Basically, nothing is really different when renovating old paintwork than when repainting. The only exception: Your paint choice is limited. Because the rule still applies, according to which old and new paint layers should have the same solvent basis. In other words: Apply only synthetic resin paints to synthetic resin paints and only acrylic paints to acrylic paints.
Now to find out, what type of paint is on your renovation object, dip a brush in universal thinner and rub firmly on the paintwork surface. Acrylic paints can be dissolved with it, Synthetic resin paints will defy your efforts.
PREPARATION
First the good news: Old coatings do not always have to be completely removed. Rather, it is important, that you completely remove all loose and poorly adhering parts, in the case of stubborn paint residues, roughening the surface with abrasives or lye is sufficient. Important: The surface must be smooth, there must be no noticeable transitions between the raw wood and the old paint residue.
There are three common methods you can use to remove paint, all of which have their pros and cons. Sanding is undemanding, but dusty, Stripping is quick, stinks but and burning off with the heat gun is convenient, but only works really well with synthetic resin paints. Ultimately, grinding is the most practical thing for you as a Seibermacher, because you roughen up raw wood like old stuck paint at the same time and prepare it for the subsequent painting.
Ein Zwischenschritt bei der Renovierung, which is missing in new coats of paint, is to repair the damaged areas. Especially with wooden doors and windows, constant use leaves its unavoidable nicks, which can easily be snuffed out on this occasion. With the necessary filler you have to use acrylic again- or synthetic resin base (so-called oil spatula) respect, think highly of, which must match that of the new paint. For clear coats, use wood putty in the appropriate color (Nail).
Prank Order
It is advisable in any case for freshening up the paintwork on doors or windows, the wood after the obligatory three-time sanding (grits 60, 80, 120) with a filling undercoat (or also reason for detention) to underline. The special composition of these paints causes, that even the smallest pores and bumps are evened out and the subsequent paint has good adhesion conditions. However, undercoating never replaces a good sanding! You also have to sand the undercoat yourself (240he-grain), namely before the first painting.
It is not uncommon for doors to be decorated with coffers or windows with bars. In this case it is important, to adhere to a certain painting sequence for the individual wooden parts, so that the result is perfect (graphics on the right). With paneled doors, you always start with the paneled profiles, then the cassette surfaces follow, and finally paint the outer frame. Use brushes with plastic bristles for the narrow profiles (Acryllacke) or natural bristle brush (synthetic resin paints), a corresponding role for the surfaces.
When repainting with clear coats, some processes are different. The transparency of the paint requires namely, that you first completely remove all old paintwork, really have to be removed completely, secondly, to get the wood putty to the right color to repair the damaged areas, and thirdly, to sand it perfectly, because the filling undercoat is omitted. In this respect, this variant is more for experienced Seibermacher, above all, If you, as is currently trending, Now you want to trim your doors and door frames, which were previously painted white, to look natural.
In the case of clear coats, pronounced primer coats are unusual. exception: Bona Parquet Varnish Primer, which is only used for sealing wooden floorboards. For the other clear coats, only the primer with a ten percent dilution serves as a sufficient primer.
When working with clear coat, be sure to keep the fact in mind, that insufficient sanding or sanding errors are not concealed by the paint, but rather amplified in their visual presence. Careful work and smoothing, no matter, which paint and which tool you work with, is therefore extremely important.