CLASSIFYING GLASS

• Color

• Thickness

• Curvature

• Surface Texture

• Density

  • d=m/v

  • Find the mass: use a scale

  • Find the volume: water displacement with a graduated cylinder

  • Find the density: flotation method

    • Using liquids with various densities, mix liquids until glass is suspended in the liquid.

    • Density of the liquid = Density of the glass

    • Measure the density of the liquid

• Refractive Index

  • immersion method

  • Snell's law

  • we are going to use the idea that the glass will disappear if we can find an oil that has that has the same Refractive index

  • Use the Becke line as a guide to how close you are to the refractive index.

  • The Becke line is on the side of the substance that has the higher refractive index.

  • The edge of the glass fades as it gets close to a matching refractive index.

  • Refractor Index

    • Color fringe high: above line

    • Color fringe low: below line

    • Color fringe right: meets at center

• Trace Elemental Analysis

  • Through the manufacturing process, the glass picks up trace amounts of metals that it comes in contact with. These elements can be quantitated and used as a “signature” to the factory and even the batch number.

• Gemstones

  • Gemstones can also be identified through density and refractive index.

  • Some of them also have birefringence.

  • Bifringence: Some substances (synthetic fibers, some crystalline solids) have two different refractive indices depending which way the light passes through the substance. These substances will polarize light and can be seen and measured on the polarizing microscope. Glass does not have birefringence

  • Birefringence = | RI1-RI2 |