Question: what is the difference between iso and ortho resin?
Answer: Orthophthalic (Ortho) resins are based upon orthophthalic acid and are a good basic, general- purpose, inexpensive resin. ... Iso resins have between 42% and 50% styrene because the higher molecular weight more solvent is required to create a workable viscosity. Iso Resins typically cost more than Ortho resins.