If you’re trying to decide between liners and polyurethane for your tabletop, you can stop scratching your mind: They’re basically the same product. The choice between varnish and shellac, however, is a real one, and do not forget to add lacquer for your list of alternatives. It is similar to shellac in a few ways, but it is a different end, and it is among the very popular and powerful tabletop finishes you may use.
Treating vs. Non-Curing Finishes
Varnish, whether it contains alkyd or polyurethane resin — or a combination — is an illustration of a healing finish. Once the solvent dissolves, the resin undergoes a chemical reaction that can’t be reversed. Shellac and lacquer, on the other hand, simply harden by evaporation of the solvent, and if you add more solvent, these finishes can become soft again. Curing finishes resist a wider selection of solvents, while evaporative finishes are more delicate and easier to repair. Unlike the solvents in lacquer and shellac, those in varnishes evaporate slowly, therefore varnishes level nicely once you apply them using a brush.
Shellac and Lacquer
When you apply a shellac finish, you’re coat your tabletop with resin secreted by insects. This resin — called lac — is harvested from tree branches and condensed into flakes. When dissolved in denatured alcohol, the flakes make a thick solution which you can spread using a brush or spray. Lacquer originally comes from tree sap, and also the kind that ancient Japanese craftspeople utilized was a healing finish. Modern lacquer, however, is composed of a non-curing cellulose or acrylic resin dissolved in volatile solvents. The solvents evaporate quickly, which means you have to spray lacquer, unless it contains an additive to retard evaporation and leave the product brushable.
The benefits of Evaporative Finishes
People have appreciated shellac over the years because it gives a delicate and durable finish. The end on several antiques is shellac, and it is usually the ideal end to apply to your antique tabletop. Modern lacquers were not developed until the 19th century, and also among the reasons for their popularity is that they’re sprayable and dry fast, which means that you may apply several coats fast to build up the end. Because evaporative finishes soften once you apply solvent or fresh finish, they’re easier to repair than curing finishes. They achieve their best hardness after waxing and buffing.
The Varnish Alternative
One of the main ingredients in varnish is linseed oil, a hardening oil derived from flax seeds. Conventional varnishes include plant alkyds, which harden and cure to form a permanent film. Modern varnishes, on the other hand, frequently contain polyurethane, which is a synthetic plastic, or a combination of alkyd and polyurethane. A varnish finish is not delicate — alkyd varnishes have a tendency to yellow, and polyurethane varieties have a plastic-like look — so that they aren’t ideal coatings for fine furniture. They are resistant to a lot of strong solvents and may soften lacquer and shellac, though, and therefore are ideal for outdoor tabletops, bar tops and utility components.