Apparently invisible. Chemistry in ceramics.

At present, in the heavy clay industry, products are decorated mainly by applying engobe with the aid of scattered granules or by means of reduction effects created by the firing process. These techniques are suitable to produce traditional products for the existing market.  What added value does digital printing offer in this field?

The operating temperature is an important parameter that ceramic producers must take into account in order to avoid application problems that can also negatively affect the quality of the finished product. However, this parameter is not always easy to manage, especially if we consider the fluctuations promoted by seasonability. The episode addresses the topic with the help of specific examples, hi...

Most ceramic production processes involve the dispersion of ceramic powders in a liquid medium - mostly water - to obtain a suspension or, more generally, a dispersed system. To provde the suspensions with the desired stability and workability, depending on the different applications, we use the addition of small quantities of suitable chemicals that, interacting with the solid particles, change t...

All analysis of ceramic suspensions carried out by those companies that supply chemicals for ceramic production are fundamental to properly develop the processes that take place along the production line. The episode provides an overview about the role of these important investigations, with a focus on the data and on the operations of the involved tools. We will talk about jars, pycnometers, lase...

After addresing the impact that seasonality can have on the the fluidization of ceramic mixtures and on bacterial proliferation within semi-finished products, this second part of the episode 41 tries to show and explain the consequences that temperature changes may produce on the drying time of ceramic suspension, leading to alterations that often force producers to revise the parameters of the gl...

In ceramics, the use of chemicals plays a fundamental role in providing the final product with high technical and aesthetic results and in promoting a proper application process. However, their actions can be sometimes less effective or compromised.  There are several reasons for this performance change and seasonality is surely one of the most interesting. Through a series of examples, the episod...

Glaze and grit suspensions are made up of a liquid part (usually made-up of water and one or more rheological chemicals) and a dispersed solid part. However, these two different suspensions show a lot of differences that may lead to very contrasting results, also implying a different approach about chemicals, both during the grinding phase and along the glazing line. From this point of view, all c...

Cratering phenomena are defects that appear as microscopic craters on the surface of ceramic bodies on which an aqueous (and still drying) suspension has been discharged. It is an application problem that leads to a misalignment of the suspension due to the presence of one or more dips. The problem, that is already visible along the glazing line and not only after the firing process, may arise for...

CMC are organic compounds, water-soluble polymers derived from cellulose, widely used in several fields of industrial production. In ceramics, sodium CMCs perform multiple functions within suspensions and solutions and can be marked by very different properties depending on the situation. What is the main role of this substance in the ceramic production process, and what needs to be done to proper...

The plasticity values of ceramic mixtures is a very important issue, since it affects the values and features of the mix and therefore the proper development of the ceramic production process. In general, the use of clays marked by high plasticity values is usually synonymous with easier process management. However, high-performing clays are not always available and it is therefore important to ke...

In ceramics, digital technology (use of digital glues and digital inks) has definitely riform the sector, making the production process much more flexible and expanding creative and aesthetic possibilities. The extraordinary precision with which the ink is discharged on the ceramic support, in fact, has opend to new extraordinary results. However, the topic "printing definition" must be addressed...

Scanning Electron Microscope is a sophisticated tool used in many fields of scientific research, even in ceramics. The use of an electron beam instead of light allows to get not only outstanding high resolution images but also detailed information on the composition of the sample. Insights are so accurate and exhaustive that offer manufacturers clear solutions or, at least, suggestions about the a...

Sodium silicate is an inorganic substance that at room temperature it is in solid state. It is a chemical compound used in several areas of industrial production. In ceramics, sodium silicate is very effective within ceramic mixtures. Among the several effects it produces, it plays a very important role in terms of fluidization. The episode is about the function that this substance performs, highl...

Polluting and odor emissions are two important critical issues that producers have been looking for some time with considerable attention. This is a problem that appears in the final stage of the ceramic production cycle, inside the kilns, but whose origin can be found in the previous application processes that mostly take place along the glazing line. Scenarios can be different but emissions are...

Among the several issues that may arise along the glazing line, the excessive foaming within glaze suspensions is one of the most frequent and problematic. The phenomenon is already visible on the surface of the glaze inside the stirring systems but consequences can persist even after the end of the production, that is after the firing cycle. Chemistry speaking, what is foam? What are the causes o...

Speaking of ceramic glaze applications and technical defects, one of the strangest and most interesting is the "TV effect". It consists of a preferential migration of the glaze towards the perimeters of the tile that produces in those areas a thickening of the glaze. The unaesthetic result is a quite regular surface swelling along the edge of the ceramic material.  A result that recalls the old ca...

Viscosity (or viscous friction coefficient) measures a substance attitude on generating friction between its layers. In other words, it defines the resistance of the fluid to its proper flow. The barbottina's viscosity values - that is the suspension of inorganic raw materials, water and dispersants that after the atomization process will form under the weight of the presses the raw ceramic body -...

All process water involved in ceramic production, both tap and well waters, usually contains bacteria. And the same applies to inorganic raw materials used in the grinding process to produce the semi-finished products that will later be applied along the glazing line: frits, clays, feldspar, nepheline, etc.  Because of the huge amount of water use, glazes and engobes grinding departments can somet...

Thanks to the digitalization of some of its processes, the ceramic industry has evolved pretty significantly over the last few years, and in this perspective the digital printing system plays one of the most important roles. In fact, the use of digital inks has made it possible to almost totally replace the old decoration systems. Their formulation and therefore their production is very delicate a...

In general, wet grinding systems offer best performances and best production results only when the chemical and physical features of slips are constant over the duration of the entire process. More precisely, this happens when the main parameters of the atomized product (such as grain size, density, viscosity, and thixotropy) remain within a very short range. However, slurries may suddenly change...

Formaldehyde, despite its wide use in many fields of the industrial production, in high percentage may be a serious problem. In Ceramics, it must be carefully checked since it can seriously and negatively affect the environment. What do we need to know about this topic?

Rheology is the science that deals with the flow and the strain rate of matter. It’s a branch of Physics that studies the origin, the nature and the deformation’s characteristics of a matter under the influence of external forces, with particular regard to non-Newtonian liquids. Its main goal is to define the correlations between causes (forces) and effects (deformations and flows), identifying al...

The episode focuses on the flocculation phenomena of ceramic mixtures. The problem is marked by a progressive aggregation of solid particles and it often takes place due to phenomena of electrostatic attraction between the clay micelles in suspension. This process leads to a significant increase in viscosity within the system, negatively affecting the proper development of the production process....

The lack of cohesion that occurs not only between the glaze’s particles but also between the glaze and the raw ceramic support can lead to a problem commonly called "dusting phenomenon". This kind of glaze, that we could define as fragile, is easily removable from the ceramic surface, especially when it undergoes to the mechanical solicitations that take place along the production line. What happe...