The development of these caulks was on a 50% solids cut of butyl rubber 035 in mineral spirits. This cut can also be purchased in VM & P if faster solvent release is desired. Obviously, the butyl rubber could be bought at 100% solids and cut by the caulk manufacturer at considerable savings; however, many producers might not have the equipment to efficiently produce a good cut. Non-staining grades of butyl rubber may offer some advantages in color after long exposure and this should be evaluated where maximum color retention is considered to be major importance. A heavy duty double sigma blade Baker Perkins mixer is the type of equipment recommended for making these formulations and the suggested technique is as follows. Roughly one-half of the butyl cut is added to the mixer, followed by the ATOMITE, rutile titanium dioxide (for white caulk) and International Fiber, in that order. The Indopol H-1900 and/or a sufficient amount of the remaining butyl cut should be added as necessary to incorporate the pig