A 50-year-old red oak floor, with lots of winter wood and dark grain, needs refinishing. I have received two very different proposals from subcontractors. The first to sand, stain and apply three coats of oil-based polyurethane and the second to sand, apply sodium dichcromate followed by a coat of "hard sealer", water soluble aniline dye, another coat of mahogany tinted PTO hard sealer followed by three coats of uralkyd. Can someone explain these two finishing techniques? I like the sample of the second proposal, but the price is much higher. How can I achieve the smoother, more natural finish of the second proposal more economically?
From contributor B:
The first proposal is a standard procedure to a floor finish/refinish job. The second one is more complex and time-consuming, thus the difference in price. The "sodium dichromate" is a little different approach. Normally, potassium dichromate is used for a chemical change of color. The second step you mentioned is a hard sealer. This would seal in that color caused by the dichromate. What's confusing to me is the water-soluble aniline dye that is applied. I don't understand how this will work, but evidently it does. What that says is that a color dye is applied on top of the chemical dye color that has been sealed in with a "hard sealer". So this winds up with a different color from the chemical first color. Then a "toner" of mahogany made up of the hard sealer is applied--this adds more color in a small amount and evens out the overall color. Then all of this is topcoated with 3 coats of uralkyd (probably a polyurethane, either solvent or water base). I have some questions as to the dye stain application over a hard sealer, but if it works, it works. The second proposal involves more work and most likely looks the best because of the multi-layering process.
I understand the reason you want samples, but realize that the color/look you get from samples made with new red oak will not be the same as the look you get with 50-year-old floorboards, even with a multi-step stain/color process.
There may be other ways to get the richness and depth of color than the sodium bicarbonate, but in order to get the look, multi-layering is necessary to some extent. Dyes are the most-used way of doing this. This guy is using dyes, and evidently he knows about chemical dyes and effects.
Did he do the sample on old flooring or new flooring? Will he get the same base from which to work if the floors are 50-100 years old? Even after sanding. Maybe that's the reason for the chemical dye change. I believe it's going to depend on what the floors look like after the initial sanding to remove existing finish.
2. Isn't this chemical quite hazardous to work with?
If both of my points are so, that would justify the high finishing cost.
Chemical use can be dangerous. He is using chemicals when the floor has to be sanded and the existing finish has to be removed. This takes away the aged (patina) wood, so a newer look appears. If he is trying to match another patina, chemical change could be justified. But dyes can do that also, in most cases. So, getting your color with multi-layer dying will give you the depth that you want. Usually, multi-layer involves sealing each color, sanding or screening (as long as you don't remove the color) and then sealing as the last step before topcoat. All the sealers and topcoats need to be sanded and compatible. Your last topcoat, of course, does not need to be sanded if all other work is done satisfactorily.
What is hard sealer? I can only guess. I speculate that it means one with a high solids content. What is PTO?
The final finish needs to be very durable so as not to wear through a finish layer and begin wearing down a color layer. Polymerized or not, tung oil finishes are not as durable as other products on the market. I'd explore other options for the topcoat.
Here's what I would do: get an old piece of oak flooring, sand it like the actual floor is going to be sanded. Put a stain on that is the general color you want. I might use dye stain or pigment stain or a combo (like Minwax). Minwax, though I normally don't use it, does a nice job on oak. I would seal this in with a wash coat or very light sealer coat. Then I would tint up my sealer with a color that would bring more clarity and depth. This also aids in making the overall look more even. (There might be some areas darker or lighter than others.) Then I would use a full sealer on top. This sealer can aid in the filling of the pores that oak has. Screen this well and vacuum dust up very well. Then lay down my topcoats (notice, more than one), smooth out between coats to knock down nibs and such.
Most floor finishers have solvent finishes. If the quarters are occupied, I would not hesitate to use a water borne product. Van Technologies has a wb product that I am sold on for flooring. The best part is, if in a few years it needs to be restored, all one has to do is sand out scratches and apply another topcoat without having to go to bare wood, unless of course the color is to be changed. It's a crosslinking urethane and when it's cured it's very hard. Several coats will fill in the pores to the smoothness that the owners are looking for. It has a high solids content.
Comment from contributor J:
Potassium Dichromate is toxic to the user. An alternative non-toxic solution to restoring patina to red oak is to pre-treat the red oak with tannic acid and apply a coat of iron acetate. Tannic acid is available in powder form from several internet sources, and can be dissolved in water to form different strengths. Iron acetate will react with the tannic acid to form iron tannate within the wood. Iron acetate can be made by taking 32oz household white vinegar 5% strength and adding 1 fluffed out 0000 steel wool pad in an uncovered plastic container. Let the mixture stand 24 hours, then remove steel wool and filter. Do not cover container because the resulting mixture gives off hydrogen gas. The iron acetate solution can be diluted with distilled water to yield desired look. When applied to tannic acid pretreated red oak, the iron acetate will yield a charcoal gray to ebony appearance, yet when sealed, it will yield warmer brownish/ebony tones. There is no need for the use of dyes with this process.
Pretreatment with tannic acid is not necessary for tannin rich white oak and other tannic acid rich wood species. Pricing sounds reasonable. Standard pricing is ~ $.50/sq ft/application + cost of materials + cost of sanding for finishes of this nature. Hard sealer is a mixture of polymerized tung oil, solvent, and uralkyd resin and is specifically designed for a uralky resin top coat or hybrid pto/uralkyd resin topcoat.