There is no consensus between professionals about materials and methods used in restoration. In Norway, all paint layers are not removed from old doors or window frames, only the exfoliate paint, which come off easily. The rest paint is left on and a new layer of paint is spread over. This technique was recognized by specialists as low-cost and most careful. Masters should estimate whether the paint must be tamper at all, sometimes it is enough carefully clean the item and then paint it. Another approach is to remove all the paint layers for the first, which will be restored.
Experts do not recommend use hot air dryer for removing paint, if it possible, because the drier damage wood. Also, chemical paint strippers should not be used. If a building part painted with synthetics, it should be removed because it not combines with linseed oil. Experts discovered that the Soviet era floor paint, usually used for painting doors, is not worse at all, until 90-ties years of the 20th century it was produced of the oil-base. Contemporary acrylic and water-based paints were recognized as most unsuitable for old doors and windows. They are very hard to remove, since absorbed into the wood and forming non breathable film.
The most suitable paints for wooden building parts are traditional ones – linseed oil, meal or pitch. They are more expensive than synthetic ones, but are applied in very thin layer, so consumption is far lower. Linseed oil based paints comprise pigment which should beautify and protect the item. To restore an old window frame, it must be cleaned first, then thoroughly varnished with hot linseed oil or varnish (it is the same linseed oil, roasted only), accompanied by turpentine. Brushing paint by sandpaper, the damaged wood upper layer is removed too. The better impregnation wood is more protected. Cover wood up to seven coats, while it absorbs paint.