Finishing – Window Shutters for Tropical Weather


T
he blistering Indian summers and long Monsoons can have a devastating effect on most wood finishes. The principal challenge for Indian carpenters has been to build and finish doors and window shutters capable of resisting the tropical elements. British colonials in India, who built large bungalows and imposing Palladian buildings with huge windows, would invariably paint their windows and shutters white. This was the best protection against the sun and the rain. However, even this kind of covering did not last indefinitely and had to be repaired every few years. The old paint had to be painfully stripped away and the surfaces prepared once again and then the new primer and paint applied. It was a painful, recurring and usually expensive process. The less affluent in India did not bother overmuch with worn paint and weather beaten shutters and doors.

Colonial Building

Today, things are very different with a large affluent middle class demanding elegant and well maintained houses. The more affluent Indians seem to prefer polished wood surfaces to painted ones, at least when it comes to doors and windows. The polish of choice, and one with which Indian workmen are most familiar with, is shellac applied by hand. Traditional French polish is an art that has been practiced in India for over a century and many workmen excel in it.  Well applied French polish not only looks classy but can last for years. Unfortunately, its great weak point, often overlooked by house owners, is its inability to resist water and harsh sunlight. Shellac finishes rapidly deteriorate in such conditions even if surfaced with lacquer.

Half Finished window shutter

I have come across handsome houses built at great cost with fabulous CP Teak shutters and doors but with their finish utterly devastated by the cycle of monsoons and hot summers. Doors and shutters finished with shellac will suffer as moisture gradually but surely penetrates the finish and begins affecting the wood underneath. It is therefore a mistake to finish door and window exteriors with shellac. A much better alternative is a Polyurethane (PU) finish. A number of reputed Indian paint manufacturers like MRF and Asian Paints supply good quality two-part PU finishes.

I would add a word of caution though to those using Indian teak and other oily woods for their doors and shutters. These woods exude oil for many years after they have been logged and dried. This oil at times can interfere with a finish and ravage it in a couple of years. A few simple precautions, however, will obviate such an eventuality.

For applying a PU finish follow these steps:

First, condition the wood with any conditioner available. I use Varathane wood conditioner for my projects but any conditioner will do, even homemade ones. This brings out the grain and good CP Teak is such a magnificent wood with its complex grain patterns that it would be a shame to stain it.

Then, apply a coat of shellac (one pound cut will do). This will seal the wood and prevent any oil from coming to the surface.

Now, apply a couple of coats of PU sealer if you want a high polish or simply go straight to the PU coating for a more natural finish. I prefer to apply sanding sealer because it fills the pores and renders a flat surface that makes cleaning and maintenance easier.

After the two coats of sealer have dried properly, usually in a couple of days, apply a thin layer of top coat. This can be done with a spray or brushed on. I just use a brush and sand carefully with 400 grit sandpaper between coats. Three coats of PU top coat will give a beautiful gleaming finish that is capable of resisting the worst of weather. Thin coats of PU if applied along with proper sanding will not crack or deteriorate for many years. 

For a less glossy finish, the surface can be rubbed with fine steel wool or polishing compound. This will reduce the sheen or plastic look. 

Some people recommend blending an amount of boiled Linseed Oil with the PU top coat for a more durable, less brittle finish. I have not tried this so far because I have found that a regular PU coat can protect the most exposed doors and windows for many, many years.

24 April 2011

Comments

  1. Great article as always Indranil. Could you please elaborate on the 'homemade' wood conditioners you refer to in your writeup above.

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  2. Pradeep: I used to use Varathane conditioner earlier but found that even better results could be obtained by applying a thin wash of Shellac prior to staining. This seems to work on most wood - Teak, Sheesham, Rubber wood, Oak, Ash, Pine and even plywood. The Shellac has to be diluted well or else the stain will be light. There is also a formula of bioled linseed oil and mineral spirit but I have never tried that.

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  3. This article is very informative and cool. Thanks for share this beautiful article.

    Colonial Shutters

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  4. Hi, can u please tell where i can buy varathane products in delhi.??

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  5. Sweet post. it's about sweating the details!I absolutely loved reading this post.

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