Mold Star™ 15 SLOW and RTV-4115 are both Shore A15 platinum-cure silicones, making them relevant choices for molds where flexibility and easier demolding are important. At this hardness level, the material can accommodate more intricate shapes and undercuts than harder mold silicones, although the final demolding behavior also depends on the mold design and casting geometry.
For users comparing these two materials, processing time is one of the more noticeable differences. Smooth-On lists a 50-minute pot life for Mold Star™ 15 SLOW, while MinghuiLink lists a 35-minute working time for RTV-4115. The longer published working time of Mold Star™ 15 SLOW may be useful when making larger or more detailed molds where additional time is needed for pouring and air release.
The published cure times also differ slightly. Mold Star™ 15 SLOW is listed at approximately 4 hours, compared with approximately 5 hours for RTV-4115 under the manufacturers' stated conditions. This difference may be relevant when mold turnaround time is an important part of the production process.
Viscosity is another published difference, but it requires careful interpretation. Smooth-On reports a mixed viscosity of 12,500 cps for Mold Star™ 15 SLOW, while MinghuiLink reports approximately 4,000 mPa·s for Part A of RTV-4115. Because these values refer to different measurement points, they should be treated as indicative rather than as a direct like-for-like viscosity comparison.
For applications such as resin, gypsum, concrete or other casting molds, the choice between the two should therefore consider the required flexibility, mold geometry, working time, turnaround requirements, casting material and demolding conditions rather than Shore A hardness alone.
