Know Your Porcelain

Understanding the product is the key to design and specification

Porcelain tile is one of the fastest growing categories in the ceramic tile industry, especially in North America.? It has enjoyed such a meteoric rise in popularity that many consumers and designers are narrowing their choices to porcelain tile for every installation.? And, although there are many varieties of porcelain tile on the market, they all have different properties and it is often wrongly assumed that all porcelain tiles are identical.

The full range of porcelain tiles is somewhat complex.? Understanding the different terms that identify each composition simplifies the selection process.? It also ensures that appropriate tile is chosen for the job.? Understanding the origin of porcelain tile, that is, why it was developed in the first place, is key to knowing how to use it.? This also helps understand where, when and how it should be incorporated into the overall ceramic tile design.?

Certainly, some general concepts apply to all porcelain tiles.? A standard description would characterize it as having a dense impervious body, usually produced by the dust pressed method, and having extremely low porosity.? Twenty-five years ago at the inception of modern porcelain tile, the industry referred to one product only as porcelain tile, since only unglazed porcelain, general with a natural surface, was in production in the early years.? The original terminology required no additional defining adjectives other than salt & pepper (multi colored/granite) or solid (one color). The term porcelain was simple, easily understood, and the original product quickly established its value in commercial specification.

Porcelain in that early, unglazed form was conceived and developed to withstand demanding environments ? exterior applications, heavy-traffic floors, areas subjected to excessive water penetration or temperature fluctuations, and damage by chemicals or acids.? In order to create the unique inner microstructure of porcelain, high quality raw materials and specialized production techniques are required.? The pore structure is critical to achieving good color development, mechanical strength, and stain and frost resistance.? The design community particularly appreciated the extremely hard, unglazed tile?s natural deep abrasion and slip resistance.? Manufacturing tile for any specific use often meant enhancing certain attributes and sacrificing others to achieve the desired performance objectives.? Consequently, to achieve specific technical objectives, initial porcelain production suffered from a lack of aesthetics.? The unglazed surface, while durable and slip resistant, required a higher level of maintenance and its limited surface patterning hid soil poorly.

Polishing the unglazed tile was soon adopted into the process and the resulting high gloss finish added sophisticated textures to an otherwise limited design selection.? Unfortunately, surface polishing opens the closed-pore structure of the porcelain body and polished porcelains are more susceptible to staining because dirt get trapped in the surface pores.? For this reason, particular care must be taken when using a contrasting grout color with polished porcelain tile.? Sealants or other pre-surface treatments will reduce the problem, though.? While polished porcelain tile is extremely hard, it is still subject to scratching, line any other polished natural stone, and is best suited to walls and other areas that receive less wear and tear.

Over the past 20 years, many decorating techniques have been developed to add depth, pattern, texture and natural variation to unglazed porcelain tile.? All of these treatments are incorporated into the homogeneous body, maintaining the commercial benefits of each tile while improving its visual impact and increasing soil resistance.? Soluble salts, double loading and multi-pipe are just a few of the techniques now used to create natural veining effects.? Dry powder applications allow granules and flakes to be imbedded into the body, and micronized powder creates intricate travertine patterns.? Newer hammered and flamed surface textures heighten dimensional interest, closely mimic natural stone and enhance slip resistance.? Highly specialized glazes? applied to only the bas-relief areas of the tile are now recognized and applauded for their innovative approach in combining improved glaze aesthetics with deep abrasion resistance.? All of these decorative effects have increased the application range and added to the visual appeal of unglazed porcelain tile.

In the past five years, the compelling desire for richer patterns and more designs led to the introduction of glazed porcelain tile.? While the application of aesthetic glaze effects captured the interest of residential designers, it also created dramatic changes in the physical characteristics of the tile.? Particularly, it compromises natural slip and deep abrasion resistance and can reduce the tile?s resistance to chemicals and acids

Glazed porcelain also led to some confusion because it does not necessarily meet the performance requirements for challenging commercial applications and, therefore, it blurred the previously understood concept of what a porcelain tile was.? In glazed porcelain, the glaze hardness now determines a tile?s suitability to specific environments and use, and some glazed porcelain tiles should only be used in light or moderate traffic areas.? Thus, glazed porcelain tile intended for floor use must be carefully evaluated based on its PEI (Porcelain Enamel Institute) test classification.? In many cases, it should also be compared to other traditional ceramic-bodied tile.? And, unless frost resistance or water penetration control is a critical requirement, porcelain tile may actually add unnecessary material and installation costs to a project.

When selecting any of the various types of porcelain tile, it is also essential to specify the correct installation materials and methods.? By ISO definition, glazed and unglazed porcelain must not have more than 0.5 percent water absorption.? This low porosity presents a challenge to bonding and requires a premium two-part acrylic/latex enhanced mortar system.? To ensure the ANSI required 80-95 percent adhesion (interior, exterior or shower areas, respectively) back buttering is also strongly recommended.

Glazed surfaces are impervious to stains and provide easy maintenance so when glazed porcelain is selected to meet unusually harsh residential environments, it offers the combined benefits of reliable solutions and substantially increased design choices.? There is an extensive range of patterns, textures and colors and porcelain manufacturers are utilizing all their technological resources to create spectacular honed, antiqued and gloss/matte combinations.

Porcelain tiles perform differently and are not suitable for all environments.? Knowing why porcelain was developed in the first place should encourage us to questions its appropriateness for a particular application.? Given the tremendous variety of quality ceramic tile products on the market it is unnecessary to limit the options to porcelain.? No single tile is perfect for every job ? the key to selecting any type of tile for a project is to match the attributes of the tile to the desired aesthetics, performance, maintenance and budget.? Remember, there is a tile for every use and a use for every tile.

Because of its newfound popularity, porcelain manufacturers continue to develop new products and innovations.? Manufacturers specializing in unglazed porcelain and anchoring systems are focused on the virtually untapped potential for exterior cladding.? No other exterior surfacing material can parallel the properties inherent in porcelain tiles.