All wood panels must be sized, or sealed, before painting to contain the natural chemicals within the wood that can break a painting down over time. Support Induced Discoloration (SID) occurs when a panel is not properly prepared and these chemicals leach through to the paint on the surface. By choosing a denser panel with a low acid content, an artist greatly reduces their risk of SID. However, all wood panels should be sized (sealed) and primed before painting to ensure their longevity.
Traditionally, panels were sized (sealed) with hide skin glue before applying the Gesso grounds. However, current research has shown that hide glues like rabbit skin glue do not completely seal the surface, and deteriorate over time. Conservators consider a PVA size or acrylic resin a superior modern substitute for hide skin glue. If you are sealing your own panel such as Ampersand’s Hardbord™, we recommend using GAC100 from Golden®. This is a superior sealer for panels. Its high resin content seals the panel very well and forms a good film on the surface. GAC100 also forms a good foundation for proper adhesion to layers of gesso. With Ampersand’s coated surfaces such as Claybord™ and Gessobord™, Ampersand uses their Archiva-Seal technology to seal their panels prior to applying their painting grounds. This technology employs a specialized method to apply their proprietary sealers so that the actual fibers of the board are sealed. This sealing process creates a barrier between Ampersand’s acid-free coatings and the hardboard surface, ensuring that an artists’ work will be protected over time.
Prior to sealing, make sure your panel is clean of any dust or debris. Some experts recommend that you slightly sand the surface of the panel to ensure good adhesion. Note that Ampersand Hardbord should not be sanded. Removing the top layer of tempered fibers can cause the panel to warp when gesso is applied. Next, apply GAC100 liberally with a brush onto the panel. Take a putty knife or spatula and work the GAC100 into the fibers of the panel while it is still wet. Smooth it out and let this first layer dry. Next, apply two additional coatings with a brush, letting each layer dry in between coatings (no need to sand between layers). Make sure that the sealer is evenly distributed throughout the surface. It is highly recommended that you seal both sides of the panel to retard moisture penetration on the front and back and to equalize both sides of the panel to prevent warping.
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