There are many blogs on the internet we feel have been written without experience or just by reading the back of a paint tin, as professional decorators we have tried so many products and processes over the years that we can write with a degree of authority and are happy to share our findings.
Preparing varnished wood for painting
Traditionally varnished wood is difficult to adhere too as most wood varnishes are oil based. We prepare the wood by sanding with a 120 grit sand paper, this is not done to remove the varnish but to remove any little imperfections and more importantly to generate thousands of tiny scratches which act as a key for the primer to grip onto. There is no need to use an electric power sander, doing this by hand is fine, just ensure to get into all the corners etc Once sanded remove any fine dust with a damp micro fibre cloth.
What is the best primer for varnished wood?
Over the years we have tried products such as Zinsser Cover Stain, Zinsser Bullseye 123, Dulux Ultra Grip Primer and a few others. All have varying degrees of success but every now and again we find that after a short period with these products the brown tanning in the varnish can creep through and not all of these products have good opacity so if the varnish is dark you need multiple coats. Some of these products are also not as durable or grip as we as we'd have liked. By far the best results we have had and this is now our go-to product is Tikkurila Otex. It has good opacity so blocks the colour of dark varnish very well, it is fast drying so can be painted over very quickly in just over an hour. The product is oil based but can be painted over with water based paints and has very good adhesion properties.
Cleaning brushes after using Tikkurila Otex primer
This product is oil based so brushes will need to be cleaned with some white spirit first and then a gentle wash through with warm soapy water after. Pro Tip, we always run a combe through our brushes once washed and let them dry, this keeps the bristles straight and in good order for next use.