Particularly visible in home improvement stores during spring, film forming coatings are sold as deck, weatherboard and general exterior wood finishes.
Common performance claims include "new formula" or "improved durability".
The film formed by these coatings create a physical barrier to the elements, and protect the wood, for a certain period of time. Film forming coatings do typically hold colour longer than degradable pigmented stains, and penetrating oils.
The issues occur when the film starts to degrade, and flaking and cracking begins to occur on the surface. As many film forming wood coatings contain a yellow/brown UV inhibitor, the contrast with the exposed wood creates a patchy appearance.
In most instances, once the film has begun to break down, the remedial work becomes onerous. It is advised that the remaining wood coating should be removed completely, and that a oxalic acid based cleaner is then applied to the wood, prior to re-coat.
Abodo does not recommend film forming coatings. Our own range of Protector Oil finishes are penetrating with a degradable surface. This means that they penetrate into the wood and will slowly abrade back over time, without leaving surface film on the wood.
When the inevitable maintenance cycle is required, home owners can simply wash their decking or cladding, and then reapply the oil, - without stripping back the existing wood coating.