Stone companies starting to resin treat their marble slabs on a large scale will almost invariably receive lots of advices and instructions from agents and area managers seeking to sell them machinery, tools and consumables. Yet, most these consultants have never had anything close to a practical first-hand experience of restoration and enhancement of stone, having just learnt some basic rudiments through watching real professionals at work.
That being so, it often happens that people who are unfamiliar with resin treatment of marble try to teach novices. The students of such “self-promoted instructors” may then believe to have reached fairly high levels of dexterity, and hence decide to hire apprentices and personally train them. This state of things establishes a vicious circle, as it interferes with the process by which knowledge and skills are transmitted from teachers to students, so that within a few generations of practitioners the resin treatment’s repertoire of techniques and methods inexorably narrows. If we look at what the resin treatment is in actual fact – a wide and complex system – we can easily deduce that anyone – anyone, however intelligent and keen – who is taught an incomplete version of the methodology, will never obtain satisfactory results in terms of repair and reinforcement of faulty marble. In this regard, it is worth mentioning a part of the resin treatment system which is far too often underestimated or, worse, completely ignored: the proper preparation of marble slabs before they are loaded on the Resin Line.
Stone processors needing to treat marble damaged with fractures and holes which are so deep to pass through the entire thickness of the slabs, should always block the cavities up before the material is loaded on the plant, to ensure they are thoroughly filled with the resin that is applied to attach the fibreglass mesh. The resin would otherwise seep through the cracks without filling them indeed, and as a consequence the desired strengthening would never take place.
In summary, dedicated stone processors should close the major faults of the slabs on the side of surface – the one which will be then resin coated and polished – to make sure that the voids are saturated with resin at the time of mesh backing. Factory workers can seal holes and fractures with either quick setting mastic or adhesive tape, or even both these products, depending on the amount, extent and depth of cracking and holing. Regardless of which product workers choose, the operation has to be carried out with the slabs held vertically by a robot loader or a clamp connected to the hoist of a jib crane.
A good quality semi solid mastic – suitable to be applied to wet surfaces with trowel or spatula, compatible with the epoxy resin likely to be used for coating the slabs, and coloured to match the hue of the material – is an excellent means to close large holes. Nonetheless, there are cases where the presence of mastic on the mirror polished slabs looks far too showy or even unsightly, for example, if the material has uniform pale colour and background, like cream, beige and white marble varieties. The best way to overcome this drawback is to partially grind the mastic fillings and replace them with mixtures of liquid epoxy resin, oxide pigments and crushed marble.
A waterproof adhesive tape that withstands high temperatures is ideal to seal long hairline cracks, including those which run diagonally. To remove the adhesive strips before resin coating the slabs is not difficult at all; notwithstanding, this job requires attention to detail and accuracy to ensure no residue of tape is left on the marble surface.