Principle - Third fire decoration has grown enormously over the past few years, developing from an artistic and craft activity to a real industrial operation.
Although the batches produced are much smaller than those of conventional industrial tile production, the quantities of tiles decorated in this way are nonetheless high enough to justify the use of plant purposely built with state-of-the-art production lines.
The principle is to apply decorations into glazed tiles on which an initial layer of glaze has already been fired.
The term "third-fire" derives from the fact that the technique was first used when double firing was the only production process.
In order to decorate a product with a fired layer of glaze (after the product had already been fired twice), it had to be fired a third time to fix the decoration.
The term is now used to describe decoration of a product that has already completed the normal production process.
Printing on an impermeable and nonabsorbent, vitreous surface is more complicated than printing on a porous surface such as unfired glaze. Nonetheless, this procedure has some positive aspects that make it useful for application on ceramic tiles.
Decoration can be performed using any of the methods we have described, provided that the characteristics of the inks are modified to take account of the fact that the tile is unable to absorb the liquid part of the ink.
For third-fire decoration, the most widely used technique is still flat screen-printing, both for application of screen printing inks and for dry applications (e.g. powders, frits). Sometimes the decorations are performed by hand (freehand, using stencils, etc.)

Printing Characteristics - The aim of third firing is to produce high-value tiles, which can be used in small quantities to enhance the visual appeal of the floor or wall tile installation.
It is most important that the decorated tiles coordinate successfully with the field tiles. Since it is difficult to guarantee the same colour tones in tiles from different production and firing cycles, decorating selected fired products is an effective way of ensuring that the background colour is identical.
The fired tiles are also dimensionally stable, which eliminates a further cause of variability in the finished product.
This procedure is characterized by small batch sizes. The plants are designed and sized for exceedingly high flexibility and tile type can be changed several times a day.
Often it is not just the colour and/or design that is changed but also the tile size or the printing procedure.
Products often undergo screen-printing, partial manual decoration, and pointed application.
Given that the purpose of this process is to increase the value of standard products, in most cases, a large number of applications (six or more) are used.
The high value of the product makes it necessary to do everything to achieve the highest possible quality, while output is of only secondary importance.
Due to the plants flexibility and the lesser importance of quantity, in the plant management economics, tile manufacturers tend to use third fire decoration for articles that require a lower production speed than is optimal for large-scale lines.
Mass-produced products are therefore manufactured using conventional high-productivity methods while third fire decoration is reserved for complementary articles.