Things You'll Need
90 grit sanding disks
220 grit sanding disks
High-gloss polyurethane, paint or stain
Natural bristle paint brush
320 grit sheet of sandpaper
A high-gloss finish can be applied to plywood if it is prepared properly. Plywood consists of thin sheets of wood veneer pressed and glued together. Quality grades are given to plywood based on the roughness of the surface and the number of blemishes the sheet contains. Plywood, no matter the grade, must be repeatedly sanded with varying grits of sandpaper before a applying a high-gloss finish. The higher grade of plywood you choose, however, the easier it will be to prepare.
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Sand the face of the plywood using an orbital sander and a sanding disk. Use a 90 grit sanding disk if the plywood has a quality grade rating less than "A." Use a 220 grit sanding disk if the plywood has a quality grade rating of "A" or higher. Sanding the plywood will smooth rough spots on the surface.
Remove the sanding dust using a shop vacuum and a damp rag. Allow the plywood to dry. In the event a 90 grit sanding disk was needed for the initial sanding of the plywood, repeat the sanding process using a 220 grit sanding disk.
Apply high-gloss polyurethane, paint or stain to the face of the plywood using a natural-bristle paint brush. Polyurethane, available for indoor or outdoor applications, is a clear protectant that will seal the plywood. Allow the polyurethane, paint or stain to dry following the manufacturer's directions.
Sand the plywood lightly using an orbital sander and a 220 grit sanding disk. Wipe the plywood clean using a clean rag. Apply a second coat of high gloss polyurethane, paint or stain. Most polyurethane, paint or stain manufacturers require two coats to seal plywood properly. Allow the polyurethane, paint or stain to dry.
Sand the plywood lightly using a sheet of 320 grit sandpaper and your hand. Lightly sanding using high grit sandpaper will provide a finish that shines and is smooth to the touch. Wipe the plywood clean using a clean rag.
Polycrylic can be used as an alternative to polyurethane if the plywood will be placed indoors. Poycrylic is water-based and dries faster than urethane. Clean the natural bristle paint brush using mineral spirits to keep it in working order.