Most paints and clear finishes are solvent based. The solvents, or thinners, are what enable the finish to be applied with spraying equipment. When they evaporate, the finish hardens and sticks to the surface. 2 pack finishes work differently. A 2 pack finish consists of two containers (packs) of liquids:
- One pack contains a resin composed of acrylic paint and melamine
- The other pack is a hardener, polyisocyanate resin
When the two packs are mixed together, a chemical reaction occurs that causes the mix to harden. Because only a small amount of solvent is in the mix, almost nothing is lost by evaporation and the result is a thicker, harder finish. This makes the surface extemely durable for kitchen cabinetry surfaces. The disadvantages of 2 pac are all in the process of applying the finish:
- 2 pac dries slowly, so must be applied in a dust-free environment.
- Heat speeds up the drying process, so a temperature controlled environment is ideal.
- The hardener contains isocyanate, a toxic chemical. The person who sprays a 2 pac finish must wear a special breathing device and work in a ventilated spray booth to apply it safely.