The use of sieves to separate grain sizes is easily traceable to early Egyptian times. However, it was not until the latter part of the 19th century that using a graduated series of sieves with standardized apertures to classify materials by particle size distribution became a widely accepted practice.
From the wire materials then available for weaving mesh, brass quickly came into favor for testing applications. Brass was malleable and easy to weave on looms of that time yet durable enough to maintain the opening tolerances required for testing sieves. Brass was also corrosion-resistant, cost-effective, and widely available. For this blog article, we will look at the use of brass for weaving the mesh of laboratory test sieves and how stainless steel has become a more efficient and cost-effective mesh material.
High-Quality Brass Sieves
80/20 brass wire consists of about 80% copper and 20% zinc, with small amounts of lead and iron. This alloy is used to weave sieve meshes with openings from 2.36mm to 212µm (№ 8 to № 70). Finer mesh sizes are typically woven with phosphor bronze wire, an alloy of copper, tin, and phosphorous often referred to informally as brass.
Right through the late 20th century and beyond, brass remained the predominant mesh material for test sieves. Still, the properties that make brass so easy to weave into accurate mesh sizes were a limiting factor in the service life of the finished test sieve. The malleability of brass meant that excessive sample loadings could stretch the mesh and deform the openings, while samples with abrasive qualities would grind away at the brass wires and enlarge the apertures. With no suitable alternatives aside from brass wire, users and producers took these faults in stride, replaced their sieves more frequently, and learned to live with the limitations of the material.
Introduction of Stainless Steel
Around this time, stainless steel was gaining recognition for its distinct advantages as a mesh material for test sieves. Producers were finding alloys with better weaving characteristics and adapting their machinery to better suit stainless steel's harder, stiffer properties. Stainless steel was becoming a clear favorite for the particle sizing of materials sensitive to contamination, abrasive compounds, or samples with high unit weights. With much greater strength and resistance to deformation, abrasion, and corrosive compounds, stainless steel was a low-maintenance alternative for the gradation analysis of many materials.
High-quality stainless steel testing sieves were undeniably the best choice for durability, low contamination levels, and serviceability, but price was still a big obstacle. In testing labs, brass sieves were suitable for most particle sizing applications, and while durability was lower by comparison, brass was still cost-effective over the long term.
Market Forces Bring Changes to the Laboratory
The cost of brass has risen sharply in the past decade, driven mainly by the increasing cost of copper. At the same time, stainless steel alloys have become widely available with more stable pricing. Although some types of sheet or ingot brass remain less expensive, the comparative price of woven wire brass mesh is now higher. A side effect of this shift toward stainless steel mesh has been that production of brass mesh is now limited to opening sizes from 2.36mm to 45µm (№ 8 to № 325).
Wire mesh producers have learned to adapt their tooling, manufacturing processes, and raw material inventories to changing price structures and availability in the metals market. For once, a significant change in industry practice comes packaged as an opportunity rather than an imposed burden.
Gilson stocks stainless steel test sieves with openings from 125mm to 20µm (5in to № 635) in all standard ISO and ASTM test sieve frame diameters. Stainless steel sieve mesh is woven from 304 stainless wire for openings from 125mm to 2.8mm (5in to № 7) and for 20µm (№ 635). Mesh sizes from 2.36mm to 25µm (№ 8 to № 500) are woven with a 316 stainless steel alloy. A 305 alloy is used for all stainless steel frames.
In nearly every aspect, a test sieve with stainless steel mesh and frame is a better choice than a sieve made from brass, and it is generally available at a 10% to 15% lower price point. Factoring in the longer accurate service life of stainless steel mesh means even greater cost savings.
Brass Test Sieves are Still Available
Gilson has long offered a choice of brass or stainless steel test sieves to meet the needs of the most demanding particle sizing applications. Even with the limitations on available opening sizes, we will continue to offer brass mesh sieves because they are valid testing instruments and meet all the same ASTM and ISO requirements as their stainless steel counterparts. Still, we want to help our customers identify and select top-quality products with lasting value.
One exception for the suitability of stainless over brass is when testing materials where sparking would create a hazardous condition. Sieves with brass frames and brass mesh are always recommended when testing in potentially explosive environments.
An option for those who prefer it, "combination" test sieves are constructed with 85/15 brass frames and a full range of stainless-steel mesh sizes. The skirt (the bottom part of the frame that nests with a finer sieve or dustpan) is stainless steel to resist abrasion when fitted together with other sieves.
Combination sieves were introduced originally as an economical alternative to stainless steel test sieves, but as noted above, market forces have shifted materials costs. These models are currently at a price similar to fully stainless steel versions. The brass frames are less resistant to dents and deformations that can cause uneven tension and variability in the apertures of the wire cloth. Stainless steel frames resist rough handling and better hold the mesh at the proper tension.
We hope this article has helped you decide on the best type of material for your new test sieves. Please contact our Testing Experts at Gilson to discuss your testing application.
Additional Resources
Gilson Videos:
Specifications and References:
- ASTM Test Sieving Methods, (Manual 32) Guidelines for Sieve Analysis Procedures
- ASTM E11, Standard Specification for Woven Wire Test Sieve Cloth and Test Sieves
- ISO 565, Test sieves — Metal wire cloth, perforated metal plate, and electroformed sheet — Nominal sizes of openings
- ISO 3310-1, Test sieves — Technical requirements and testing — Part 1: Test sieves of metal wire cloth
