Saving The Finish

Applying over an oily surface, or over certain exotic woods—like rosewood, teak, ebony, and cocobolo—that contain natural oils. Buy the same supplies needed for light polyurethane scratch repair (mineral spirits, brush, tack cloths, polyurethane, steel wool) with two exceptions – you’ll also want very fine sandpaper and a wood stain that matches your hardwood floor. And there is also the question of how ‘easy’ it is to remove the (supposedly easily) ‘removable’ solvent-based acrylic varnishes. A © inch thick hardwood floor has a wear surface, the thickness above the tongue, of a little over © inch thick. Finishes shrink as they dry and surface tension makes the finish shrink away from the edges towards the center.

When your hardwood floor needs to be cleaned beyond what a vacuum can do, you need to know what type of floor top coat or finish you are trying to clean. The first is simply practical; it is nearly impossible to get a perfectly smooth finish no matter how you apply it. Even in a dedicated clean room, the odds against getting a finish to dry without picking up dust nibs are astronomical, and for those of us who finish in our wood shops, the odds are even worse. Sealers are brush-on liquids that penetrate into the wood to limit the amount of absorption.

It is a plastic so tough that hardly anything can penetrate it. In addition to this exceptional durability, polyurethane is easy to put on; fairly fast-drying; super-resistant to chemicals and water; and available in low-gloss, satin, and high-gloss finishes. Most are water-based and are designed to only remove the wax or maintenance topcoat finish without affecting the underlying sealer.

The factory sealer was probably poly-based, so I’d expect compatibility issues with my nitrocellulose topcoats I needed to seal the wood to ensure that the nitro would stick without peeling or lifting later on. I’ve often used shellac for this, but recently I’ve started using ColorTone waterbase sealer because it goes over everything except oils, and it’s compatible with nitro.

With all older varnishes (and some newer ones!) it becomes more and more necessary to remove the old varnish because it has begun to degrade in some way: 1, discolouration – not just yellowing, but actually going brownish in some cases; 2, cracking or other physical failures; 3, dust intrusion and other contamination; 4, changing chemically and becoming harder to remove, forcing the need to use stronger solvents that pose more of a risk to the paint layer.


These days I stain in the sunburst with water based wash and finish with nitro, a process that takes many weeks to cycle, but my return customers are not only willing to wait, they demand it. Their musician’s ears (not a highly trained and ticketed professional technician’s ears) know exactly what they are hearing, and what they are hearing is a better tone and sustain from thin” nitro finishes.

Hi – Im moving into a house with old hardwood floors – they have previously been coated with poly but hat has since turned rather yellow and very much worn away in many places – I have sanded my floors down back to the wood but now I dont know how to finish them – I prefer the look of paste wax buffed floors and I have all the equipment to do that, I just dont know if I need to put something on the raw wood before waxing.

If that does not do it, again try in an obscure spot first, but mineral spirits (paint thinner) – though that WILL soften polyurethanes so use a quick dabbing towards center technique with thinner-wetted paper towel (or with Q-tip for small spot), and after each pass wipe with dry paper towel scrap to remove any free thinner – again, always wiping toward center of the contaminated area.

Before you start confusing this with sand, walnut shell, steel shot, glass bead blasting educate yourself and understand the very different physics that results in the paint being stripped through soda blasting (sodium bicarbonate AKA a course baking soda) in really simplified terms the energy released from the soda exploding as it contacts the surface is transferred into the finish causing it to release… okay maybe too simplified.

Humidity, temperature changes, species of wood and coarseness of the grain… even the manner in which it was kiln-dried can have a devastating effect on your attempts to get the finish just right. It is more important on the second and final coat, to prevent brush marks from appearing across the wood grain. You might want to consider applying your finish coat using a spray can poly varnish.

Well you could just spray more lacquer in that one area and blend it in. But I’m not sure if that will make the spot look better or worse, since you’ll be laying more finish that you’ll likely burn through again. The best thing you could have used to get the polyurethane off is a methylene chloride paint remover but it certainly wouldn’t make the nontoxic, nondangerous criteria and are quite the opposite.

This serves as a great alternative to a paintbrush because it applies the finish more evenly, reducing the chances of bubbling. Unfortunately, if your finish is chipping away from the stain on a floor, you will likely be resanding the floor. You will thin out the coverage and the polyurethane floor finish will tack up on you sooner. I priced the church job at $4 per sq. ft. As I was the only viable proposal, I won the contract to strip and finish the floor with 4 coats of polyurethane. Ideally, the condition of your floors sound like they would benefit from refinishing – scuffing or sanding and applying a new finish.