Perhaps you poked too early and your relief holes "closed over", & then the repour was not hot enough to melt thru??? Sometimes it's necessary to poke more than once, depending on the size of the mold. In the past I used 4625, but I now use 1343, which is almost the same as the 4625, except that 4625 is a pre-blend & 1343 is not. Pouring temperature will not affect the transparency.