Refinishing a front door - Just the basics
From time to time the clear finish on a front door will fail, due mainly to the ultraviolet of sunlight breaking down the clear coating and the wood fibers underneath. A painted door will also fail, the paint cracking and peeling. If you let it go too long, rot can develop, usually on the bottom edge. Treating rot on the bottom edge of a door will be covered in a separate application note.
There is a way to get a longer-lasting clear or paint finish on a door. It involves surface preparation, and the right kind of clear primer, and the right kinds of topcoats, and the correct application of the topcoat. This application note is about priming for either a clear finish or any paint, preferably oil-base enamel paints. Clear finishes and doing a good varnish job are covered in separate application notes: This one is just about the surface-prep and priming.
The door is best refinished if you take it off its hinges and do the work in your shop, garage or basement work-area with the door horizontal, but it is possible to do the work when the door is vertical, hanging on its hinges.
Let's start by sanding the wood back to a clean surface, removing all the old finish. 50-grit and a palm sander applied gently to the wood will cut the old flaking finish quickly, and you can then change to 100-grit for a final sanding. Brush off the wood dust that will be stuck to the surface. A stiff bristle brush may be helpful.
Assuming there is no rot to deal with [that's a separate topic] and assuming that we don't need to stain the wood [that's another topic], the next step is to apply Smith's Clear Penetrating Epoxy Sealer™. This is unlike any other epoxy product on the market. It is permanently flexible, because it is made largely from the natural resins of wood itself. It leaves a porosity in the impregnated wood that is close to the natural porosity of wood, so the treated wood can still "breathe". It is very slow to cure, so when you apply it one day and the first coat of varnish the next day, the Sealer finishes curing under the varnish, and that glues the varnish to the wood with the strength of epoxy glue.
The application may be with a brush or roller, and it soaks into the wood very rapidly. Don't try to apply it like paint, brushing on a thin coat. It is not paint. It is an IMPREGNATING sealer, and so it needs to soak in until it has fully impregnated the wood. This is the important thing, to apply it in one area until it quits soaking in, and then move along. Because it runs like water, the application technique is a little different if the door is vertical. There, you will need to hold a roller only horizontally and roll slowly only upwards; a brush will need to be held with the handle horizontal-to-upwards, so the sealer runs down toward the bristles and the wood.
When the whole door has been saturated with the Clear Penetrating Epoxy Sealer, Let it dry a few days and fully cure. This also gives time for the solvents to evaporate out of the wood. Run your bare hand over the surface; if you feel any rough spots, rub it down with a green abrasive pad, just to take off those bumps. The Sealer sticks to itself and to paint or varnish by chemical bonding; it is not necessary to sand to give "tooth". Just lightly sand to give a surface that feels smooth. Brush or wipe off any dust.
Now, you are almost ready to apply the topcoat. There's one last thing to do, and that is to apply one more coat of the Clear Penetrating Epoxy Sealer, a day or two [only a day in hot weather; one to two days in moderate weather] before you start with the varnish or paint. The reason for this is that the Sealer is very slow to cure [it takes about four days in moderate weather], and we want it to be only partly-cured, ideally, when the first coat of paint or varnish goes on, so it will finish curing under that topcoat and glue it down. It may feel dry to the touch the next day, but it is still slowly curing and can strongly grip paint or varnish within its two-to-four-day cure window.
Using Clear Penetrating Epoxy
Sealer will make any paint or varnish stick better and last longer. Paints
may change, and woods may get softer and weaker, but using Clear Penetrating
Epoxy Sealer before you apply a coating to the wood will glue that finish
to the wood, protecting the wood and increasing the life of any finish.
It’s been around for over 35 years, and that’s one of the things it’s
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