Fill it! Fillers are dry materials that are compatible with Alumilite Polyurethane Resins. Fillers thicken and expand the volume of the casting plastic. It is best to not fill over 100% by volume, eliminating the chance of compromising physical properties to an extreme. Fillers can make the resin heavier or lighter, change its appearance and reduce shrinkage. We only offer 3 fillers out of many that are available in dry fillers. Micro balloons, tiny glass spheres used to thicken or extend volume. It will make the finished part lighter or float in water. Porcelain Powder is ground porcelain used to thicken or add weight. When it is mixed into White Alumilite Casting Resin, it will achieve a cold cast porcelain look to your cast pieces. Atomized Aluminium Powder, is powdered aluminum that will add weight. It is used to make vacuum molds where high heat is present, increases the heat service temperature from 225F to approximately 450F. Aluminum Powder stops shrinkage in parts where close tolerances are important. It will give an aluminum-look to your cast pieces.