How To Chemically Strip Wood Floors:
You may find that your wood floor has been sanded to many times in the past, and now is too thin to be sanded again. OR there may be a case that absolutely forbids you to make even a spec of dust (for health reasons or protecting electronic equipment) during the refinishing job, but still, you have to remove all the old finish to do a good job. This article will show you how to use safe, but effective chemicals, to refinish your wood floors.
There are lots of circumstances that make sanding of a wooden floor undesirable. I first ran into one of these when I was asked to refinish a floor in a church.
This job was to refinish the floor area called the sanctuary and the choir stall floors, about 600 sq. ft. The organ pipes were right above this and if the floors were to be sanded and finished the pipes would have to be covered, at great cost. Even covering the pipes would not assure their safety from the sanding dust, and the estimated cost for cleaning the would run into the many thousands of dollars.
I was the only flooring contractor who suggested the floors be chemically stripped instead. I had just finished such a job for one of the church's prominent members and my services came highly recommended. My experience with woodwork stripping included doing about 4 months of work for a friend spaced over several years. I single-handedly stripped about 500-sq. ft. of wainscoting, staircase paneling, banisters, baseboards, door and window surrounds, mantelpieces, and paneled doors. Believe me after tackling all this intricate work stripping a floor is easy. 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. It was here that I developed the multi-stage foolproof method. And as of this writing I have chemically stripped over 5,000 square feet of hardwood floor. This still remains a small but essential part of my business.
I had figured the cost of material to be about $1.25 per sq. ft. (the finish being about only 25 cents of that). The rest of the cost would be labor and hopefully profit.
Here are the steps that I suggest:
1. Determine if your floor can benefit from chemical stripping rather than sanding, is it too thin to be sanded again? Are there large gray areas that won't come clean with the stripping process? You may have to strip the floor first and then sand out the gray spots. Based on the cost of material is your floor worth refinishing this way or would you be better off replacing the floor altogether?
2. Go over the whole floor and set all nails below the surface of the wood, but don't fill them. You can do any repairs now, and sand them flush to make the stripping go easier.
3. Using a safe paint stripper that contains mostly NMP (I'll go into the reasons for this later) like Citristrip ® do a sample patch in a closet or the back of a room to determine how effective this stripper is going to be. You need to go through all the steps I am about to describe, including any staining and finishing of the sample area. Then do a adhesion test by cross hatching with a razor blade, the area of cured finish (2-4 weeks) and apply a piece of duct tape to the area and rip it off. This will assure you of the viability of this stripping method and the compatibility of the finish you want to use. You can apply one coat of finish for this test, but do this test first before you dive into this job.
4. Apply the stripper very thickly to an area of floor that you can easily reach across. You will be working on just so many rows of boards at a time going all the way wall to wall, ending on a specific row. Apply it like you are frosting a cake using a natural bristle brush that has an unpainted handle. I don't use gloves during this process, preferring instead to coat my hands with a barrier cream like Hand Guard ®. But I don't touch the stripper, or allow it to get on the handles of any tools. This I believe is safer as it keeps me alert to the danger of skin exposure and allows more dexterous use of the tools. I will always wear a long sleeved shirt, and a butyl rubber apron. Using the brushwork it into the floor, smushing it right down to the ferrule. Recoat any areas that seem to have dried up. For the average floor finish removal, a gallon of Citris Strip ® will do only about 100-sq. ft. of floor. So don't be afraid to pour on lots. Wait about 15 minutes and smush it in with the brush again, reapplying any bare spots that might have shown up.
5. Wait about another 15 minutes and this time use a good quality filling knife to work the stripper without scratching the wood. I use a 2" and 3" wide filling knife that has a ground tapered blade that is 5" long. This is the proper tool for the job and it will not scratch the wood like an ordinary putty knife will. Work the stripper at least twice with the filling knife waiting 15 minutes for the stripper to do it's work each time. Add more stripper between working it with the knife, and even out the coating each time also. You want the stripper to spend the maximum time on the finish, leaving no dry spots. By now you should be feeling the bare wood beneath your filling knife and not the slippery top of the left over finish. You will know by doing the test patch if you have to repeat this process and have some prediction as to the amount of stripper it will take to get to the bare wood.
6. When you're sure you've loosened all the finish you now have to remove the stripper. I scoop up the used stripper with a 6" wide drywall taping knife, any brand will do but the better knives also have a ground tapered blade. Use the filling knives to assist in scooping and put it in a waiting bucket. So far I haven't used gloves and have kept the handles of all the tools clean.
7. There will still be some residual stripper left and I do a final scrubbing of the floor with nylon rubbing pads. The least expensive ones I find at my local supermarket. They are the green flat square pads made for pot scrubbing. These are abrasive enough to assist in the final removal but won't scratch the wood, and will absorb most of the remaining stripper. I don't touch the pad because I have a handle that has little knobbies that keep it in place while I scrub the floor vigorously with the grain of the wood.
