Publication Info.

The History of Ceramic Tile in the United States

Presented by Robert E. Daniels, Executive Director Emeritus of TCNA (Updated September 2005)

When I was asked to write a history of ceramic tile in the United States I took a long time thinking about how to approach the subject. Ceramic tile has a long history. Probably no one knows the actual beginning but tile has been around for a very long time. I remember how impressed I was with the tile still in good condition in the ruins of ancient Rome. The tile in Pompeii is still in excellent shape after 2000 years, although it was buried in volcanic ash for much of this time.

Recently a kiln was unearthed in Centamura del Chianti, near Siena, Italy from the 3rd century b.c.e. Broken pieces of ceramics were found in the ruins of the kiln. These were surmised to have been offered to the god of the kiln to bless the outcome of future firings. Making ceramics was a hazardous and speculative business in those days. But this article is about the more recent past where the outcome of the firings is much more predictable.

North American tile making had its roots in Europe where tile had been manufactured for years. Tile artisans brought this craft with them in the 1800's and set up tile making factories all over the country. Tile was largely made by "batch firing" the tile in some form of stationery kiln, such as a beehive shaped brick kiln. The tiles were placed into the kiln and heated or baked until some transformation of the mineral particles occurred. This would cause the body to solidify and, if glazed, for the glaze to melt and fuse to the body of the tile. The process could take 24 hours or more for this single firing.

In the pre-World War II era, much of the tile was made in this batch fashion. The tile body material was fed into a press usually by hand, then dried, glazed and baked in a batch kiln. Loading and unloading kilns was a major labor-consuming item. Finishing was laborious as well and could involve hand painting tiles, silk screening, inserting different colored glazes and other forms of decoration. If a multi-colored tile was to be produced multiple firings would be required. Thus the tile would have to be hand-loaded in and out of the kiln and heated for many cycles before it was completed. This could take many days for completion of a production run. The amount of labor was very high.

The firing temperature in these batch kilns could vary quite a lot from one area of the kiln to another resulting in size and color variations as well as a high scrap rate. Thus the yield of a given run could be quite low.

One major improvement from these early method was the development of the tunnel kiln, a long structure that had moving transport devices conveying tile through continuously. The tiles ready for firing were loaded onto carts with support devices called "kiln furniture" and the carts pushed through the kiln by some means including human-power. It took a strong back to push kiln carts through a 200-foot or longer kiln. Other innovations in the early 1900's included the use of conveyor belts to transport the tile from the press to the finishing department and into the kiln and mechanical presses to take the human muscle out of the process.

But the industry didn't stop there and is still innovating. In the 1960's early experimenting with a device called a "roller-hearth" kiln began. The device consisted of a series of ceramic rollers that were gear-driven and would transport a single layer of tiles through the firing zone of a kiln. This method had several advantages. Each tile was exposed to a very similar firing condition making the tiles more uniform. Also the firing time was reduced to less than 45 minutes and finally, the tiles could be automatically fed into and out of the kiln.

By the early 1980's roller-hearth kilns were being installed in the United States. This was a sea change for our industry. Other innovations from this period included hydraulic presses that could generate very high pressure allowing for larger-sized tiles, greater body uniformity, and more output per stroke of the press.

The output of the earliest production roller-hearth kilns was about 6-7 million square feet per year. Today there are large kilns that will make 30 million square feet per year with the same number of workers. The process that is used for most tile production today is known as the pressed-dust method. It involves grinding the mineral constituents of the tile body in water slurry. The tile body is made up of a mixture of various mineral components depending on the desired properties of the finished tile, such as feldspar, ball-clay, talc, shale, etc. ground to a various particle sizes.

This slurry, which contains about 50% water is then spray-dried to a damp powder and stored to season it. From storage the powder is fed to the large presses, some exerting up to 7 tons of pressure, where it is pressed into the shape of the tile body. The next step is to convey the tiles into a drier to reduce the water content to about 2% and then to the glazing line (some tiles are not glazed) where a plethora of devices may be used to create the desired look. Some devices include sprayers, silk-screening devices, dry-glaze dispersers, waterfalls, rollers, texture imprinters etc.

From the glaze line the tiles enter the kiln where they may be fired once (monocottura) or several times if required by a specific design, Then the tiles are transported directly to an inspection area where a visual and/or electronic inspection of every tile occurs. The latest technology provides for complete computer testing for size, shape, flatness, and finish. Tiles are automatically sorted to a tolerance of ½ millimeter size and placed into appropriate caliber stacks and then put into marked cartons. Most of these steps take place with no human intervention in the latest technology driven factory.

At the end of the line, a robot places the cartons of tile on a pallet for movement into the warehouse. This is not to say that there are no workers in the plant. With all this high tech equipment the factory needs a highly trained and capable maintenance department. Unfortunately most plants have to contend with kiln fires, broken rollers, and other mishaps. Since the process is continuous for 24 hours a day 7 days a week, the crews must be ready at all times. Changeovers are required for the various colors, sizes of tiles, and textures. Ceramic engineers and technicians must be on hand to develop formulations and techniques for the different designs. The production managers would love to run all off-white 12X12 inch tiles all the time but today's educated consumer wants variety.

Interestingly enough, despite all this technology there are still tile producers making hand-painted and formed tile that is batch-fired in the old way (except they are using small electric kilns instead of the old brick beehives). The Tile Council of North America has about 50 art tile makers using some of the techniques of yesteryear mentioned above.

What does this mean for the consumer? For one thing the reduction in labor has made ceramic tile very affordable. The price has never been lower in the current period. Tile is available in many sizes, designs, styles, textures, and colors thus freeing the designer to create a given look. Modern techniques permit the manufacturer to make tile that emulates natural products such as marble, limestone, granite, slate, etc. Tile that matches older styles is available for the period look. The properties of tile such as strength, shape, size tolerance, slip-resistance, color, shading, are much more uniform and predictable. New equipment can make individual tile that are 2X4 feet or larger.

In short we've come a long way since the days of the ancients and we are still going forward.