Polypropylene Fiber is a reinforcing fiber that is quicker and easier to introduce into a lime mix than traditional animal hair. Simply sprinkle it into the mortar and mix for a few minutes to distribute the fibers. Polypropylene fiber and animal hair gives plaster lateral strength.
Real animal hair is very challenging to disperse into lime mortar. The majority of hair used in historic lime plaster was either horse, pig or goat hair. Using today’s modern mixing methods, long horse hair becomes entwined in mixers, hoes, and beater attachments. This is extremely frustrating!
Real animal hair is also very expensive (unless you own the animals!). Real animal hair needs to be “folded” into a mix to be work-able. This is very time consuming!
For base coat of plaster (NHL 2.0 or Lime Putty Stucco/Plaster Basecoat) you will need approx 3 oz (three tightly packed cups) of Polypropylene Fiber per five gallon bucket of plaster. Actual amount needed will vary depending on installation techniques.