Checking and Preparing the Surface
New Wood
All wood that has not been treated - from flat-pack furniture to floorboards - is prepared in the same way:
- sand it lightly with 180 grit/240 grit sandpaper
- remove all dust with a vacuum cleaner
- wipe with a cloth moistened with white spirit to remove any traces of grease
If the wood has a lot of knots or is very resinous (oozing sap), the affected areas should first be sealed with knotting solution, which can be brown or colourless. Use a colourless version if you want to apply a translucent finish on top. Applying knotting solution will affect the wood's ability to absorb wood dye and it may be incompatible with some finishes, so make sure you check the manufacturer's recommendations.
The wood is now ready for one of these treatments:
- varnish, oil, or wax
- paint
- colour with wood dye or stain followed by varnish, oil, or wax
- colour and finish with an all-in-one product
Finished Surfaces - Good Condition
A finish in good condition is fulfilling its protective role and is best left intact if possible. If you want to change the appearance, consider these options.
- Most varnishes can be painted over (check in an inconspicuous place to make sure there is no incompatibility).
- Colourless and light varnishes can be recoated with a coloured varnish. You can apply acrylic varnish over polyurethane varnish and vice versa as long as the old finish has completely cured - two weeks for acrylic varnish, one month for polyurethane varnish. Just sand lightly to provide a good surface for the new finish and remove dust and grease as above.
- Painted surfaces can be overpainted with a different colour.
- With French polish, oil, and wax finishes you can only apply more of the same. If you want to alter the appearance radically, these finishes must be stripped back to the bare wood.
Finished Surfaces - Poor Condition
- Cracked, blistered, or flaking finishes are usually found on exterior woodwork and garden furniture.
- Remove all the loose finish. Use a shavehook and work with the grain, pulling the tool towards you.
- Rub down with sandpaper.
- Use dampened wet-and-dry sandpaper if the paint might contain lead.
- Leave any paint or varnish that is hard to remove unless there is a marked step between the surface of the sound paint and the exposed wood.
- If there is more paint than wood visible, filling may be a better option than stripping.
- Oil and wax finishes can be revitalized with several new applications of the same finish.
