Varnish, Lacquer and Shellac
Varnish, Lacquer and Shellac
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Classic varnish, lacquer, and shellac are often the best possible finish for many jobs. Knowing which to use in various projects, will allow the proper finish to be chosen in each situation.
Before we dig into the details, let’s talk about why we need a different varnish for outdoor applications. Any wood stored outside is going to be exposed to a wide range of temperatures and weather, as well as a good dose of damaging UV rays. These elements serve to break down the finish over time. Furthermore, changes in humidity cause the wood to expand and contract, and a standard indoor finish would simply crack and deteriorate under these conditions.
Over thinning reduces the total solids applied per coat and more coats must be applied to get the same thickness of coating and protection for the surface. Overly thinned lacquer creates many application problems. If flow characteristics need improvement the proper additives should be used to accommodate climatic changes.
For centuries, lacquer finishes have been used to give woodworking a long lasting, durable water-resistant finish. Lacquers are available in two styles: spray and brush-on, although they’re both among the fastest drying finishes. That said, brushing on a lacquer finish is more diligent and precise work and takes longer, but is also cleaner than spraying on finish.
If you do a quick search of the internet for articles on shellac you will find hundreds, maybe even thousands of them discussing different aspects of this historic product. You will undoubtedly find articles discussing shellac's history and origins. Just in case you don't know, shellac is a resin secreted by the Lac Beetle and primarily harvested from India and other countries in south Asia.
I would like to get into spraying more lacquer because its looks great and dries fast, but all the options out there are confusing to someone new to spraying, like me. Post-catalyzed, Pre-catalyzed, nitrocellulose, water-borne. What are the differences and what should I start with?
While I am certainly no expert at furniture finishing, I thought I would like to share with you my favorite method of finishing wood. I find the finish part of woodworking to be the most relaxing and rewarding part of my hobby. I do not like to stain wood if I can help it, nor do I like the look and feel of polyurethane type finishes.
Poly varnish can not be applied over shellac that contains wax. Knowing that most shellac contains wax, poly manufacturers say not to apply over shellac.
Once you have built your woodwork projects and sanded them smooth, you'll need to get them ready for the finish and final decorating. Few supplies are more important than tack cloths. Usually make of cheesecloth and soaked with a mixture of varnish and turpentine, they're very sticky and are used to remove sawdust and fine wood particulate from the projects. Tack cloths will prevent your projects from having that "crinkly" look to the finish. It's an extra step, but the last thing you want to have happen is for one of your projects to look like it was poorly made.