Performance Glaze MaterialsFor fine ceramic glazes

improve glaze quality with reduced surface defects

Performance materials for improved glaze aesthetics

Sibelco has a wide range of specialist colourants, additives and specialist materials which are formulated to give exceptional performance in glaze applications.

For the manufacture of fine ceramic glazes where surface finish and aesthetics form a key attribute of the final customer product quality.

Sibelco Europe Minerals Plus supplies Casiflux® and Tital® which are derivatives of calcium and magnesium respectively and can be added efficiently to glaze formulations as high performance silicate minerals to improve surface aesthetics.

The key features of the range are:

• Low colouring oxides• Improved sintering• Reduced CO2 evolution• Finely micronized for direct glaze batch addition

Recommended glaze applicationsProduct Sanitaryware Tableware Tile

Casiflux

Tital

The Casiflux® range of products are produced from carefully selected wollastonite, a naturally occurring calcium silicate mineral. The chemical composition of raw materials and product is closely monitored. Variation in chemical composition and particle size distribution of Casiflux G is kept to a minimum. Casiflux G is produced in 2 grades ground to optimise glaze and ceramic performance.

The Tital® range of products is produced from carefully selected high purity talc, which is a natural hydrated magnesium silicate. Using our proprietary micronization technology we process the raw material to various particle size distributions. Properties of the product are closely monitored and variation in chemical composition, whiteness and particle size distribution is kept to a minimum. The products are low in iron content and have a high brightness. Tital 4591 can be used to introduce magnesium into ceramic bodies and glazes

Chemical and Analytical Data - Typical values which do not represent a specification

UnitCasiFlux

G20CasiFlux

G38Tital

4591

CaO Mass % 44 0.18

SiO2

Mass % 52 60.4

K2O Mass % 0.1 -

MgO Mass % 1.2 33.4

Al2O

3Mass % 0.45 0.04

Fe2O

3Mass % 0.37 0.25

Loss on ignition Mass % 1.7 5.5

Benefits of using Casiflux & Tital in Fine Ceramic Glaze ApplicationsReduced glaze defects from gas evolutionGlaze surface defects such as pinholes are generally caused by trapped gases generated during the melting phases by the decomposition of raw materials. for example; When calcium and magnesium carbonates are heated they liberate carbon dioxide.

CaCO3 CaO + CO2

MgCO3 MgO + CO2

CaMg(CO3)2 CaO + MgO + 2CO2

In theory, the temperature at which this happens is ~950°C, well below the fusion point of a typical sanitaryware glaze. However, in practice some the gas generated gets trapped within the glaze as it starts to sinter at lower temperatures, causing bubbles. If these bubbles are allowed to reach the surface of the glaze during the firing process then glaze defects such as pinholes or even blisters can appear.

By reformulating glazes to use Casiflux G38 and Tital 4591, the problems associated with glaze bubble can be significantly reduced.• By replacing calcite, dolomite and quartz with Casiflux and Tital, less gases are formed when the glaze fuses and melts.• The liberated gases tend to form on undissolved particles of glaze (e.g. quartz or zircon). Casiflux and Tital will melt without leaving

residual particles to which any gases may adhere. • When compared with a glaze formulated with calcite and dolomite, a Casiflux/Tital glaze will start to fuse at a higher temperature,

giving any evolved gases more time to escape.

Figure 1 – Typical sanitaryware glaze formulation and modfications using Casiflux and Tital

Formulations Base kg 1 kg 2 kg

Dolomite 49 49 -

Feldspar 466 466 466

Quartz 218 132 94

Kaolin 86 86 86

Zircon 162 162 162

Casiflux G38 - 165 197

Calcite 137 - -

Tital 4591 - - 35

Binder 3 3 3

Raw glaze 1,121 1,063 1,043

Total Fired Glaze batch (kg)

1,000 1,000 1,000

* formulation to achieve 1,000 kg fired glaze

As direct replacements i.e. keeping the same glaze chemistry (figure 1); not only is the incidence of bubbles reduced (figure 3), but there are the added benefits of a slightly higher sintering/vitrification point, allowing more time during the firing process for gas to escape from the body below the glaze and increased glaze flow at peak temperature (figure 2) making the glaze more forgiving of application faults left on the surface prior to firing or possibly allowing for a reduction in feldspar or frit to produce the same flow.

Figure 2 – Flow of sanitaryware glaze surface

Results Base 1 2

Fusion Point 1100°C 1125°C 1125°C

Flow - +18% +19%

Figure 3 – Cross section of sanitaryware glaze surface

Base Formulation 1 CasiFlux 2 CasifFlux & Tital

www.sibelcoceramics.come-mail: qualityceramics@sibelco.com

over 220 production sitesin more than 40 countries

mineralsplus.sibelco.com