Problems With Old Wood Finishes

For the best results, lighten the existing finish on older wood.

If you'd like to restore old wood by applying a new finish, recognize potential problems before they occur, or disappointing results may prove likely. Older wood requires extensive preparation before it will accept a new finish. To give yourself the best chance for success, learn the dos and don'ts of refinishing.

Existing Finishes

Older wood is typically already finished with stain, varnish or both. If you apply a new finish over the top of the existing one, one of two things is likely to occur. Because stain and varnish saturate wood, they leave little opportunity for fresh finishes to adequately absorb. This tends to cause pooling and dripping, and the inconsistent absorption may lead to blotchy results. In addition, if the wood is already stained, the new finish will likely make the wood appear too dark.

Stripping

Before you apply a fresh finish to older wood, strip down the existing one. If the old wood is finished with varnish or a solvent-based sealer, you must sand off this layer before application. If the wood is colored with existing stain, lighten the finish by wiping the old wood with paint thinner.

Grains

Most older woods are made of hardwood --- a surface poorly suited for liquid stain. This is an important concept every do-it-yourselfer should understand. Unlike softwoods, such as pine, fir and cedar, hardwoods have dense wood grains that prevent stain from permeating their hard exteriors. If you apply ordinary liquid wood stain to old hardwood surfaces, expect a splotchy finish. To encourage a uniform appearance, coat your old hardwood with a slow-absorbing gel-based stain.

Considerations

If you are trying to finish old exterior wood infested with mold, mildew and insects, you will have little chance at success. In addition, if portions of the wood are affected by rot, a new finish will do little to prolong the life of the surface. Replace these types of surfaces with new wood before applying a fresh finish.