Here’s another reader question from a reader and my answer:
“I have a follow up question to your response to a question regarding varnished wooden doors that appeared in the June 2018 (#239) issue of Popular Woodworking. I live in the Texas Hill Country and have a northeast facing alder door that has good overhang protection against water, but it does receive direct morning sun for several hours. The door is about 4 years old and I know for a fact that it was originally finished with Minwax Helmsman spar varnish, which according to you provides little in the way of UV protection.
The finish is beginning to develop a blue-grayish chalking/oxidation, which is rough to the touch. If I wet the surface with mineral spirits, the topcoat returns to clear and transparent while wet. I’d like to know what is the best course of action at this stage? Can I lightly sand and re-coat using a true marine-grade spar varnish with good UV protection, or will I need to do something more drastic?”
Here’s my answer:
I actually restored a front door, recently, with sun deterioration similar to yours but worse.