Differences in Polyurethane for a Wood Table

Types

• Several different types of polyurethane are available for furniture. The most common is oil-modified polyurethane, which has a petroleum base. This material must be diluted with solvents and takes eight or more hours to dry. Moisture-cured polyurethane is more durable and waterproof than oil-modified finishes but has a strong smell and is much harder to apply. Curing time depends on the humidity level in the room. Water-based polyurethane yellows less than oil-modified types and has a very mild odor. Water-based finishes also dry faster but cost significantly more than other types.

Application

• Polyurethane finishes come in brush-on and wipe-on formulations. Brush-on types are traditional but add the risk of leaving brush marks. Wipe-on polyurethanes require a lint-free rag and must be applied in very thin coats to avoid unevenness. Wipe-on polyurethane dries more quickly and works best for small tables, while brush-on makes a better finish for larger furniture.

Benefits

• This modern varnish offers better abrasion, solvent and heat resistance than most other options. It also provides better moisture resistance, even if the liquid isn't wiped up immediately. Because of its durability, polyurethane varnish doesn't need to be reapplied as often. It works well on new tables that will see a lot of use, such as craft tables or kitchen tables.

Disadvantages

• This finish makes a poor choice for restoring antiques and can actually damage some older tables. Polyurethane is hard to repair once damaged, interacts poorly with older types of finishes and can increase wood shrinkage by blocking moisture from the material. It also off-gasses as it cures.