June 13, 2022

Surface

Most people I talked to about this project were a bit confused about what I was doing; the phrase “staining a fiberglass door” caused a bit of confusion. Plastics and other polymers have found use everywhere for their availability and versatility, and they’re becoming the preferred construction materials for applications that require water resistance. Manufacturers have only recently (the oldest YouTube video you can find on the subject is less than ten years old) begun selling fiberglass doors with embossed wood grain, and it’s a game-changer for those who want the look of stained wood. 

While stained wood appeals to many for its nostalgia and naturalness, it’s not a particularly good material for weathering temperate climates. Its organic fibers attract all sorts of insects and microorganisms, especially during the damp months of a Kansas City spring. Because of its porosity, wood is constantly fluctuating with changing moisture and temperature levels, making it a poor surface for adhesion of the protective coatings required to protect it from the elements. Rather than purchasing a door that would require bi-annual maintenance to avoid discoloration, warping, and cracking, our clients gave material engineers their due and purchased this embossed-grain fiberglass door.

Setup

Extensive preparation was required before beginning the finishing of the door. First, I removed the handle, deadbolt, and weather stripping and masked the hinges. To protect from overspray, I masked floor, frames, and walls on both sides of the door. On the inside, I constructed a sealed plastic containment to keep dust and fumes from floating into the rest of the house. Finally, to exclude the wind-blown bits of tree shed from my finish, I duplicated the containment on the outside.

Stain

First Coat

One of the only advantages afforded by wood’s porosity is its affinity for stain. It will readily absorb and adopt the color of any stain applied to it. Fiberglass, however, is as resistant to stain as it is to water and household chemicals. For finishing fiberglass, craftspeople opt for gel stain, which is designed to leave a residue when wiped off. Achieving dark colors requires multiple applications of stain. Being very viscous, gel stain can take up to several days to cure enough to apply a second coat. With plenty of experience in specialty finishes, our Perry Holloway shared with me a “hot-application” method to significantly cut down that wait time. 

I started with staining the most inconspicuous square to get an idea of how the surface would take the stain. The result of wiping the stain after 5 minutes let me know I needed to let it sit some 20 minutes before wiping.

Using a brush and a lamb’s wool pad, I quickly coated both sides of the door in stain. I went off to eat an apple, then came back to wipe off the tacky stain. To seal in the remaining layer of color, as per Perry’s recommendation, I used aerosol cans to apply a thin coat of varnish.

Second Coat

By the following day, the clear coat was dry enough to be sanded smooth and accept another layer of stain. Our clients were happy with the shade of the door’s inside face and decided to darken the outside face. I applied stain again, gave it a good while to set up, and wiped it off. The second coat provided significantly more color.

Clear Coat

This was the rich Spanish Oak they were going for, and our clients gave the go-ahead to apply the finish. With a handy Graco Magnum X7 (affordable, portable, and powerful enough for any DIY project) I sprayed on a thin coat of spar varnish and headed to lunch. The thin coat quickly “tacked,” i.e., congealed to form a somewhat solid layer.

Over this tack coat, I sprayed a generous layer of varnish. The first coat absorbed solvent out of the fresh coat, accelerating its tacking and minimizing the possibility of sags and runs. 

I carefully pulled down the containment inside but left the outside containment up for a few days while the finish cured.

After the finish coat had cured and the rest of the masking was pulled, our clients had the statement door they were after!