there are about 4 different types of anti icing fluids, all with different hold over periods.
Now, the fluids with the longer hold over period usually have a higher viscosity compared to the shorter hold over periods.
So the rule is you can't use the longer hold over periods on small planes generally because it won't get blown off during takeoff/initial climb, this can make it have a similar effect to icing.
http://aircrafticing.grc.nasa.gov/courses.html
this is the best resource i've found related to icing, I spent about 5 hours just going through the ground de/anti-icing section. Have a read, you will learn heaps from it!