Board Thread:Theories and Speculation/@comment-5407586-20150624095943/@comment-25549954-20150701172424

Yes, what Deidara does is uses his earth material clay and adds Exposion chakra (which contains Earth chakra along with presumed lightning chakra), he normally doesn't use his earth sign or may be we weren't shown only to be revealed by Sasuke's Sharingan. When he used his C4 he made Earth hand sign to expand and move it, then he uses Katsu hand sign as shown in ch 360 to explode, the explosion takes place afterwards as shown in Sasuke's genjutsu. I assume that C4 required large amount of chakra control that's why he weaved Earth hand sign to move the clay made partly of earth chakra.