The surface should be clean and dry before finishing, but the best choice of cleaning agent may differ depending on wood species, surface condition, and the finish that will be applied. For example, an oxygen bleach like CPR is a great cleaner for log prep, however it can shift the color of woods high in tannin or flavonoid; e.g., oak might turn dark, Douglas fir might turn pink. Always check the data tech for your finish for the recommended cleaner, and always try a small test area on the actual surface before advancing.
If you plan on using a preservative, such as Tim-bor or Boracol, apply it and allow to dry before applying the finish. Borate preservatives are a relatively affordable step of insurance to deter future fungal decay and insect infestation.
When choosing a finish, more pigment will provide greater UV protection and greater longevity- however too much pigment will mask the wood. Paint and solid stains on logs are not recommended-- firstly because they can hide and prevent remedy of underlying issues such as decay; and secondly, because we think that wood is too beautiful to hide!
Read the application data for the product being used and apply the recommended number of coats to increase UV protection. In most cases the first coat going into the wood should be the heaviest saturation. If spraying the finish, back-brush vigorously for proper adhesion and to force it into any small cracks.
Apply the finish at temperatures in the range of 50°F to 90°F. Surface temperatures below or above this range can hinder absorption and shorten the life of the finish. Wind and direct sunlight can also dry a finish too quickly.
In addition to proper preparation and application, another important consideration to get the most life out of a finish is not to let it go too long without its needed maintenance coat. It’s advisable to give the home a walk-around once per year and inspect the integrity of the finish, especially on the south, west, or sun-exposed areas. Wash and touch-up the finish as-needed, which on average is 3-5 years on the sun-exposed areas.