Also denominate as acrylic aldehyde (the simplest of unsaturated aldehyde), it is a liquid colorless chemical compound characterized by a pungent smell that reminds of burned fat.
The acrolein evaporates quickly, burns easily and is easily soluble in water, alcohol and numerous organic solvents.
If it is inhaled it may cause lung and respiratory damage, also causing eye irritation.
An aldehyde is an organic compound whose name derives from DEHYDrogenated ALcohol, which is one of its possibile methods of preparation.
The simplest compound of the aldehyde's family is methanal (better known as formaldehyde) which is often used as a preservative or bactericidal medium.
In the ceramic industry, the process eliminates the water content of the body prior to pressing.
Spray dryer machines are used for this, in order to obtain granules (hollow spheres) whose dimension is about 500 micron, and with a residual humidity about 7%.
The resulting granular product is proper to be pressed, creating the green tile.
Product able to create cohesion between inhomogeneous glazes where - specifically - water is not well blended with glaze's powder ("sand in water" effect).
Binding agents give homogeneity and consistency to the suspension.
A product containing substances or active principles which disinfect or prevent the degradation of a material. An active principleis a substance able to act against damaging organisms. The action of a biocide on such organisms will vary according to type: from ineffective, to abatement, to total elimination.
By chemism is meant the set of chemical characteristics of a compound or the phenomena caused by chemical actions.
A shining example not related to the ceramic world: by GASTRIC CHEMISM is meant both the gastric juice's chemical composition and the set of chemical phenomena of digestion that take place in the stomach.
COMBUSTION A chemical reaction in which a fuel is oxidised by an oxidant (normally atmospheric oxygen), generating heat and electromagnetic radiation (light).
Three components are required for combustion:
The fuel The oxidant Ignition
There are various types of fuel: hydrocarbons, wood or coal. Oxygen is nearly always the oxidant.
A chemical reaction in which a fuel is oxidised by an oxidant (normally atmospheric oxygen), generating heat and electromagnetic radiation (light).
Three components are required for combustion:
There are various types of fuel: hydrocarbons, wood or coal.
Oxygen is nearly always the oxidant.
The conductivity of a substance is its ability to transmit heat, electricity or sound. The SI unit of measurement is the Siemens per metre (S/m).
Reference values of the conductivity of water:
Ultrapure water = 5.5 – 10-6 S/m Potable water = 0.005 – 0.05 S/m Sea water = 5 S/m
Dark brown up to black colour area, which is visible in the internal part of the ceramic tile. Its presence is caused by an inadequate oxidation that nevertheless does not compromise the product functionality (unless it is accompanied by a swelling or pealing effect).
A substance that, if added to a colloidal system, prevents the flocculation (coagulation), changing the electrostatic set-up or the salvation or the surface tension of the colloid’s micelles. Ceramic slurries can include clay suspensions that tend to generate colloidal systems and flocculation problems: defloccualant agents prevent any flocculation process, also providing for a fluidised effect in the slurry itself.
Density: the ratio between the mass and the volume of a substance. In fluids, lower density bodies float over higher density bodies (as stated by Archimedes' Principle). The density of a body may vary with its temperature.
A digital ink is an ink for printing that is lied down with digital system like inkjet printers with piezo-elctric technology or digital printers with valve technology.
Process useful in separating two or more substances of a mixture and that exploiting the difference of their boiling points.
The distillation system can be used for the separation of complex mixtures or to purify individual substances. In any case, distillation involves the transition of a substance from a liquid to a gaseous state.
Following here the most significant transition processes:
SOLIDO / LIQUID = MELTING LIQUID / SOLID = SOLIDIFICATION
SOLID / GASEOUS = SUBLIMATION GASEOUS / SOLID = FROSTING
LIQUID / GASEOUS = EVAPORATION - DISTILLATION GASEOUS / LIQUID = CONDENSING
The word "engobe" derives from the French “engober”: to cover with a layer of soil. Chemically speaking, the composition of engobe is similar to that of a glaze (opaque and very refractory). The layer of engobe covering a raw ceramic body helps to isolate the ceramic mixture in terms of colour (the engobe creates the white base). At the same time, the engobe is formed so to chemically react to glaze during the firing process.
The flow limit is the minimum effort required to run a fluid.
When a suspension has a high flow limit, we do not see any sedimentation in the static phase.
A waterproofing material with a similar composition to that of glass. In the ceramic industry, the glaze, before the application on the green tile, is like a freshly ground mix of raw material and ceramic glass in a water suspension. The glaze suspension is applied on the green tile and, after the firing process, it finally becomes like glass. There are various types of glaze with different compositions, colours and finishes.
