"The most modern method is described in patent application WO 03/027042 (Luca Toncelli, Apr. 3, 2003) comprising two alternatives depending on whether the binding product forming the board is of the "cement" type or the "polymerizable resin" type, the powdered pigment being used in the first case and pigment in liquid form in the second case which is the one most closely related to the present invention. Once the base mixture formed by a granulated material and an aggregate has been made, it is deposited on a support and the solution containing the pigment is sprayed on the surface with a nozzle in a localized and random manner so that patches or blotches of another colour are produced without producing pigment agglomerations. Then, the mixture is subjected to the compaction phase with vibration under vacuum and subsequently to the hardening, cooling, cutting and polishing phase. Another variant of the method consists of the surface of the mixture being treated, before or after adding the solution with the pigment, with an instrument such as a rake conveying an undulating movement to the surface of the mixture such that the colouring solution is distributed more unequally. The result of this treatment after adding the solution with the pigment is that the patches or blotches of pigment deposited in the surface are distributed acquiring the desired veined effect."

(Cruz, US Patent 7,815,827; 10/19/2010)

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