Sieve Analysis of Raw Materials for Glass Manufacture: Method & Standards
Introduction to Sieve Analysis in Glass Manufacturing
The manufacture of high-quality glass — whether flat glass, container glass, optical glass, or speciality glass — depends critically on the consistent particle size distribution of raw material batches. Silica sand, soda ash, limestone, dolomite, feldspar, and glass cullet (recycled broken glass) must be carefully sized to ensure homogeneous melting, minimal defect formation, and consistent glass composition in the final product.
Sieve analysis is the primary method for characterising the particle size distribution of glass batch raw materials, governed by standards including ASTM C92 (sieve analysis of batch materials for glass manufacture) and ASTM C429 (sieve analysis of raw materials for refractory products).
Why Particle Size Distribution Matters in Glass Manufacturing
Melting Efficiency and Homogeneity
The particle size of raw materials directly determines the rate and completeness of dissolution in the glass melt. Coarse silica particles dissolve slowly, requiring higher melt temperatures, longer residence times, or leaving undissolved “stones” in the glass. Fine particles dissolve rapidly but may cause bridging in batch hoppers and uneven feeding.
Batch Segregation
Wide particle size distributions in mixed glass batches cause segregation — lighter, smaller particles separate from coarser ones during conveying and feeding, causing compositional variability in the melt and glass property non-uniformity.
Defect Formation
Oversized silica grains that fail to dissolve completely in the melt become “stones” — solid inclusions that are major glass defects causing optical distortion, stress concentrations, and potential spontaneous fracture. Sieve analysis detects and controls oversize fractions that generate stone defects.
Foam and Gas Release
Fine, dust-sized particles below 100 µm can entrap gas and promote excessive foaming during batch melting. Sieve analysis specifications include lower limits as well as upper limits to control fines content.
ASTM C92 Test Procedure
ASTM C92 specifies the following test procedure for glass batch raw materials:
- Dry the representative sample to constant mass at 110°C
- Weigh the dried sample (typically 100–500 g)
- Sieve on a nest of standard sieves (per ASTM E11) for a defined time using a mechanical shaker
- Weigh the fraction retained on each sieve and the pan
- Calculate cumulative percent retained and percent passing for each sieve size
- Compare the resulting gradation curve against the specified limits
Critical Sieve Sizes for Common Glass Raw Materials
For silica sand, the 100 µm (No. 140) and 500 µm (No. 35) sieves are critical — material above 500 µm risks stone formation, while excessive material below 100 µm increases batch dust and foam risk. For glass cullet, sieve analysis characterises the size distribution to prevent feeder blockages and ensure adequate melting rates.
Quality Control Applications
Regular sieve analysis of incoming raw material deliveries verifies supplier compliance with particle size specifications. In-process sampling during batch preparation monitors segregation and particle size consistency. Both incoming and in-process sieve data are critical for maintaining glass melt quality and minimising defect rates in production.
Conclusion
Sieve analysis is a fundamental quality control technique in glass manufacturing, used to ensure the particle size distribution of raw materials remains within specified limits for efficient melting and defect-free glass production. By controlling the size range of silica sand, cullet, and other batch constituents, manufacturers can improve melt homogeneity, reduce segregation, minimise stone formation, and control foaming behaviour. Standards such as ASTM C92 provide a standardised and reproducible framework for this testing. Routine sieve analysis is therefore essential for maintaining process stability, supplier quality assurance, and final glass product performance.
Why Choose Infinita Lab for Glass Raw Material Sieve Analysis?
Infinita Lab provides ASTM C92-compliant sieve analysis for glass manufacturing raw materials through our nationwide accredited analytical laboratory network, with rapid turnaround supporting incoming material inspection and production quality control programmes.
Looking for a trusted partner to achieve your research goals? Schedule a meeting with us, send us a request, or call us at (888) 878-3090 to learn more about our services and how we can support you.
Frequently Asked Questions (FAQs)
What is sieve analysis in glass manufacturing? Sieve analysis is a test method used to determine the particle size distribution of raw materials such as silica sand, cullet, soda ash, and limestone used in glass production.
Why is particle size important in glass making? Particle size affects melting rate, batch homogeneity, defect formation, foaming, and the overall efficiency of the furnace process.
What defects can occur if particles are too coarse? Oversized particles may not fully dissolve and can form stones or inclusions in the final glass.
Why are very fine particles also a concern? Excess fines can lead to dusting, hopper bridging, gas entrapment, and excessive foaming during melting.
What materials are commonly tested by sieve analysis? Typical materials include silica sand, soda ash, limestone, dolomite, feldspar, and recycled glass cullet.
