In this study, we investigated the color change of the normal light gray granite as the high value color granite. By coating the metal catalyst liquid on the surface of granite stone, the metal particles were penetrated into the granite and the color of granite was changed permanently through the annealing treatment. To increase penetration depth into the granite, we used DC (direct current) bias. Two kinds of bias were used such as DC bias and pulse DC bias. And the penetration time was changed as 30 and 60 min. In all cases, the color granite were successfully obtained. Regardless of the catalyst reaction time, the penetration depth was increased by using the bias treatment. We obtained a penetration depth of 21 mm with the DC pulse bias during 60 min.
