Apparently invisible. Chemistry in ceramics.

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?