Do I need a primer or an undercoat?

[Yukster]

I want to paint my flat front door which is stained dark brown. The final finish will be light grey. Do I need to apy a priner, an unsmdercoat or both before applying the grey final coat?

 

[sparkwright]

Both.

Sanding first is very important before you start.

You may need to treat any knots first, as they can bleed through paint.

You may need more than one undercoat after priming - because you need to totally cover up all dark areas, and not have any dark streaks (known as grinning).

Your final undercoat should be a nice 'solid' colour.

This way your topcoat should look grin-free.

 

[opps]

Varnish is a pain to paint over. It needs a lot of sanding. Often so much that you will invariably end up sanding through the varnish and hitting the wood. Hence the need for primer.

Unfortunately, in many cases, once you apply the first undercoat you will notice bucket loads of dents that were not visible when the door was varnished. For that reason, I sand away all of the varnish. Once the wood is a uniform colour, I know that it is dent free.

I have no idea if you are planning to use oil or waterbased paints but you can buy waterbased (acrylic) primer/undercoat in grey.

Alternatively, if you only want to buy one product this may be suitable as a primer/undercoat/top coat

https://www.toolstation.com/bedec-multi-surface-paint/p36878

I have never used it and caution you that all waterbased paints will cause the grain to raise (requiring you to sand it back as you go).

 

[Yukster]

Varnish is a pain to paint over. It needs a lot of sanding. Often so much that you will invariably end up sanding through the varnish and hitting the wood. Hence the need for primer.

Unfortunately, in many cases, once you apply the first undercoat you will notice bucket loads of dents that were not visible when the door was varnished. For that reason, I sand away all of the varnish. Once the wood is a uniform colour, I know that it is dent free.

I have no idea if you are planning to use oil or waterbased paints but you can buy waterbased (acrylic) primer/undercoat in grey.

Alternatively, if you only want to buy one product this may be suitable as a primer/undercoat/top coat

https://www.toolstation.com/bedec-multi-surface-paint/p36878

I have never used it and caution you that all waterbased paints will cause the grain to raise (requiring you to sand it back as you go).

Just to clarify the door isn't varnished it's stained

 

[opps]

Just to clarify the door isn't varnished it's stained

Ok.

But it must be more than just wood stain. It may possibly be stained and oiled (or some such).