Painting woodwork - do you sand first?

[BlodwinTheThird]

I need to repaint some door frames and doors. They are gloss at the moment and i want to repaint with white eggshell or satin.

Should I sand first? Some of the woodwork is white, some is royal blue, if that makes a difference.

Yes, you should sand. You need to give the paint something to grip onto, and so the sanding provides this surface. Additionally, gloss paint is especially 'slippery'!

You will need to sand first or the paint won't stick to the shiny gloss.

Sand lightly. You don't need to go mad with it, don't sand back to the wood, but you will need some 'tooth' on the gloss surface. If you're making a colour change, use the appropriate colour undercoat. Even eggshell and satin for wood are pretty thin and transparent, though gloss is more so. A good acrylic undercoat will dry quickly, stick well, and give you a good base for your topcoat, whether that's solvent or water based. It might even be worth using one under whatever colour you put on top.

I'm a fan of solvent based paints for woodwork top coats as a rule, but you do have to be experienced to get a good finish, and the modern acrylics are pretty decent. Personally I always use a solvent-based topcoat, but even I will use an acrylic undercoat a lot of the time.

I've just done this. Lightly sanded down but not to bare wood. One white coat of white undercoat then gloss paint on top. Here is a before and after.

Thank you! All surfaces now sanded - have more or less taken the ‘shine’ off - is that enough?

They will look better if you wipe them down too, I usually use sugar soap and then rinse, gets rid of the grease.

Light sand and undercoat, light sand and then gloss/eggshell. I sometimes do 2 coats. Light sand between each one provides a key and stops chipping.