In most instances, we find that users are mixing Performance 65 & 80 by weight rather than by volume. The proper mix ratio is 1:1 by VOLUME. Mixing by weight can cause soft and sticky castings. Pre-heating your mold (120-130F) is always a good practice to help facilitate the cure of the resin. Additionally, post-curing the part in the mold for an hour at 130F can assist with a full cure, especially for small or thin parts. If you have stickiness on the open surface, this could be a result of scraping unmixed resin out of the mixing cup at the end of the pour.