rule applies: Radial cracks have...
- Soda-Lime Glass
- The commonest glass family. About 72 percent SiO2, 14 percent Na2O (from soda ash) and 10 percent CaO (from limestone), with small...
- Tempered Glass
- Glass heat-treated to introduce compressive surface stresses and tensile core stresses, producing a material four to five times stronger than annealed glass...
- Wallner Lines and Hackle Marks
- Wavy curved lines (Wallner) and step-like ridges (hackle) on a fracture surface that record the direction the crack front was moving. Used...