Acrylic over enamel???

We've just bought a house. Built in the early 50's with hardwood Tas Oak skirting boards, architraves and windowframes. The previous owner has painted much of this internal woodwork with an acrylic paint straight over the top of an an enamel paint. This old enamel paint job appears to be a professionally done job as its in very good nick elsewhere in the house.
The acrylic is beginning to scale off in parts and I can easily scrape it off under my fingernail. I want/need to paint these areas again and need some advice on what to do. Do I need to get all this acrylic off so it doesn't peel and flake under the new paint and if so whats the best way to do it. Its a fairly large area so scraping and sanding would take some elbow grease. Or can I just put an enamel sealer straight over the acrylic that will keep it there, then a few coats of suitable enamel semi gloss?

any suggestions much appreciated.
mjr

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Originally Posted by mjr

We've just bought a house. Built in the early 50's with hardwood Tas Oak skirting boards, architraves and windowframes. The previous owner has painted much of this internal woodwork with an acrylic paint straight over the top of an an enamel paint. This old enamel paint job appears to be a professionally done job as its in very good nick elsewhere in the house.
The acrylic is beginning to scale off in parts and I can easily scrape it off under my fingernail. I want/need to paint these areas again and need some advice on what to do. Do I need to get all this acrylic off so it doesn't peel and flake under the new paint and if so whats the best way to do it. Its a fairly large area so scraping and sanding would take some elbow grease. Or can I just put an enamel sealer straight over the acrylic that will keep it there, then a few coats of suitable enamel semi gloss?

any suggestions much appreciated.
mjr

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Worst of it is that the enamel could be lead based if it that old.

I had the exact same problem at my house- I used 3 course sanding pads ( the foam ones) and roughed up the surface it took all the loose acrylic off aswell. Once you have roughed the enamel you can paint it again with acrylic if you like.

If the acrylic isn't stuck putting other paint over the top won't help, the acrylic is still the weak link everything you put over may stick but if the original acrylic is flaking you then have more paint to get rid of as well as having spent time and money in the mean time for nothing.

The only way to ensure future coats stick is to scrape off or at least rub the acrylic if its stuck or is loose you will soon find out. As its not a job you don't want to do often best to do it once properly. The old enamel will be a better base for future coats, if it is flattened off and has lost its gloss. Try the abrasive coated sponge blocks if there is a lot of shape in the timbers.

Scrape or sand off the acrylic whichever works best and if you use sugar soap and scotch brite type pad after you can remove any small traces of the flakey paint and at the same time clean and flatten the enamel gloss.

Lead based paint will only be present if the colours are yellow, orange or red. White, creams, blues, greens, etc don't have lead in them the lead is in the pigment. Undercoats of red lead would be a problem but by the 50's lead had been pretty much replaced with other material in normal house paint.

As you don't intend to remove the enamel lead shouldn't be a problem. If you think you have red or white lead present avoid rubbing it dry.

Putting solvent based enamel over water based acrylic in an effort to improve inter-coat adhesion between the acrylic and the old enamel is a waste of time and money.

What the previous owner should have done is sand and undercoat the old enamel, then apply acrylic. This sort of botch job is often done prior to selling a house in an effort to tart it up a bit.

Really your only choice is to remove the acrylic, then you can undercoat, waterbased is fine, and apply another enamel or an acrylic.

If you are after semi-gloss, the Dulux Aquanamel does a reasonable job, waterbased, low odour and easy to apply.

I'm old fashioned and prefer solvent based semi-gloss enamel, it gives a better finish and is harder wearing, but it smells for a few days and is harder to apply.

Boy, you have some trouble ahead of you. Firstly, if you have unpainted enamel paint ( well I mean without acrylic paint over it), you do not need to sand this before recoating with acrylic gloss, in fact it's better if you don't in case it is lead paint - and white paint may also be lead-based. But what you need to do is wash it with sugar soap to remove grime and then wash it with a grease and wax remover. Then paint it with Zinsser BIN primer or Zinsser Bulleye 123, followed by your acrylic paint.
For the existing acrylic paint it may be easier to remove and replace the woodwork if its easy enough, or else use one of the gel paint strippers and quench the stripping as soon as the acrylic is lifted, then continue a above.

Cheers
Michael

A while ago there was a post on another topic suggesting that there is an external product available for use when you have flaking paint on the outside of your house. It was meant to soak through the old coat of paint and adhear it to the underlying surface. There was no name given but apparently all reasonable paint shops would know about it.

Is anyone aware of this product and would this be an option inside?

Yuk! You have a job ahead of you!

Is the flaking paint really acrylic paint? Or is it one of the cheap nasty vinyl based paints? To find out - saturate a section in methylated spirits - if the paint goes soft and elastic then its a vinyl based paint. