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 episode addresses the actions that should be taken to prevent the temperature to negatively affecting both processes and products.
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 chemicals involved must be marked by specific features according their intened use. What do we need to know about the subject?
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 several reasons: for example due to the presence of impurity within the ceramic raw materials or because of an improper use of defoamers.The episode try to offer a list of the most important causes, pointing out the mechanisms behind the problem, also providing some suggestions to prevent and/or eliminate it.
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 properly manage it?
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 keep in mind other production parameters, finding a balance or even good compromises.After a short definition of this amazing physical property, the episode offers a general overview on the issue.Not only in relation to tiles production.
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 with great attention, being subjected to several variables that can affect the final product.What are these variables? What mechanisms are behind them and what can be done to not compromise a good resolution?
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 actions that should be taken to properly solve production critical issues.How does the tool work and what are its most important functions to support ceramic industry?
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, highlighting its several properties and the benefits it promotes.With a focus on deflocculation of ceramic mixtures.
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 mostly produces by the use of digital glues and digital inks that, due to their particular chemism, can be considered the core of the problem.What do we need to know about it?
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 of its presence and what do we need to know to prevent its formation or to remove it in case of unexpected phenomena?
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 cathode-ray television sets and that may be visible even after the firing cycle.What is exactly the TV effect? How does it manifest itself and what are the causes?What can we finally do to prevent the problem?
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 - can sometimes rapidly and suddenly change, and grow.In the event of an excessive or out of standard increase, many critical issues may occur, compromising the use of the watery system or even forcing producers to repeatedly stop the production line.What are the main causes that can significantly affect the viscosity values of the slip and what do we need to know the proptly act, avoiding the worst-case scenarios?
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 sometimes be under the attack of significant bacterial proliferations.Microorganisms' activity (especially that of bacteria) is able to decrease or even nullify the action of chemicals that should provide suspensions with the right features to develop a proper application, also ensuring outstanding technical and aestethic results.In this perspective, what are the main consequences of bacterial degradations?
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 and complex, since it must strictly comply with specific parameters. What are digital inks? What are their components and their most important properties? The episode tries to give simple answers to those questions, offering a short identikit of this important category of products.
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 their rheological features during production. Sometimes drastically.What are the main elements that may affect, positively or negatively, the proper rheology of the barbottina and what do we need to know to prevent and avoid fluctuations, therefore preserving the proper features of suspensions?
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 all mechanisms that are the basis of the different rheological behavior on a microscopic and molecular scale.The episode offers an overview about the most important rheological behaviors of ceramic suspensions: barbottine, glaze and grit suspensions, engobes and inks.All these mixtures, in fact, in order to develop a good application and avoid serious problems along the production lines, must be marked by proper rheological features.Which ones?
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 episode offers a general overview about ceramic mixtures, focusing on the corrective action of some specific chemicals, able to develop and trigger an opposite process that provides the ceramic mixture with the proper features, restoring the parameters required for a good development of the process.With particular reference to the three major mechanisms underlying the deflocculation process:Electrostatic repulsion by cationic exchange2. Steric repulsion3. Complexation
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 happens inside the glaze and what can we do to prevent and to properly manage the problem?