Glazed Ceramic, Glazed and Polished Porcelain

What does it all mean?

Firstly, it’s important to understand that technically all tiles are Ceramic tiles. The terms Glazed Ceramic, Glazed Porcelain, Technical Porcelain, etc., are used in the industry and retail world to differentiate different types of Ceramic tiles.

So, what makes one Ceramic tile different from another? Let’s Talk Cake!

Cake

Picture an everyday sponge cake. In general, the ingredients to a sponge cake are flour, caster sugar and eggs – simple! So, the idea is to mix the correct quantity of ingredients, put it in a tin and cook it at the right temperature for the right amount of time to cook the ingredients, remove the majority of the water content and make the cake rise. Congratulations, you are now a master chef! Now, let’s say we want a cake that is not as moist, but of a denser consistency. We may add ingredients like baking soda, more eggs and butter, and cook it for longer at a higher temperature to remove more water. The basic ingredients indicate it’s still a sponge cake, but because of the added ingredients and the cooking process, we now have a different type of sponge cake – the same applies to Ceramic tiles.

The combination of clays and the addition of silicas and minerals, the pressing or moulding of the ingredients, and the time and temperature it’s fired at, gives us different types of Ceramic tiles.

Tile Definitions Explained

First thing’s first – it’s important to note that all tiles, whether they are ceramic, glazed porcelain, vitrified porcelain, etc., are all in fact ‘ceramic tiles’. The difference is in the production process in terms of how refined and pressed the base is, or what temperature the tile is fired at. These variations in the production process then determine the tile’s ability to be glazed (applying colour to the surface), or mechanically treated to create a textured, honed or polished finish.

Ceramic Monocottura/Monoporosa Ceramic Monocottura/Monoporosa

Both monocottura/monporosa tiles have been in existence for thousands of years and are versatile in any domestic bathroom, kitchen and main floor area. Both are single fired glazed tiles, however monoporosa tend to be wall tiles, with a softer glazing and higher water absorption levels, and monocottura tend to be floor tiles, with a harder glaze and lower water absorption.

Glazed Porcelain Glazed Porcelain

Glazed porcelain is ideal for indoor and outdoor applications. Glazed porcelains are dense tiles, therefore stronger and less water absorbent than ceramic monocottura and monoporosa tiles.

Double Loaded Porcelain Double Loaded Porcelain

These are an economical form of mechanically surfaced porcelain tiles. Generally, the surface is textured, matt, honed, semi-polished or polished. This tile is made by fusing two layers of varying clays together during the firing process. The decorative top layer is around 25% of the tile.

Technical Porcelain Technical Porcelain

Vitrified, or full body porcelain, does not have a glaze added to the surface – it is unglazed. Instead, it is the natural state of the raw materials, additives, and the firing process, that makes up the colour and pattern of the tile. One of the benefits of vitrified porcelain is that if the tile is chipped, the same colour is continued right the way through the tile, hiding the chip. Vitrified porcelain can be machined to produce a full polished, honed, or even rough textured surface on the face of the tile.

Water Absorption

The one important thing that both the cake and Ceramic tile share is water content. The more water in the cake, the more moist and soft it is. Of course, the opposite is true being the less water, the denser it is. With Ceramic tiles, the same applies and it’s this level of water content (or ability to absorb water) that gives us varying types of Ceramic tile.

Tile Water Absorption Diagram

Figure 1: Length of cooking time and degree of temperature effect on water absorption of tiles

Figure 1 above shows the basic difference between a Glazed Ceramic tile and a Porcelain tile. A Glazed Ceramic tile will have a higher water absorption rate (3%-6%), and is therefore a softer product, whereas a Porcelain tile must have less than 1% to be classed a true Porcelain tile and is therefore a harder and denser product.

A good way of explaining water absorption is this:  If you put a Ceramic glazed tile and a Porcelain tile in a bucket of water, the Ceramic glaze tile will weigh 3-6% more than its original dry weight, and the Porcelain tile will weigh less than 1% more.

Why is water absorption an issue?

There are a couple of basic reasons why water absorption is important. Firstly, the more water a tile can absorb, the greater the likelihood the tile will expand. Don’t forget that tiles are made of clay (dirt from the ground), and clay expands and contracts depending on water content. If a tile expands too much in a tiling system, the tiles can crack, pop up, etc. Now, before we all panic, 3%-6% water absorption is very minimal, so it is rare that damage will occur if the tiling system follows Australian Standards. These standards ensure correct glues are used, expansion joints are added, and grout widths are adhered to. Builders today are very good at ensuring these systems are followed. So, put simply, if a tile has the potential to absorb less water, it is less likely the tile will expand and contract.

