So I'm back. Its been a while since I posted my last blog On Wax. About three years actually. Since then I have moved to New York via England. I will save you the details for now. Because I would like to pick up where I left off. I would like to talk about finishes.
This is not intended to be the end all guide to finishing. It is for those of you who may need to ask the question... "What type of finish should I use on my furniture?"
I am going to break it down chronologically. Finishes along this timeline also happen to progressively increase in resilience and durability. So we start with fire.
Fire, wax, and oil were some of the first methods people used to protect their wood. More or less sealing the wood from the elements. Prolonging the natural breakdown of it's fibers. The British would scorch the bottoms of wooden posts they would use for framing structures. This would create a water barrier and transform the natural sugars that wood eating bacteria feed on. Therefor warding off rot. The Japanese shou sugi ban treatment was created to protect whole wooden structures in the same way. They would char cypress leaving a beautiful shimmering black exterior protected from bugs, UV light, water, and rot. You will find this process is still being used today all over the world.
Wax was also adopted around the world as a protective wood coating. By using wax directly on wood furniture you create a beautiful satin sheen. Smooth and satisfying like a new bar of soap. It was a very common finish that people took pride in keeping up. Dirt dust and oils would be trapped in the wax creating what we refer to today as a patina. If you have the passion it takes to keep up a straight wax finish. The rewards will be an organic beauty like nothing else. Ask me questions any time or for basic information look back through my previous blog On Wax. First understand this. Once you wax raw wood there is a very good chance you will not be able to finish it in any other way. Most film finishes will peel right off of wood that has been waxed. To remove the wax from the wood you would need to wash it down many times with hot caustic soda water and or toluene. Both are not pleasant, and may dry out the wood to a point beyond salvaging.
Oils like teak and tung oil have also been used for a very long time as a protectant. These finishes also require upkeep. But they hold a very special place in the world of wood finishes. Oils have been developed over the years to provide great resilience in wet environments. Mineral oil or salad bowl oil is safe to put on wooden surfaces you prepare food on or in. If I were putting in wooden kitchen counters I would look at the Waterlox line of oil finishes. Besides this I would have to say oil is one of the least common finishes. Besides some danish and teak furniture I can't say I have used it that often for furniture applications.
All of the previous finishes each provide a unique look. But they are not resilient. For added protection of wood people developed the film finish. The original film finish was shellac. Shellac was used in India more than 3000 years ago for many purposes. It started as a basic resin. Farmers would infest trees with lac insects. These insects would coat the small branches of these trees with this scarlet amber resin. The branches would then be processed to remove the resin. Crushing it heating it and straining it until they had a raw unrefined version of shellac known as seed lac. It wasn't until this seed lac was further refined by heat and or solvent to remove further impurities that it could be called shellac. This could now be melted with denatured alcohol and applied to wood as a liquid. The alcohol would off gas quickly leaving a protective film. Processes were created to apply shellac such as French polishing. This was a way of burnishing the shellac with a soft rolled cloth referred to as a tampon along with boiled linseed oil. This would give furniture a glossy wet look and bring out the figure in the wood or showcase decorative marquetry. It was common to apply wax over a shellac finish as an extra layer of insurance. I feel that it also brings an added textural and visual appeal to the piece. Shellac has been used as the primary film finish for furniture in England since the 1700's. Shellac was easy to damage so people were much more careful with there furnishings. But when it did get damaged it was easily repairable. I would say in this day Shellac or French polished finishes should be reserved for fine antiques. A proper French polished finish is probably the most honorable way you can treat a piece of wood.
From here everything gets mixed up with the introduction of Varnishes. These were created by combining resins, oils, and saps. This was an alchemy all its own. Different recipes were evolved to serve different purposes. One of the most common still in use today is spar varnish you may know it as marine varnish. This was a film finish developed to protect the wood on ships. using the shellac resin and alcohol vehicle they would add pine sap and other organic compounds to keep the finish malleable. In other words it never dried completely. This allowed the finish to move along with the bending mast as the sails caught wind. Shellac alone was too brittle and would crack under this stress. Marine varnish was also very good at repelling water. I would never use this finish on furniture you regularly come in contact with because like I said before it never completely cures. But if you are not coming in contact with it and you want the look of a film finish with good UV protective qualities it is certainly an option. If you are working on an outdoor project though I would recommend you take a look at Cabot's line of sealers. These sealers also have great UV protective qualities. Where the spar varnish has a life of 2 to 5 years before needing another treatment. The Cabot's have a 5 to 15 year life depending on the opacity and environment. It just doesn't have that film finish look.
