Removing finishes from wooden floors
It can be necessary to remove existing floor finishes (varnish, wax, oil, polish) especially before wooden floorboards are sanded (sanding the floor without removing the original may clog the abrasive and make sanding take longer and be more costly) or if a new type of finish needs to be applied.
The biggest problem is knowing exactly what the previous finish was as each specific type will have its own technique and solvent. The notes below are for general guidance, always start by stripping a small area of the floor to make sure that the technique being used actually works on the particular floor finish.
Safety: White Spirit and oil or resin based finishes are highly flammable. Always provide as much ventilation as possible, make sure that there are no naked flames in the area of work (including oft forgotten exposed pilot lights and sparks from electric motors) and that all contaminated materials are disposed of, or cleaned, safely.
Never try to clean a floor around furniture in the room, remove everything so that you have a clear areas to work in.
Any old paint or varnish finish can be stripped using a suitable chemical paint/varnish stripper. This can be expensive (a large floor will need a lot of chemical strippers), time consuming and messy. Refer to the manufacturers instructions for using the stripper and pay particular attention to any precautions and ventilation requirements specified.
Special attention will need to be paid to ensure that the chemical is completely removed from the wood, or neutralised before applying a new finish, otherwise there may be a chemical reaction with the new finish.
Even after using a suitable chemical paint/varnish stripper, the timber will need to be sanded to prepare the surface.
One advantage of using a chemical paint/varnish stripper is that the abrasive used for the sanding should last longer; without removing the varnish any abrasive will become clogged with the varnish.
Any old oil, wax or polished finish can be removed before sanding by initially rubbing with a cloth soaked with white spirit and then scrubbing the floor timbers using steel wool and white spirit. Working in small areas, work the white spirit into the finish to soften it. As the finish becomes softened, lift it using a scrapper (drop the goo either into an old paint tin or onto old newspapers) and then use cloths dampened with white spirit to left the remaining finish.
It is important to ensure that an appropriate respiratory mask and gloves are used together with adequate ventilation of the working area as the fumes from white spirit are harmful.
This is time consuming and messy, but varnish will not cover any of these finishes, just sanding them without first removing as much as possible will just clog the abrasive and possibly 'drive' the old finish further into the wood grain.
Once as much of the original floor finish has been removed, and the floor allowed to thoroughly dry, the floor will need to be sanded.