Two of the most popular transparent/natural wood finishes are melamine and PU(Polyurethane). Melamine and PU are both synthetic hydrocarbon polymers which form a film over the wood surface that is coated, thus laminating it. The purpose of lamination is to preserve the wood by not allowing the moisture of the wood to escape, preventing it from damage from the elements and protecting it from wear and tear from use. Both finishes enhance the aesthetics of the wood by allowing light to refract inside the transparent layer formed by them. Both the finishes have a similar application procedure by spray. So, what is the difference between the two?
The main difference is in the life of the coatings and its resistance to the elements.
Melamine was a great improvement over wood polish as a transparent wood finish when it was introduced in the Indian market in the late 80s and the 90s and is popular to date due to its economy. But melamine has its limitations. The film formed by melamine is only moderately resistant to water. It deteriorates when exposed to sunlight. The film easily yellows and looses lustre. The film begins to crack at the wood joints over time.
With the advent of polyurethane (PU) in the late 90s, most of the shortcomings of melamine were covered. PU forms a tougher film than melamine. It is more scratch resistant. It is flexible and does not crack with the movement of the wood joints. It is UV resistant and can be used on woods that are used in exteriors, such as entrance doors and windows. It does not yellow easily and gives a high lustre. The lustre is also retained longer due to its UV resistance.
PU gives clear advantages over melamine as the application procedure remains the same for both and there is no new skill required to apply PU. Thus the work involved takes the same time and effort on part of the applicator.
Consider wood finishing as a one time investment as reworking of wood finishes takes up lot of resources, skill, time and money. Go for the best coating for your expensive teak or other exotic woods as it will not only preserve the wood but also enhance its aesthetics.
Some things to note when applying Melamine or PU
Melamine or melamatt polish as it is popularly known among the painting contractors is usually sprayed over French/hand polished surfaces, which is not the intended procedure of application.
A study of melamine shows that for all intents and purposes, as in PU, was not originally developed as a wood coating. It is a product of innovation and adaptation that these products are used as wood coatings. The adaptation requires a specific application procedure for the product to perform as a wood coating. These application procedures are grossly ignored by applicators and contractors.
|A damaged French Polished door|
Applicators apply generous coats of French polish and NC Based Sanding sealers as a preparation for the final coating by melamine or PU. They do this as their skill set for colour matching of wood is based on French polish techniques.
The melamine and PU films often fail as the solvents in the French polish and NC sealers are not compatible with solvents used in PU and melamine coatings. Also, the solvents in the French polish applied under transparent coatings are exposed to light and begin to evaporate and cause blisters in the polymer film formed over it.
It is thus highly recommended that application of French polish be avoided when any such coatings are applied. Wood coated by French polish has its own charm and should not be over coated by polymer coatings.