Moldings enhance the appearance of any room, but selecting the right material for your project can be tricky.
As you start your molding type and material selection process, first consider where the molding is going to be installed and how you plan to finish the molding.
For interior applications, if your objective is to apply a painted finish, your choices would include, from least to most costly, pre-primed finger jointed pine or MDF (Medium Density Fiberboard), paint grade hardwoods such as poplar or lightweight plaster type moldings. Pre-primed moldings are relatively inexpensive, easy to finish and come in a large selection of popular styles / sizes. Many of the more detailed moldings come in the paint grade hardwoods. These moldings require more prep work prior to painting. Plaster type moldings have a look like original plaster moldings found in older homes and are installed using drywall joint compound resulting in a seamless finish. Many large and ornate profiles can be found in plaster type moldings.
If your objective is to see the natural beauty of the wood, you will want to apply a clear finish to the wood, as well as a stain if desired. Stain grade moldings are available in most profiles and can be custom made if required. If the moldings are made from a soft wood such as pine, a wood conditioner is required prior to staining to alleviate uneven coloring. Harder woods are not as prone to this problem. As stain grade woods are more expensive than paint grade, and the installation is less forgiving of inexperienced jointery, it is best to have a professional install these moldings.
Exterior painted applications are typically trimmed with the cellular / PVC moldings (ie: Fipon, Azek) which are able to withstand the elements better than a natural wood product. These products require priming prior to finishing, and a quality exterior finish paint will give the best results.