Provided herein are methods of formulating a sealant to span an opening and form a seal with surfaces across the opening including selecting a fluid material capable of contacting and adhering to the surface of the opening and which reacts to form a solid material as a result of a thermal reaction, and selecting and intermixing one or more solids with the fluid material to form a composite, wherein the solids migrate within a column of the composite sealant before the composite sealant cures from a fluid to a solid and bonds to the surfaces of the opening, and the change in volume of the lower portion of the lower portion composite sealant into which the solids have migrated, as the temperature thereof changes during curing, is insufficient to cause it to pull away from the surfaces of the opening or fail internally.