One would tend to think that everyone in the stone sector obviously knows what the tests in natural stone are, what they mean and how to interpret them. But the most common situation is something like this -the architect asks, pompously, for the test results of the stone being evaluated. The seller (he has no idea at all what they are ), replies: "Of course! Here they are!" , and he fishes out a photocopy with a lot of official looking stamps and numbers. The architect (he too probably has no idea at all but cannot afford to look foolish by asking what they mean), has a look, does not understand a thing but is impressed by all those impressive stamps and signatures, says: "O.K., now let us talk of the delivery schedule"

This is more or less the reality never mind the hundreds of conferences, articles, technological centres, laboratory centres that exist in relation to the topic. The objective of this article is one more attempt to clarify some basic points relating to the testing of natural stone. These mentioned tests have been approached from a non- academic point of view assumes that the reader is totally ignorant , and the aim is that after reading the article one has at least a general idea on the topic. However, it is for the reader to judge up to what point this article achieves the objective.

THE NORMS OF THE TESTS IN NATURAL STONE

The first problem that one encounters on examining the laboratory data on a determined natural stone is the norm used. The norm used is no more than the description of the test that has been done. The Spanish norm, for example : the U.N.E. defines all the parameters for the realisation of the test (type of testing sample, the number of testing samples, machines to be used, the temperature and humidity conditions , etc.) that measure the precise properties of the stone. In other words, the ruler for measuring each property is defined.

A test that does not reflect the concrete norm does not indicate anything about the properties of the stone, since we cannot know of a measurement without knowing the ruler used.

Therefore, if we analyse the property of absorption of water of two different stones using the U.N.E. norm 22-182-85, which defines how to do the absorption test, we can find out which of the two absorbs less water.

But the problem begins when we find that in every country there is a different norm (the NF in France, ATSM in United States, the IAPMO in Singapore , etc.) because every country defines the tests in a different way: each country defines its own ruler of measurement of each property in a unilateral way. If we were to have two tests of two stones that use two different norms, different ruler, the comparison of the properties oft he two is impossible. It is not rare to see in a big project where different stones are competing that presented with a large number of different test results of each one of the candidate stones those in charge of the project are not able to compare any of the properties since each stone has been analysed using different norms.

The actual situation of the norms sometimes leads to each of the property of the same stone being tested according to the norms of each country where the stone is to be commercialised with all the extra costs and confusion that this implies. This is perhaps one of the reason why the world of stone offers such a deficit of technical information to the consumer about its own products. This lack of information may have led several times to the choosing of other materials of which more technical documentation is offered. However, there is a new element in Europe which hopefully will modify the mentioned deficit in a radical way in a few years: the policy of standardisation in the European Union.

In a general way in the European Union the development of this policy has the following objectives:
Oblige the companies to have the tests of the different stones being commercialised so as to allow the users the choice of the stones with physical characteristics in accord to its use.

Unification of the European norm with the aim of simplifying the interpretation of the tests in the whole territory of the Union and permitting the possibility of comparison. This is to say, the adoption at a European level of only one ruler.
The importance of these measures should be taken into account because it would imply a much greater importance of technical characteristics as a sales tool.