Hello Steve. I am the "newbie" of the group (just signed up yesterday), but will take a stab at helping you out.
As was eluded to above, nowhere is the adage "you get what you pay for" more true than when it comes to exterior finishes. Trying not to be too partial, Sikkens is an excellent exterior wood finish and although not the least expensive finish, it more than pays for itself in greatly reduced maintenance intervals and very easy maintenance if done properly. Another product showing promise is Fuhr Industrial's 260.
A few things to keep in mind when dealing with exterior finishes:
> as is true with most finishes, proper surface preparation plays as important a role as choosing the right finish.
> using a clear finish alone (ie no stain, etc.) is asking a lot of the finish itself, and although there are some great clear "spars", you will likely pay a lot for them. This is one of the many reasons Sikkens performs so well, because the majority of their finishes have colorfast pigments suspended in them.
> using a conventional stain in an exterior application is typically not a good idea – even if you use a high performance clear topcoat. The reason is that the majority of pigments used to color these stains do not hold up well to uv exposure. And although the topcoat will (or absolutely should) include UV inhibitors and may hold up very well, some uv will still make its way to the stain and begin fading it out.
> There are essentially two types of exterior finishes – film build and penetrating. All else being equal, film build provides the longest lasting and most durable finish. They also offer various sheen options. The drawbacks are they are more unforgiving when it comes to surface prep and application, multiple coats are required, and the material and total system costs more. Conversely, penetrating finishes typically costs less and are easier overall to apply. These are typically single-coat systems (basically give the wood all it will take, and no more). At the same time, they aren’t as durable, dry to a flat finish, and require more frequent maintenance intervals
> don’t use a film build finish where poor ventilation and/or excess moisture is present (a good example would be if any part of your cross comes into direct contact with the soil). Film build finishes are designed to breathe but only to an extent. When subjected to excess moisture, the film can’t breathe fast enough and moisture will accumulate under the finish and eventually delaminate if from the substrate. You are much better off going with a penetrating oil in this sort of application.
Of course, there is a little more to it than this, but I hope this helps answers your original question.
Good luck with your project!
