Wood Finishing
Unfinished wood can dry, crack, deteriorate and swell if exposed to moisture.
Wood finishing refers to the process of refining or protecting a wooden surface and is usually done by applying a special liquid to the wood surfaces which then dries into a protective layer.
A good finish prevents swelling and cracking, protects against stains and enhances the appearance of wood.
Types of finish
There are three types of finishes
- Evaporative
Evaporative finish is dissolved in turpentine or petroleum distillates to form a soft paste. After these distillates evaporate, a wax residue is left over. Example: wax
- Reactive
Reactive finishes use solvents like white spirits and naphtha as a base. They will polymerise and the resulting material is less readily dissolved in solvents . Example: Varnishes, linseed oil and tung oil
- Coalescing
Water based finishes generally fall into the coalescing category.
Let’s have a look at the most common wood finnish
Fossil-based Wood Finnish
- Polyurethane wood finishes
Polyurethane isn’t really a type of finish but rather an ingredient. Oil-based and water-based polyurethane are used as protective finish. Polyurethane based lacquers and varnishes have become the most popular type of finish overshadowing shellac and wax.
Oil-Based Polyurethane
Also referred to as solvent-based. Oil-based has higher VOC (Volatile Organic Compounds) content than water-based poly. Solvent-based lacquers involve health and environmental risks. Repeated and prolonged exposure to solvents may lead to permanent brain and nervous system damage. Oil-based poly turns yellow after some time and has a stronger odour than water-based polyurethane.
Water-based Polyurethane
Water-based lacquers are less toxic, more environmentally friendly and less hazardous as they have no combustibility issues. Water-based polyurethane dries faster, is more expensive but less durable. Water-based polyurethane finishing needs more frequent re-coating than oil-based poly.
- Epoxy resin
Epoxy resins, also known as polyepoxides, are a class of reactive prepolymers and polymers which contain epoxide groups. Epoxy resin is suitable for sealing wood as well as waterproofing it.
Bio-based Wood Finnish
Bio-based refers to the non-fossil origin of carbon. We shall differentiate two types of non-fossil carbon: animal and plant based.
Animal-based Solutions
- Shellac
A resin secreted by the female lac bug on trees in the forests of India and Thailand. It is processed and dissolved in alcohol to make it liquid.
- Wood wax
Wood wax is normally a specially formulated blend of carnuba wax, paraffin and beeswax mixed with colors and other wood enhancers.
Problem: You can’t harvest honey without harvesting beeswax. Beeswax is produced by the bees to build comb which is used to house their young and store honey. This practice weakens the bees’ immune system and makes them more susceptible to illness and death
Plant-based Solutions
- Boiled linseed oil
Linseed oil also known as flaxseed oil or flax oil (in its edible form), is a colourless to yellowish oil obtained from the dried, ripened seeds of the flax plant. A linseed oil finish is easily scratched, and easily repaired.
- Nitrocellulose Lacquer
Nitrocellulose Lacquer are nitrated cellulose used as wood coating. Cellulose is the main component in plant tissues. Alexander Parkes invented the first man-made plastic in 1855; it was nitrocellulose: cellulose treated with nitric acid and a solvent. It was branded and patented Parkesine in 1862.
Problem : the cellulose is bio-based but the nitric acid is not what we would call “eco-friendly”.
- Bio-epoxy
This is epoxy made with renewable content, such as soybean oil.
Criteria of Comparison
There are several criteria to compare wood finnish:
- appearance
- protection
- safety
- easy-to-use
- reversibility
- durability (frequency of re-coating of re-application)
- sustainability
Durability and Sustainability
Many wood finnishes have to be re-coated every so many months or years. Durability and sustainability are related to each other. Sustainable refers to “to sustain” (meaning ‘to last’), french durable comes from ‘durer‘ (to last).
The million dollar questions are: is there a method that lasts 100 years? Is bio-based automatically the most sustainable method? Is there an ancestral method more sustainable than bio-based products?
Well there is!
Yakisugi
The most sustainable solution is a traditional method called Yakisugi. It’s craftsmanship. It’s the cheapest solution and will last between 80 and 100 years.
Yakisugi is a traditional Japanese method of wood preservation consisting of burning the wood….. charred timber. Yaki means to heat with fire, and sugi is cypress.
By slightly charring the surface of the wood without combusting the whole piece, the wood becomes water-proof through the carbonisation and is thus more durable. It also protects against insects, as well as making it fire retardant.
Craftsmanship
There’s a pattern that can be found here. A kind of cycle or pathway …
- Animal – It started with animal based-solutions probably during antiquity.
- Fossil-based – The industrial and fossil revolution enabled the production of cheaper solutions that were produceable at industrial scale: it was a chemical / synthetic / fossil-based alternative to the animal-based solution.
- Bio-based – Due to environmental and sustainability concerns, we’re switching to bio-based (non-fossil carbon) alternatives with a reduced carbon footprint.
- Craftsmanship – Do you think we could go one step further to traditional craftsmanship method that may be more “sustainable” for the environment and also more “responsible” towards the community? What if we decided to switch “financial profits” for “employing as many people in our local community” as a real sustainable development goal?
Refs
- Wood finishing
- Lacquer
- All About Wood Finishes
- How Does Wood Wax Work?
- To Bee or Not to Bee: the Truth Beehind Honey and Beeswax
- Epoxy
- Yakisugi
- Linseed oil
- The Difference Between Water And Oil Based Polyurethane
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