Secondly, and probably the most important reason to understand water absorption, is that the water content of a tile determines what finish a tile can have on its surface. A basic Ceramic tile is a soft biscuit in comparison to a Porcelain tile, and so can only have a glaze applied to its surface. A Porcelain tile however, with its dense and stronger biscuit body, can also be glazed as a basic Ceramic, but more commonly it can be mechanically treated with diamond cutters to give a matt, honed, semi-polish or full polish surface.

Glazed Ceramic Tiles

Your basic Glazed Ceramic tiles are also known by many names, some common are Monocottura, Monoporosa or Bicottura. They are single (mono) or double (bio) fired tiles, generally at around 1000 degrees Celsius. Because of their softer ‘structural body’, also referred to as biscuit, a protective layer of engobe and glaze is applied to the tile surface, see Figure 2.

Glazed Ceramic Tile Layers Diagram

Figure 2: Glazed Ceramic Tile Layers

Engobe stops any water absorbed by the body of the biscuit travelling to the top surface layer. The glaze gives the tile its strong surface wearing properties and is what stops water and dirt absorbing into the tile’s surface and causing a stain. Glaze comes in virtually unlimited options, which is why you find basic ceramic tiles in thousands of textures, colours and gloss levels.

It’s important to note, Glazed Ceramic tiles have been around for thousands of years and have stood the test of time. For all intents and purposes, they are a hard wearing and economical covering, and still today, your basic ceramic tile is what makes up the majority of tiles used in residential housing throughout the world.

Rounded Edges (Cushion Edge)

From a construction process, Glazed Ceramic tiles are the most economical tiles to lay, as the softer biscuit tends to cut quite easily with manual tile cutters and basic tools. Sizes are commonly on the smaller side (up to 400mmx400mm), therefore alleviating the need to straighten walls or level floors, as the glues tend to capture these variations.

Another cost saving aspect to laying, is that Glazed Ceramic tiles tend to have rounded edges (see Figure 3). This helps the tiler get the levels between tiles as close as possible without having to be 100% perfect. The rounded edges are softer underfoot and combined with the grout lines, gives the tiler a bit of play and grace when laying tiles (see Figure 4).

Rounded edges on a tile

Figure 3: Rounded Edges

Rounded tile diagram

Figure 4

Porcelain Tiles

Like Glazed Ceramic, Porcelain tiles have also been in existence for many years. In the past, they were predominately used in commercial applications, because the resources and technology needed to produce this product came at quite an expense.

However, in the last 10 – 20 years there has been an increased availability of this product in both glazed (like Glazed Ceramic) and technical finishes (like Polished Porcelain, see Figure 5) as improvements in technology and process methods have resulted in lower production costs. The increased demand has resulted in a more economical product, while still being excellent quality, and exhibiting great product consistency.

Quality and output is much more consistent. What does this mean?

Lets’ go back to the cake for a second. Let’s say we are having a cake stall and want to make 10 cakes to sell. We can assume that by adding the same ingredient quantities to 10 tins and cooking the cakes all together at the same temperature and length of time, that we will get 10 identical cakes, right? Well, sometimes we do and sometimes we don’t. Why? It could be the combination and mix of ingredients, or the positioning of the cake in the oven. There are lots of things that can go wrong, and we may end up with some inferior cakes that we might not be able to sell, or have to sell at a discounted price. The same applies to Ceramic tiles. The basic setup to make Ceramic tiles means that if we make 10 tiles we may end up with 6 that are first quality and 4 that might be classed as seconds. With improved and smarter processes and technology, we can now produce a better product (porcelain), with higher first quality yield rates at an economical price. So, when we make 10 tiles we get 9 good quality, and that’s more tiles to sell!

So, Porcelain tiles are effectively ceramic tiles of a denser, stronger nature. Using a combination of varying clays, silicas and additives, extruded under extreme pressures and then fired at high temperatures, we get a ceramic tile that is far superior to a monocottura product. It has minimal water content and absorption properties and therefore cannot only have glaze added to its surface, but its surface can be mechanically treated to give us a honed, matt, semi-polished or high polished surface.

Double Loaded Porcelain - the surfaces are mechanically treated

Figure 5: Double Loaded Porcelain – the surfaces are mechanically treated. Pictured: Polished, External, Matt.

