Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Why do we shake the saltcellar before sprinkling the salt?

If our food is a bit dull, the reaction is automatic - we take the saltcellar and we shake salt onto it. We have learned this from a young age: you have to shake the saltcellar so that salt comes out. Why is this?

Salt, as with rice, cement, sand, are finely divided solids which we call granular media. They are groups of similar particles that can behave as a liquid, flowing through orifices; or as a solid, given that they can maintain a constant shape and volume (see Fig A, sand sculptures). This is why the behaviour of granular media is curious and, on many occasions, problematic.

Figures A, B, C and D

One of the intrinsic phenomena on handling granular media is the spontaneous formation of arches as shown in figure B. Arches are structures as used in architecture in order to construct bridges and aqueducts (figure C). These arches are referred to as being vaulted when formed in three dimensions and have the common feature that the particles forming them stabilize each other. That is, if one of the arcs making up the vaulted arch is eliminated, the whole structure will collapse.

When a granular medium flows through an orifice, the formation of the vaulting can cause a blockage. The flow of particles stops and the arch supports the weight of all the material on top of it, in the same way that the arches of a bridge support the weight of the vehicles crossing over it. The blockages in the flow of a granular medium cause serious problems in certain industrial processes. The plastics, cement and pharmaceutical industries are example of where granular media are the main players.

The blockages in discharging silos or dosifiers have physical properties in common with other kinds of hold-ups. Who has not been in a traffic jam, with the start of their holiday delayed? An example closer to home – and certainly more dangerous – is that of the bull running in the fiestas of San Fermín in Pamplona (figure D). When the street narrows and the runners run into each other, a spectacular accumulation of bodies occurs.

Over the past decade numerous scientists have been trying to understand the properties of obstructions of this nature, as well as the factors that are most influential in their formation. Nevertheless, there are many questions left unanswered. In this thesis Iker Zuriguel has investigated the simplest example of blockages that can be studied in the laboratory: a small silo full of spherical particles and with a circular orifice at its base. The thesis was presented at the University of Navarra.

Despite the apparent simplicity of the phenomenon, the unresolved questions are many. For example, what controls the phenomenon of blockages? The particle size? The size of the orifice? This thesis shows that the really important factor is the relationship between the radius of the orifice and that of the particle. Another important question: with the same size of particle and orifice, is it always the same number of grains that fall in an avalanche before the system blocks up? This research is a resounding proof that this is not so. For the same experimental conditions, we can find avalanches of 10 to 10,000 spheres!

The most important result of this thesis was the discovery that, in a 3-dimensional silo, when spherical particles are used, it suffices for the radius of the orifice to be five times greater than that of the particles in order that obstruction does not occur. And, as the saltcellar has holes less than this size, it is necessary to shake it in order to break up the arches formed and that impede the salt to free-flow on to our food.

Irati Kortabitarte | alfa
Further information:

More articles from Physics and Astronomy:

nachricht Move over, lasers: Scientists can now create holograms from neutrons, too
21.10.2016 | National Institute of Standards and Technology (NIST)

nachricht Finding the lightest superdeformed triaxial atomic nucleus
20.10.2016 | The Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Resolving the mystery of preeclampsia

21.10.2016 | Health and Medicine

Stanford researchers create new special-purpose computer that may someday save us billions

21.10.2016 | Information Technology

From ancient fossils to future cars

21.10.2016 | Materials Sciences

More VideoLinks >>>