After the failure of copy prevention methods, watermarking stays the main technical safeguard of electronic copyright. There are many properties that a watermarking scheme should offer such as imperceptibility and robustness. The robustness property measures the resistance of the watermark against some attacks, which attempt to remove it partially or completely. Nowadays, many watermarking schemes exist each of them robust against a certain list of attacks but vulnerable to many others. It is not always easy to obtain new schemes that resist more and more attacks. This paper proposes general mixture techniques to combine the properties of several watermarking methods so as to obtain watermarked objects robust against most of the attacks survived by the combined methods.