Dental Stone
Definition
A gypsum-based casting material harder and finer than plaster of Paris. Preferred for forensic 3-D casts because it captures detail at the millimetre scale and resists chipping. Standard mix is about 1 lb of stone to 250 mL of water.
- Material
- Calcium sulphate hemihydrate (gypsum-based)
- Standard mix ratio
- 1 pound stone to 250 mL water
- Key advantage
- Captures fine detail at millimetre scale and resists chipping
- Common use
- 3D casting of footprints, tyre marks, and shoe marks in soil and sand
Common questions
Why is dental stone better than plaster of Paris for forensic casts?+
Dental stone is harder, finer, and more durable. It captures fine detail down to the millimetre scale and resists chipping during handling and storage, which is critical for evidence that may be examined repeatedly or presented in court.
What is dental stone made of?+
Dental stone is calcium sulphate hemihydrate, a gypsum-based casting material available in Type III or IV formulations. The standard forensic mix is roughly 1 pound of stone powder to 250 millilitres of water.
When would a forensic investigator use dental stone?+
Dental stone is the standard material for three-dimensional casting of impression evidence like footprints, shoe marks, and tyre marks in soil or sand. It follows SWGTREAD guidelines for tire and footwear evidence.
Related terms
- 2-D Impression
- A two-dimensional print on a hard, flat surface (tiled floor, polished cement, paper). Lifted with electrostatic dust lifter (ESLA), gel lifter, or...
- 3-D Impression
- A three-dimensional impression in a soft medium (mud, sand, soil, snow). Photographed in situ with scale and oblique light, then cast with...
- Class Characteristic
- A feature shared by an entire group of objects (every shoe of one model has the same sole tread; every tire of...
- Class Characteristics (Footwear)
- The manufactured outsole design features shared by all examples of a specific shoe model: tread pattern, size, shape, and logo placement.
- Drag Factor (μ)
- The effective coefficient of friction between the tyre and the road surface during a braking event. Used in the skid-mark speed formula....
- ESLA (Electrostatic Dust-Print Lifter)
- A device that applies a high-voltage static field to a metallised film, attracting dust particles from a footwear impression on a hard...
- Gait Pattern
- The geometric and rhythmic signature of a person's walk. Captured as stride length, step length, cadence, foot angle and walking line. Used...
- Individual Characteristic
- A characteristic unique to a specific typewriter unit arising from manufacturing variation or service wear; used to identify or eliminate a specific...
- Perpendicular Camera Alignment
- The requirement that the camera lens be directly above the impression centre with the sensor plane parallel to the impression plane; prevents...
- R V. Mohan (1994) + White Burgess Langille Inman (2015)
- Canadian Supreme Court framework for forensic-expert admissibility: Mohan sets relevance + necessity + qualification + no exclusionary rule; White Burgess adds an...
- Randomly Acquired Characteristics (RACs)
- Post-manufacture features (cuts, gouges, embedded material, crack patterns) unique to a specific shoe sole or tyre; the highest-level individualising features in impression...
- SICAR (Shoeprint Image Capture and Retrieval)
- FBI and Foster and Freeman (UK) outsole design database used for class-characteristic database searches; referenced in US, UK, Australian, and Canadian forensic...
Explained in these topics
- Impression Evidence: Footprints, Tyre Marks and CastingType III or IV calcium sulphate hemihydrate (gypsum) casting medium for 3D impression casting in soil and sand; the standard forensic casting material per SWGT...
- Track Marks: Foot, Shoe, Tire, Skid Marks and Gait PatternA gypsum-based casting material harder and finer than plaster of Paris. Preferred for forensic 3-D casts because it captures detail at the millimetre scale and...