|Monthly Tech-Tip |
A set of numbers representing the percentage of dry material particles retained on each sieve in a stack of interlocked sieves with successively finer openings. The stack of sieves is vibrated in a shaker until all material has filtered down through. The test should specify maximum water content of powder, shaking time, settings for shaker (if appropriate), and what sieve series was used (i.e. US Standard, Tyler). Should also specify whether numbers refer to % on the sieve or % passing the sieve.
For a more detailed test see SIEV. It is our opinion that a water washing test is more effective and accurate.
To measure particle size in a slurry or powder you need sieves. This is the most popular type used in labs. They are made from brass by a company named Tyler. The range of screen sizes for testing particle size is very wide (obvious here: the top screen has an opening of 56 mm, the bottom one 0.1 mm - the wires are almost too small to see). You can buy these on ebay for a lot less than new ones, search for "tyler sieve". The finer sieves (especially 200) are fragile and easily ripped. It is good to have a 50, 100 and 150.
These particles are from a grog that has been milled and separated into its constituent sizes in the lab. As you can see it has a wide range of particle sizes, from 48 to finer than 200 mesh. When fired ceramic (like bricks) is ground the finer sizes often predominate. Because the coarser grades have a lower yield they can be much more expensive and harder to get. But they are the most effective in reducing the drying shrinkage and fired stability of structural and sculptural bodies.
The Physics of Clay Bodies
Learn to test your clay bodies and recording the results in an organized way and understanding the purpose of each test and how to relate its results to changes that need to be made in process and recipe.
Particle Size Distribution
Knowing the distribution of particle sizes in a ceramic material is often very important in assessing its function and suitability for an application.
Sieves are important in ceramics for removing particulates and agglomerates from glaze, engobe and body slurries.
Tests conducted on bodies made from materials, as opposed to the materials themselves.
Tests conducted to determine particle populations, sizes, shapes, densities, surface areas, etc.
|Tests||Ultimate Particle Size Distribution|
|Tests||Sieve Analysis 35-325 Wet|
|Tests||Average Particle Size (Microns)|
|Tests||% Passing 325 Mesh Wet|