SORTA-Clear™ 18 and RTV-5220 are both soft transparent platinum-cure silicones for flexible molds and detailed casting applications. SORTA-Clear™ 18 is specified at 18 Shore A, while RTV-5220 is listed at 20±2 Shore A. The published hardness specifications are therefore relatively close, with the RTV-5220 range overlapping the nominal hardness of SORTA-Clear™ 18. Mold geometry and demolding requirements should be considered alongside hardness when selecting between the two materials.
For transparent molds, visibility is a practical feature rather than simply an appearance characteristic. Smooth-On specifically positions SORTA-Clear™ 18 for prototype and jewelry molds where model visibility is important, including applications where the mold can be cut to remove the master. Its clear appearance can make it easier to locate the master, inspect internal details and plan a cut line during demolding. RTV-5220 is also positioned as a transparent silicone for clear molds, resin crafts, miniature molds and other flexible applications where transparency is important.
The published mechanical data show higher reported tear strength and elongation for SORTA-Clear™ 18. Smooth-On reports 545% elongation and 80 pli tear strength, while RTV-5220 reports 400±50% elongation and 10.0±0.5 N/mm tear strength. Tensile strength is reported at 425 psi for SORTA-Clear™ 18 and at least 2.5±0.5 MPa for RTV-5220. These figures should be treated as manufacturer-published reference data rather than a direct laboratory ranking because the test methods and conditions may differ.
Processing time presents a more substantial production difference. SORTA-Clear™ 18 has a published 60-minute pot life and 24-hour cure time, while RTV-5220 is listed at 40–50 minutes and 6–8 hours. SORTA-Clear™ 18 therefore has the longer published working window, while RTV-5220 has the shorter published cure cycle. The difference may be relevant when balancing working time during mold preparation against the required mold turnaround time.
Viscosity is another notable difference in the published specifications. Smooth-On reports a mixed viscosity of 21,000 cps for SORTA-Clear™ 18, while MinghuiLink reports 50,000±5,000 mPa·s for Part A of RTV-5220. Because these figures are reported for different material states, they should not be treated as a strict like-for-like viscosity comparison. The published data nevertheless indicate different processing characteristics, so the appropriate mixing, pouring and air-removal procedures should follow the respective manufacturers’ technical documentation.
