Principles to minimise potential problems with Class2 and Class 3 off form Surface FinishesPrinciple One: Most issues with off form surface finishes are associated with moisture.Wherever possible protect the formwork from weather. This includestarping where practical.Principle Two: The phenolic surface film used on formwork plywood is not impermeableto moisture. To ensure that moisture penetration is minimised, releaseagent and form oils …

Grain Raising or Surface SwellingGrain raising is caused by moisture penetrating the phenolic surface film and causingswelling of the surface veneer.The causes of grain raising are: Severe weather exposureFailure to use release agent or form oilDamage to the phenolic surface film i.e. misuse of vibrators, handling damageetc.Faulty phenolic surface filmAs mentioned previously, the purpose of the phenolic surface film is …

Staining in FormplyThe most common stains associated with formply are: Rust stainingTannin stainingPinking – free phenol from the phenolic surface film.In the writer’s experience, most staining is due to rust deposits on the deck at the time ofpouring or iron in the aggregate. These stains appear red/brown and are often mistakenfor tannin staining.Tannin staining is the result of extractives from …