A ceramic tile or panel is called "green" prior to drying, so that it is characterised primarily by softness and flexibility.
In the ceramic field, the “sieve grinding residue” benchmark is used in order to measure the grain size of the ceramic mixture during the wet grinding process.
100 grams of slurry are manually sieved under flowing water untill the residual material on the sieve is constant.
That residue is dried in order to obtain a residue in g/100ml of slurry.
The sieves which are usually used can change from 45 to 75 micron, as the case.
Solvent that boils at high temperatures.
Chemically speaking, a high-boiling compound generally consists of complex, branched molecules with a high molecular weight.
Within a distillation process, the low boiling elements of a compound (like an ink) reach first their boiling point and therefore are the first to distill. On the other hand the high-boiling elements, if they even reach the boiling point during a specific process, go from a liquid to a gaseous state last.
In chemistry, the interphase is a real surface separating two different phases of a substance, i.e. the three-dimensional domain in which a substance transitions from one phase to another. The interphase is composed of molecules belonging to both phases.
A soap bubble is the most emblematic example of an interphase: its interphase is the layer of its spherical envelope composed of water and soap.
Atom or molecule that has a net electrical charge.
When an atom - or a molecule or a group of atoms bound together - gives up or acquires one or more electrons, it turns into ion.
The ions can have both a positive or negative charge: the first one are called CATIONS, the second ANIONS
Process according to which an aqueous suspension, such as a glaze, after being laid on the ceramic support, tends to distribute uniformly, reducing to a minimum the surface bumps.
LEVELLING AGENT In the ceramic tiles glazing process, a livelling agent is a product (usually liquid) that – if added to the glaze in water suspension – can improve the uniformity of the glaze itself (applied with double spray or dropping system).
In the ceramic tiles glazing process, a livelling agent is a product (usually liquid) that – if added to the glaze in water suspension – can improve the uniformity of the glaze itself (applied with double spray or dropping system).
The mechanical strength, also called the ultimate tensile stress, is the maximum stress to which a material can be subjected prior to failure.
The strength of a material depends on a variety of factors, from its quality to how it is kept, from the speed of application to the climatic conditions to which the material is subject.
In the ceramic industry, the mechanical strength is measured in a variety of ways: both in pre-firing (dry or green tiles) and at the end of production.
In physics, a mechanical tension is a force applied to a certain point of a surface. In the ceramic industry, mechanical tensions are forces which compromise the final technical performance of the product: from deformation to complete failure.
Solution formulated as a liquid base that can be mixed with inorganic powders (colored oxides, screen printing bases, vitreous grits, etc). It is useful for the creation of suspensions that have the ideal characteristics for specific applications (such as silkscreen printing, spray grits application, etc).
A "micella" is an aggregate of surfactant molecules dispersed in a liquid colloid.
A typical micelle in aqueous solution forms an aggregate with the hydrophilic "head" regions in contact with surrounding solvent, sequestering the hydrophobic single-tail regions in the micelle centre.
A measure of the acidity/alkalinity of a solution.
The pH is generally on a scale running from 0 (maximum acidity) to 14 (maximum alkalinity).
The following are common pH values:
- distilled water at 25°C (pH 7)
- human saliva (pH 6.5 / 7.5)
- vinegar (pH 2.9)
- Coca Cola (pH 2.5)
- hydrochloric acid (pH 0)
- alkaline soaps (pH 9 / 10)
- bleach (pH 12.5)
- sodium hydroxide (pH 14)
A polymer is a “macro-molecule” with a high molecular weight. It consists on a long chain that can present many branches.
The structure is formed by many “basic units”: these are single molecules, monomers, that can be described as pearls of a pearl necklace.
They may be aggregated in groups of two, three, four ….up to hundreds (high polymers).
Every monomer is linked to the others thanks to a chemical bonding: the polymer can be depolymerised using solvents able to break the chains.
In the ceramic industry, a primer is a product that, if applied before the digital ink jet decoration, allows to manage at the best the decoration itself. Some of them improve the definition printing, some others allow to standardise the ink absorption on the top of the surface; others increase the inks drying time (for inkjet adhesives, for example).
Study of the flow of matter in response to an applied force. It is a branch of physics which deals with the deformation and flow of materials, both solids and liquids.
