THI-VEX™ is made especially for thickening Smooth-On silicones for vertical surface application (making brush-on molds). Different viscosities can be attained by varying the amount of THI‑VEX™ added.  THI-VEX™ is added as a percentage of Part A and must be thoroughly mixed with Parts A and B.  THI-VEX™ is skin safe and certified by an independent laboratory.