Finish Supervisor Damien Leighty has 19 years of experience with WallGoldfinger. In that time he has perfected the craft. In this edition of the Experts Corner, he gives us the ins and outs of beautiful, popular, but labor-intensive polyester undercoats.
"Polyester is a resin undercoat put on tables and other furniture to achieve a full filled, closed pore finish and often associated with a high gloss look, although that really depends on the top coat you apply and how much polishing you do. Polyester is considered elegant and of the highest quality and is often chosen by clients for its impervious surface and flexibility. Its flexibility is advantageous for active woods like crotch mahogany and burl, which are prone to movement with changing humidity conditions. When we say impervious we're talking moisture and chemical resistance.
Polyester also offers a much thicker coating than standard finishes and yet offers exceptional clarity, allowing the wood grain to shine through.
Choosing polyester comes with its challenges and limitations, however. Not all furniture makers offer polyester because of the complexity of handling and applying the product. Polyester is really a three-component system of basic resin, a cobalt accelerator and a peroxide based catalyst. Without getting too detailed, there's an order to safely mixing these highly flammable components. Once mixed, the material must be used very quickly or it will harden (cure) within spray guns and all tools involved.
Applying polyester also takes extra steps, extra curing time and comes at an extra cost, which all must be factored into project budgets and completion dates. Polyester finish is sprayed on with our low emission spray guns. After about a week of curing, it is sanded by machine and by hand. Any colorant required is then applied and then a top coat is applied. If a higher sheen finish is desired, the top coat must again cure a week before being wet sanded and polished.
Polyester also provides some limitations on the types of colorants used and, because it completely covers wood's natural pores and texture into a smooth finish, can show scratches more easily.
So where does that leave you in deciding on polyester or not for your next project? In what I call the 'artistic chemistry' of finish, polyester is a more challenging component and labor intensive process. But if a full-filled, smooth, impervious surface is what you seek, polyester provides incomparable quality and clarity."
