Sonica Bucksteg, Dulux colour expert,
replies Surfaces must be adequately prepared before painting to provide a ‘key’ for subsequent layers. If the piece has plenty of detail requiring loads of intricate sanding, you can achieve a reasonable ‘key’ by scrubbing the surfaces using steel wool and a sugar soap solution; the steel wool will allow you to get into all the nooks and crannies.
If the existing varnish or paint is in a sound condition (not flaking, peeling or crazing), you can lightly sand the surfaces with 220-grit sandpaper (if smooth) or 180-grit (if scratched or pitted) and follow with 220-grit. Wipe away dust with a damp cloth and wash down with a sugar soap solution; allow surfaces to dry thoroughly. Then apply a primer such as Dulux Supergrip followed by an acrylic PVA or enamel; it’s best to follow through with a particular brand.
For best results:
1 Be aware of ambient temperature – if it’s too hot, paint won’t flow or it’ll dry too quickly.
2 Monitor moisture and humidity as these can affect adhesion between coats. 3 Use a good quality brush! 4 Thin your first coat of colour slightly. 5 Allow each coat to dry thoroughly. 6 Sand lightly with fine sandpaper between coats and also wipe surfaces thoroughly between coats to remove any signs of dust.
Once sanded, previously glossy surfaces should appear dull all over, indicating a slightly etched surface that will hold paint better.