FORTA-FI is added bag and all, at any point in the mixing process after the fines collection and before the addition of the liquid asphalt. While the fibers disperse uniformly and completely in seconds, it's best to allow as much mixing time as possible. Due to the many variations of asphalt mixers available, the specific location must be selected by the producer to work best with their process. Experience has shown however, that FORTA-FI mixes very easily.