From this creative alchemy of mixing organic compounds to make varnish. The automotive industry developed nitrocellulose lacquer in the 1920's for our automobiles. Polymers and nitrocellulose fibers replaced the shellac resin and lacquer thinner(a mixture of butyl acetate and xylene or toluene) replaced the alcohol. This mixture could be sprayed on because the lacquer thinner would evaporate very quickly leaving nothing but the polymer resin to harden. This was the beginning of modern man made film finishes. In the 1940's the furniture industries started using nitrocellulose lacquer. When I started finishing furniture this is all we had. It was a very forgiving finish. You could apply it with ease. it was a high gloss finish that you could dull down with flattening paste(basically cotton fiber). If you were to add old yellow and brown aniline dye to a satin sheen lacquer you could achieve that same amber glow of a shellac finish though much more durable. I would use this finish again if I were to restore a classic piece from that era. But for reparable nitrocellulose lacquer finishes things have come a long way.
Pre-catalyzed lacquer aka Precat became the industry standard soon after I started finishing furniture. This is still the most commonly used finish today. In the beginning there were a lot of problems with inconsistency as the different producers bought each other out and changed their formulas. But several of the larger companies like Mohawk refined their products to be a very reliable finish. When it comes to putting a film finish on a modern day serviceable piece of furniture. This is the one I would choose. You can still mix with aniline dye to achieve that classic amber look. You can also get it in a non-yellowing "water white" which is super clear if you are not trying to draw attention to the finish. This finish is far more water and scratch resistant than their predecessors. Probably the most important attribute to this finish is that it is easily repairable. This is the most important point you can take from this post. When it comes to choosing a finish. You want something durable. You want something you don't have to worry about getting damaged. But there is no such thing as an impervious finish. The finish you choose will get damaged. When it does, you will want it to be repairable.
This is where we cross the line into non-repairable finishes. Starting with post-catalyzed lacquer and conversion varnish. These finishes are very resilient to water, heat, and chemical interaction. They are activated just before application with an acid catalyst. They dry very hard and they can not be chemically removed. In other words you can not strip and refinish a piece without mechanically sanding off the finish. This is very laborious, and in most cases not worth the trouble. These finishes are also not very flexible. If the substrate they are applied to were to flex. The finish would crack or shatter. Also a blunt trauma from something like silverware or a paper weight will easily chip it. Since you can't reamalgamate the finish any repair will be very noticeable. Despite all of the possible pitfalls. You will find this finish applied on kitchen cabinets, restaurants, and hospital surfaces.
Another finish commonly used in the restaurant and hospitality industry is polyurethane. This is the modern day varnish. Polyurethane and more flexible Acrylic polyurethane are as resilient as you can get. When people think of polyurethane its the yellowing plastic finish found on factory made furniture of the 60's and 70's. New polyurethanes have been formulated to provide the same look and feel of the lacquers we have grown to prefer. I have used Ilva TP11 polyurethane and precat on the same piece of furniture and you would not be able to tell the difference. I grew up hating polyurethane. Only using it on teak, and other applications where normal lacquer would not work. Having tested these new coatings I would definitely say they have their uses. For a top surface of a table or buffet. Anything that gets a lot of regular use. The only finishes more durable than these will not give you that same classic film finish look. Poly finishes are expensive, very hard if not impossible to repair, but they are chemically strippable.
I will round things out with a few ultra hard finishes. Two part finishes or epoxy finish has been commonly used on bar tops. It is a permanent finish. It is poured on and dries very thick and clear. Epoxy will crack, chip, and shatter due to its lack of flexibility. It too is not strippable or repairable.
Finally I would like to highlight a new type of furniture finish just breaking into the market. powder coating. This process used to be used for metal. In the way that a metal substrate was electrically charged allowing the polymer particle powder to adhere to the surface. The piece would then be baked in an oven. Melting the the powder into an ultra durable coating. This coating is not effected by water, heat, or chemicals. I have even seen it hit with a framing hammer hard enough to drive a nail. There was little or no damage. The BTD wood powdercoating company is developing this finish, and making it better every day. It comes in clear and a myriad of colors and sheens from flat to high gloss. Sounds great and it is. But as of now the finish can only be achieved on a special type of MDF. This MDF has a moisture content that allows the material to be electrically charged the same as metal. They have all of the tools and CNC machines to fabricate almost any shape you can think of up to 1-1/2" thick. Think about it. Get creative and give these guys some business.
So that's about it for now. Until the next big thing comes along. I'm sure with developments in nanotechnology we are not far off from another coating breakthrough. I know this was a very broad explanation of this subject. But I hope it helps with understanding the choices you have. If you liked this post please share it or leave a comment. I am happy to answer any questions you may have or elaborate further on any particular finish. Thanks for stopping by the site. Come back soon for more project pictures and posts.