Sieve Analysis
Definition
Mechanical separation of soil particles by passing a dried, dispersed sample through a stack of sieves with calibrated apertures from 2 mm down to 63 micrometres, then weighing each retained fraction.
- Sample prep
- Dried and dispersed before sieving
- Sieve range
- 2 mm down to 63 micrometres
- Method
- Stack of calibrated sieves, weighing each retained fraction
- Forensic use
- Soil particle size profile for comparing questioned and reference samples
Common questions
Why does sieve analysis stop at 63 micrometres rather than measuring finer particles?+
Mechanical sieving becomes impractical below roughly 63 micrometres because particles clump and clog the mesh; finer clay and silt fractions below that threshold are instead characterised using techniques such as laser diffraction or sedimentation, so sieve analysis is typically paired with those methods for a complete particle size profile.
How is a sieve analysis result used to compare two soil samples forensically?+
The weight percentage retained on each sieve size produces a particle size distribution curve for each sample; an examiner compares the shape and proportions of these curves between a questioned sample, such as soil on a shoe, and a reference sample from a scene, looking for consistency or clear divergence.
Related terms
- Hydrometer Method
- A sedimentation technique that uses Stokes' Law to determine the proportion of silt and clay from the rate at which particles settle...
- Laser Diffraction
- An instrumental method where a dispersed sample passes through a laser beam and the angular diffraction pattern is inverted to produce a...
- Particle-Size Distribution (PSD)
- The proportion by mass of soil particles falling within each size fraction. Expressed as a curve or a table of percentages, and...
- Ribbon Test
- A field method for estimating texture by wetting a small amount of soil and extruding it between thumb and finger. The length...
- Textural Triangle
- A ternary diagram with sand, silt, and clay at the three apices. A point plotted from the measured percentages of those three...