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 the 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.