Painting.. Is a base coat a must?

[Bud1234]

Hi,
We have done a bit of work in the house. So we have some new plastered walls & some old walls with a bold green colour paint.
My painter says that we dont need a base coat. He is going to do a mix coat first (the paint & water mixed). And then apply the paint on top of it. He says that it should do it.
My worry is that the paint I got is a custom mixed paint from Homebase. We wanted that specific colour on the walls. Will the mix coat be enough to not affect the final finish (in the colour we chose) as we have old funny green colour paint & new plaster (in some areas) on the walls?

Am I clear?

Please help...
Thanks

 

[HERTS P&D]

Mist coat must be applied to new bare plaster or it will come off.

Andy

 

[Bud1234]

Sorry for sounding very ignorant.

So what you say is that the mist coat will not stick to old painted walls?
And we are better off by applying a base coat?

Say the mist coat is applied to the new plaster wall. Will it kill the plaster pink colour enough so that my paint color will not be affected?

Thanks Andy

 

[JohnD]

if you think the existing paint has a strong colour, and the new paint is a pale or different colour, you can apply a mist and a first coat in matt white emulsion, which is cheaper, and will blot out the old colour.

A coat of plain white will also highlight to the eye any remaining blemishes that you need to address before applying the (usually more expensive) final colour, and will remove the need to apply extra coats of the finish colour to hide the old.

the mist coat is needed for new plaster and any filler to soak in and take up the excess absorbency. A mist coat is very thin and you can see through it.