8. Next using a plastic chemical wash bottle filled with odorless mineral spirits. I soak the floor a small section at a time and scrub with a clean pad, turn over the pad and keep scrubbing until the area comes clean. If you have done everything right so far, it will only take a few pads to do 20 sq. ft. I cut each pad to fit the handle exactly.
9. For the next step you now need to don good quality butyl rubber gloves, and if you can find them, cotton liners to absorb the sweat.
10. Continue to soak the floor but now remove the solvent with paper towels. I soak the whole area I'm working on and roll out the towels to absorb the mineral spirits as they lay flat on the floor. Try to blot the solvent up. You will know when all the goop is off the floor when your white paper towels come wet but clean. Expect to use a lot of paper towels. Use the wash bottle to irrigate and remove any stripper that may have gotten stuck in gaps or holes.
11. Repeat this process row by row until the whole floor is done. I never do more than about 100 square feet per day. Then let the whole floor dry for 2 days. Don't walk on it much as it now has no protection from water or dirt. And don't smoke or strike a match around this solvent laden floor, else you will have no floor and no house.
12. When the floor is dry it should be quite a bit lighter in color unless it was previously stained. The stripper will not remove a dye or pigmented stain. All this solvent may have raised the grain a bit giving the floor a rough hairy appearance. This can be easily removed with a gentle sanding by hand (try a drywall pole sander) or if you have a large area you can rent a floor buffer and with a 100 grit screen disk polish the surface smooth again.
13. If the floor has darkened with age I sometimes apply a medium dark stain to the floor that helps even out the overall color. The Behr ® brand Oilwood pigmented stain, is quite easy to use, and can be applied several times to deepen and adjust the color. Or try Watco ® or Deft ® oil stain finishes. Because of their asphaltum base will show old sanding marks the least. Let these stains dry and apply 3 coats of polyurethane (oil based) finish scuff sanding and cleaning between coats. I've got a great article on "How to Apply Polyurethane without the Bubbles".
MATERIALS FOR FLOOR STRIPPING
This is the stuff I use mainly because of it's low vapor toxicity. Bear in mind that if this material touches you it will burn in less than a minute. Wash the area affected immediately with soap and water. About a third of it is actually made from orange peel oils and the rest is NMP which is a moderately toxic solvent and has not been shown to cause cancer. It has been shown to cause some mutagenic affects in the next generation of lab mice. So keep pregnant women, or wanting to be pregnant women away from this stuff.
But this is far safer than the methylene chloride strippers, which are confirmed carcinogens, and toxic by breathing, and can cause a change in your heart rate. Methylene chloride is a confirmed human mutagen, it causes changes in inherited characteristics. But don't get even Citristrip in your eyes or you will be in serious trouble. Use odorless mineral spirits instead of regular paint thinner to remove Citristrip from the floor as this low odor varsol or naphtha (as it's also called) is a bit less toxic to breathe. Contact Citristrip or use the link below to purchace from Amazon.com
These are the top quality knives still made and sold in England. A regular putty knife simply won't give you the control. These filling knives will keep your knuckles out of the goo, because of their length and flexibility. I found that they had the least tendency to scratch the bare wood surface, even when working against the grain. The secret is in the ground taper in the blade, you would not believe the difference over those 5 dollar putty knives. These cost 15 or more USD and are worth every cent, even their walnut handles feel comfortable after hours of use. You can order these fine tools through various British tool suppliers, and I'll give you one to get started at http://www.decoratingdirect.co.uk/Tools/Knives_Scrapers_and_Blades/
It is preferable to use chemical wash bottles, that you gently squeeze the solvent through it's spout. These bottles will hold up against most all solvents and they are so simple they will never fail. Does the best job at irrigating the goop out of those gaps. I tried sprayers in the past but beside filling the air with fumes when the solvent is misted they all failed when the mineral spirits melted their inner parts. The 500-ml. size is available through Efstonscience 888-777-4581 or http://www.E-SCI.com. The product is called Fisherbrand ® polyethylene wash bottle 03-409-22C, from Fisher Scientific
SCRUB PADS ETC.
You will be using lots of these, so seek them out at the bulk section at supermarkets. The best are the flat green 6" by 9" pads I find at Loblaws in Canada, you'll have to scout out your own, keep an eye out for them when you grocery shop. There are more expensive ones made by 3M at woodworking shops. They are used to rub out finishes but are far too costly for this purpose. Steel wool, I found to be not absorbent enough and couldn't be held with the knobbie handle I suggest you buy for the flat pads. Remember you must keep your fingers out of the stripper. And as for the paper towels, you are going to use lots. It's typical to use 6 rolls to mop up each 100 square feet of floor, so look for them on sale a couple of weeks before you do the job, and buy more than you think you need.