We explain what sieving is in the separation of mixtures, what types of sieves exist, their characteristics and some examples.
What is sieving?
Sieving (or screening) is a simple method that allows particles of different sizes to be separated by passing them through a sieve (a wire mesh filter) or fine strainer. During this process, small particles pass through the holes in the strainer and larger particles are retained.
The same solid element, solids combined with each other or solids combined with a liquid can be sieved, but it is not possible to use a sieve to separate different liquid substances.
Sifting was practiced in ancient times, for example, to separate flour from remains of straw, insects, corn husks or seeds. Currently commercial flour is refined, so it is not necessary to separate it from impurities or unwanted substances. However, it is sieved to eliminate lumps or lumps produced by ambient humidity.
See also: Methods for separating mixtures
Types of sieves
The main types of sieves can be:
- For home use Its main use is to sift flours and starches to achieve masses with a softer, more airy and homogeneous consistency, without lumps.
- For industrial use It can be a granulometer (for grains), a stationary grate (for handling coarse solids) or a rotating sieve (continuously separates solids that are suspended in a liquid).
Sieve characteristics
The sieves can be of different shapes and can be made with very different materials. For example, they can be metal cylinders with a wire mesh at their base, round and wooden with a weave of rods or fabric at the bottom, wooden in the form of a frame with a mesh fabric, bowl-shaped made of plastic or silicone, among others.
The interlacing of the mesh or wire fabric consists of a weft (a set of crossed and intertwined threads) and the mesh opening (the useful opening through which the smallest particles of the substance to be sifted pass).
In the professional field, such as laboratories or the chemical industry, the sieving process It is very important to define the quality of the final products. In the construction field, the sieving process is also carried out to separate sand from larger particles (such as stones), especially to prepare the mixture for wall plaster.
Examples of sieving
Some examples of sifting are:
- The flour Sifted, it is much lighter and allows it to be mixed better with other ingredients (avoiding the formation of lumps or lumps).
- sifted flour with other dry ingredients like cocoa powder, helps combine them with the rest of the ingredients more evenly.
- The grains Sifted foods, such as rice or quinoa, can be separated from stones, impurities, or broken grains.
- The metals precious (like sifted gold nuggets), can be separated from the sand and earth with which they are always mixed.
- coffee beans They are sieved to separate them from toothpicks and leaf remains.
Continue with: Filtration
References
- «Sifting» in Cambridge Dictionary.
- «Is sifting flour for baked goods really necessary?» at TheKitchn.
- “Sieve” on Wikipedia.
- «Sifted» on Slideshare.
- «Types of sieves» in Mym Technical Instruments.
- «Different Sieving Methods for Varying Applications» in AZOmaterials.
