Steve Rainbird wrote:

I don't mind criticism its just rudeness I don't like.

I'd much rather a rude person to a thick one.

Fancy asking such a vague question and not being taken for an effing
ijut. You didn't even specify water based paint. As it happens, I have
seen that washable acrylics are on offer at nearly 1/3rd more a can. I
nearly bought some recently.

You can't wash acrylics so easily as oil based paint. I wasa painting
over some oil based painted cupboard doors. No doubt the stuff I put on
will fail. It was a rush job though and quite effective for the day or
so needed.

Had I time I would have used a PVA base coat. But I had neither time
nor PVA.

I imagine that washable water based paints contain some additive that
allows them to be used in leiu of oil based paints.

Emulsion paints, as distinguished from acrylic paints, are mere
mixtures of oils and water. They are the Trade Paints used in newly
built houses. They can "breathe"; which enables them to go on new
plaster.

Acrylics are similar to emulsions but the oil in them is a vinyl
polymer resin. So I believe at least. I dare say someone here has
delved deeper into it than I. I tend to stop when my fingers get
coated.

Oil based paints will require a base coat -which might be an emulsion
but had best be a vinyl. You then need an undercoat and then the top
coat. The undercoat is the cover and the top coat is the seal.

Before the undercoat can go on, the vinyl must be absolutely dry. It
takes a few hours before the top coat can go on -at least 4 hours after
the undercoat but a day would be better. Then the top coat which needs
a day to dry.

You can get an excellent finish but it is a long job. If these
washables are any good they will revolutionise the trade.

Oil based stuff goes much further than vinyl paint but vinyl paint,
being a thicker coat can get the job done in half a day. You can apply
the second coat as soon as the first is hand dry. (That is, when the
first coat no longer rubs off but the wall is still damp.)

Yer pays yer muny an yer takes yer choices. If you hang on it will come
down in price.
Try and be just a little more specific in your enquiries in the future,
dopey.

*******

As side note, adding something to ordinary acrylic paints will usually
weaken it. PVA for example will allow you to remove it in strips when
dry. I have no doubt there is some additive not dissimilar to PVA in
this new stuff though.

What do they put in exterior paint?
Which reminds me; I used some ordinary white acrylic to paint a reveal
on a front door once. It lasted for years.