Prep key to refinishing wooden doors

Q: I have a beautiful old, stained wooden front door that is in good condition. I have tried to refinish it twice, but the glossy finish does not hold up. How should I finish it next time so it lasts? -- Jen P.

A: The workmanship on many of the heavy older wooden front doors is truly beautiful. It is very important to have a good finish on the door. The finish obviously makes it look good, but it also protects the wood from the harsh outdoor weather. Just a little moisture getting under the finish can do irreparable long-term damage to the wood.

No matter what type of final surface finish product you choose, proper surface preparation is important for a long-lasting, durable finish. The door surface must be thoroughly cleaned and free from dust, wax and old loose finish. Some coatings, such as urethane, will initially stick on a dirty surface and look good, but will flake and peel in a year or so.

Since you have a stained door, it might be wise to chemically strip off the old finish and start restaining it from scratch. This will ensure the stain density is uniform and most likely highlight the beautiful graining to a greater extent.

Use a gentle chemical stripper. Be careful when you scrape so you do not damage the crisp edge detail.

When you visit your home center store to purchase the finish, you will see many products from which to choose. The majority of them can be put into three categories: urethanes, varnishes and shellacs. Some of them will include a stain, but stay with the clear ones for the best appearance.

Urethanes and varnishes harden by a curing process instead of just drying as shellac does. This makes them a better choice for a front door. Urethane is probably the best choice overall and will produce the longest lasting glossy finish on your door. If you see the word cross-linking on the label, the finishing product cures instead of just drying.

Make sure you select standard or door urethane instead of urethane for floors. Floor urethane might sound like it would be more durable, but it is not best for doors. Front doors expand and contract with changes in the weather and temperature and floor urethane is not formulated to handle the movement as well as door urethane.

Water-based urethane is the easiest to use and clean up, but it may not be best for a stained door. If you want an extremely glossy, glasslike finish, as most people do, water-based urethane may raise the grain. This ever-so-slight roughness of the surface texture may detract from the glossy appearance. Select a nonwater-based urethane. Both types of urethane are durable when cured.

Before you apply the urethane coating to your door, make sure to read the manufacturer's application instructions. Pay particular attention to the recommended time period between applying additional coats. If you wait too long between coats, they will not adhere as well. Also, never shake urethane because it produces bubbles. Just stir it gently, but thoroughly.

If you have trouble finding urethane suitable for use on exterior doors, check with the following companies: Basic Coating 800-247-5471, Martin-Senour 800-677-5270, Minwax 800-523-9299, and Sherwin Williams 800-474-3794. The relative price of urethane is often a reliable guide to quality of the product.