Thickness in ornamental stones

 Mario Zaniboni

The requirements regarding the thickness of ornamental stones are different, depending on the uses. The technological processes are able to satisfy the need to make available slabs of very limited thicknesses, even down to 8 mm. Clearly, the reasons may be different for choosing one or the other.
In the first place, it may not be necessary to increase the walls with slabs of considerable thickness: in fact, on the one hand it tends to reduce the volume of the compartments (even if it is of a contained negativity) and on the other you needlessly weigh down the load bearing walls (and this affects the dimensioning of foundations).
The reduced thickness is substantial when you want enhance translucency, which is one of the prominent characteristics of certain varieties of ornamental stones such as onyx, some types of colored stones, some crystalline marbles. Therefore, the thin thickness meets a growing demand in wall claddings as a result of new trends in interior design; the applications go from cladding in the rooms, to the interior of the elevators, in cruise ships, etc., always aiming towards the double objective of a luxurious and light decoration. Regarding flooring, an element subject to erosion and abrasion due to intense traffic, one should not limit the thickness of the plates, maintaining the traditional 18 mm.
The raw material to be cut into thin slabs can only be that of first quality, so the choice must be made carefully: the stone must be a compact mass and with no visible structural defects.
If one wants to further reduce the thickness of the slabs (less than the 8 mm mentioned above) one can apply an impregnation of resin. It is a rule that is applied especially in the combination of particularly fragile stones such as, for example, the brescia stone, where the separation surfaces (or of contact) among the various constituent elements are not always strongly welded to each other. However, technology has made it possible to produce slabs even till 4 mm thick. The reinforcement can be increased by the application of protective nets on the back side, that is not in view, of the slab. With the choice of protective nets it is possible to cut very thin slabs and the results are more than satisfactory, because the surface dimensions obtainable are increased and, moreover, it is possible to use them in stones of high chromatic value where sawing tends to be quite difficult. Of course, the processing needs to be done very delicately given the fragility of the slabs. This novelty has only gained partial popularity, in spite of optimum results, perhaps due to the difference of costs of this cutting as against cutting in traditional thickness. However, the product is a breakthrough for technology, considering both the decline in unit weight and the increase in production along with a lower consumption of raw material. But one cannot ignore the increase in residues that, logically, affect the economical balance. Thus we can affirm that the thin slabs have great diffusion where there is high added value. That is, whenever the price has a considerable value, but is not decisive.
There are many applications in construction in which the polished thin slabs have found their niche acceptance.
One should be clear that that not everything that is mined in the quarries can be sawn in reduced thickness. Many laboratory tests discourage sawing of less than 10 mm thickness, both in traditional gang saws as well as multi-wire machines due to the high wastage of raw material. The best results are obtained starting from slabs of good size, already polished on both sides and vertical cut, using disk machines in successive phases.
At any rate, the installation of thin or super thin slabs must be done with extreme caution using common sense. They can be installed in the interior of the buildings for classic applications, as dictated by established tradition. They can also be installed in exteriors (stairs or urban design) taking into account the resistance and durability; the aesthetic aspect should not be considered more than the physical characteristics, these have to be respected. Perhaps the decision to use thin slabs over other solutions prevails, but the above mentioned parameters must prevail.
In summary, the thin thickness is an important milestone achieved by modern technology, but, at least for now, it is a niche market that can gradually be increased. However, what has been demonstrated is that ornamental stones typically possess a versatility of use that every day continues to widen, including uses that other alternative products cannot always achieve. In some markets great success has been achieved by previously polished thin slabs ready for installation; the “Do it Yourself” people love it.
It is appropriate to recognize that the production of thin slabs, as well as that of certain special artifacts, bears the signature of Italian technology, which is spreading in the field of processing of ornamental stones in the world. It is an achievement of the twenty-first century united with the traditional ones; innovation and tradition should work together, without competing, and adopting the best of the other.