Technical Porcelain - This has a through body biscuit meaning the colour is similar to the surface glaze

Figure 5 (cont): Technical Porcelain – This has a through body biscuit meaning the colour is similar to the surface glaze

Technical Double Loaded and Technical Through Body Porcelain

Double Loaded and Technical Through Body Porcelain are the two most common forms of Technical Porcelain.

Double Loaded is simply an economical way of producing Technical Porcelain by applying two layers of Porcelain together – the top being the decorative colour. This top layer can then be mechanically treated, however if the tile is chipped/damaged beyond the top layer, you will see the bottom colour of the biscuit come through. For all intents and purposes, Double Loaded Porcelain is extremely strong and the most common form of Porcelain in the market. (See Figure 6)

Figure 6

Figure 6

Rectified Edges

More advanced Glazed tiles, and in particular Technical Porcelains, commonly come with ‘rectified edges’. Unlike Glazed Ceramic and entry level Glazed Porcelain tiles that have rounded edges for ease of getting levels right between tiles when laying, rectified edges are sharp with micro bevels (see Figure 7). This is a by-product of the Tile being cut to size after production, rather than the cookie cutter production methods entry level glaze products go through.

Rectified Edges with Micro Bevel

Figure 7: Rectified Edges with Micro Bevel

When working with rectified edges, tilers must take extreme care to get the level between tiles correct otherwise ‘tile lipping’ occurs and this can be felt underfoot (see Figure 8). It is also where dirt tends to get caught that is visible in natural lighting conditions, and can make a $100m² tile look like a $10m² tile if laid poorly.

Figure 8

Figure 8

Anti-Slip Systems

Slip Resistance can be very technical, but in simple terms, you must choose a tile that is suitable for the specified area, and in most cases, it is very logical. Slip Resistance comes into play when we are talking about tiles for balconies, patios, alfresco and even in shower bases.

With regards to tiles in shower bases, although there is no governance on this with residential applications, we strongly advise not to use high gloss Glazed Ceramic or Glazed Porcelain, or Technical tiles with a honed, semi or full polished surface.

Tip:  Slip Resistant tiles are harder to clean than non-slip internal tiles. Ideally use a hard bristle brush to scrub off dirt, then mop away with clean water or hose off if outside.

General Things To Know About Tiles

Laying Brick Bond

Oblong shape tiles, like 300mmx600mm, 400mmx800mm or even 600mmx1200mm, are generally made by cutting down larger tiles. This is more so with Technical Porcelain. When tiles are made, it is a natural characteristic for the tile to have some curvature or bow, that is where the centre of the tile is raised. (See Figure 9)

Figure 9

Figure 9

Because of this, when a tile is laid in a brick bond fashion, the middle of the tile does not line up with the ends of the other tiles. This unevenness is referred to as ‘lipping’ and can be felt underfoot or seen in natural light. (See Figure 10)

Tile lipping

Figure 10: Tile lipping

To avoid this lipping, we advise people not to tile in a brick bond fashion without checking that the curvature of the tile is minimal and therefore avoiding the variation. If, however, there is some curvature and the client wishes to have a brick bond effect, we recommended that tile is staggered only 200mm of the tile edge, rather than half (as per normal brick bond finish). By doing this, you can hide the curvature to a degree and still have that staggered look. (See Figure 11)

Brick Bond Tile Layouts

Figure 11: Brick Bond Tile Layouts

Batch/Shade Variations

An inherent property of tiles is batch or shade variation. Again, going back to our cakes, you are never going to get identical looking cakes out of one cooking period. The mix of clays and firing process in tile production means that within one run, we could end up with multiple batches or shades. Luckily, we have moved on from visual inspection of tiles to determine shade consistency. Advanced technology is able to sort out one from another pretty easily and our stock control systems mean that we will only send out one batch/shade per house lot, so there is no need to stress.

Batching and shade variations are inevitable in all tile products, and the tile you have chosen is indicative only to what you may receive. There may be no issue, or it may vary slightly, however it will still go well with your selection.

In saying this, some tiles are ‘designed’ with batch or shade variation to enhance the natural characteristics the tile is supposed to represent. There is a rating chart that governs this design variation (see Figure 12).

Tile variation ratings

Figure 12: Tile variation ratings

Trims and Angles

There are so many trims and angles available on the market to decorate and finish off tiles. The most commonly used are floor angles to finish off the edge of a tile where they meet a different substrate (like timber flooring), or square or round trims on wall tiles to hide the top edge of a wall tile (see Figure 13).

Figure 13

Cleaning Instructions

Please view our Tile Care section, or our Caring For Your Floors – Tiles Brochure.