Catalyst is supplied free with most resin packs.
Liquid MEKP. All resins must have catalyst to start the hardening process, added at 1% - 3% by weight.
Ideal addition is 2% (20ml per kg of resin).
The speed of catalyst you need depends on your working temperature:
SLOW: 20ºC +
NOTE: this is a guide, as other factors, such as direct sunlight, can also affect cure speed.