The rheological analysis is important (in the ceramic production process or not) every time we need to analyze the behavior of a fluid or, more frequently, if we want to manage and determine its behavior. A glaze's spray application, for example, must have a very low viscosity when the flow speed is high. For the same reason, the viscosity has to be greater when the flow speed is zero (flow limit). That also makes that the glaze does not settle when is at rest and is not moved.
In the ceramic field is important to check and verify the rheological attitude of clay's grinding process with fluidifyng agents that can avoid a gelling process before and after the mill' discharge.
Rheological parameters are usually measured by using viscometers and rheometers.
We all have daily contacts with rheology, even if it happens unbeknownst to us. We are in fact able to define - at least empirically - the characteristics of a product, defining it on a case-by-case basis as flexible, rigid, viscous, creamy, gelatinous, etc...
In order to carry out their actions correctly, many common products must have specific rheological properties.
Process that occurs in a heterogeneous mixture consisting of particles suspended in a liquid. It consists specifically in the separation of these particles from the solution with the formation of a sediment that arises due to gravity or other forces such as centrifugal force.
Sequestrant agents are widely used in chemical practice to eliminate interfering ions in reaction or analysis environments, thus isolating otherwise unstable species.
The most common are those used in the field of detergent. Their use is useful, for example, to make the soaps less sensitive to the action of hard water, in the treatment of industrial waters, to preserve medicine and food.
Sintering is a process of compacting and forming a solid mass of material by heat or pressure without melting it to the point of liquefaction.
It is used to create material with specific features that would not be effective if created with a different system.
It is a densification process that at the same time provide a significant decrease of the porosity in the interstices.
A viscous mixture of water, clay and other typical raw material which usually form the ceramic mixture.
Depending on the proportions of the mixture and on the use of specific fluidifying agents, the slurry will have different consistency and density.
The softening point is defined as the thermodynamic state in which a material without a defined melting point begins to modify its own state of aggregation from solid to fluid.
Contrary to popular belief, glass is not a solid but a "sub cooled fluid" and has a softening point which corresponds to temperature and pressure conditions at which glass collapse on itself. A different softening point corresponds to a different type of glass.
A solvent is a fluid that dissolves a solid, liquid or gas (the solute), thus forming a solution.
Being chemically inert, solvents should not react cehmically with the solute (the solute is the compound which forms a solution with the solvent).
Solvents may be of two types: POLAR and APOLAR.
The polar/apolar nature of a solvent determines which compounds it can dissolve and with which other solvents it can be mixed.
A property of solids defined as the total surface area of a material per unit of mass or solid or bulk volume.
In the simplest terms, surface tension is the force that holds together the two sides of a hypothetical cut perpendicular to the surface of a fluid. It is the tension that, for instance, stops very light objects penetrating the surface of water (leaves, insects, etc.).
A mixture of two substances, a fluid and a solid, characterised by the very long time required for the sedimentation of the solid component. In solutions, the two components are not distributed and mixed evenly.
A substance that promotes the uniform dispersal in water of a substance. Suspension promoters are used in glaze and slip to prevent the sedimentation of their solid components.
Tensio-active agents modify the surface tension of a fluid.
When dissolved in water, they form aqueous solutions with a lower surface tension than water itself.
Tensio-active additives, for example, are used to stop a glaze and a solvent base ink repelling each other.
Thixotropia is the properties of some pseudo-plastic fluids to change their aerial condition under cut solicitations or if subjected to peristaltic actions (after a long calm period).
In these circumstances the fluid can move from an almost solid to a liquid state. In general from a gelatinous to a liquid state. The slurry has often that kind of proprierties.
A trace element is a chemical element whose concentration (or other measure of amount) is very low (a "trace amount").
In analytical chemistry, a trace element is one whose average concentration is less than 100 parts per million (ppm) measured in the atomic count or less than 100 micrograms per gram.
Viscosity (or viscous friction coefficient) measures a substance's attitude on generating friction between its layers. In other word it defines the flow resistance of a fluid.
In liquids, the coefficient of viscosity is inversely proportional to the temperature: the more the temperature increases the more the viscosity decreases.
Wetting (or wetness) is the ability of a liquid to maintain contact with a solid surface.
Wetting deals with the three phases of materials: gas, liquid and solid.
For water, a wettable surface may be termed hydrophilic and a nonwettable surface hydrophobic. That can be measured with the “contact angles” test.
Super hydrophilic, which literally means ”strong affinity for water”, gives maximum wetness to the surface.
On the other side, in the case of super hydrophobic circumstance, wetness is totally absent, facilitating the presence of single and isolated drops.
All wetting agent create the condition to obtain the wetting of the substrate.