The stuff you're referring to sounds to me like Smooth-On 2-part mold
compound, a 1:1 ratio product marketed to those of us without a
vacuum machine. My casting mentor, David Brand, intoduced me to it,
although he himself did not think highly of it. I've used it for a
couple of molds (yes, blue stuff + pink stuff=lavender stuff) and
found that it does faithfully reproduce detail, but it pours very
thickly and the resulting casts (wax, in my case) have to have some
bubbles shaved off.
Hope this helps!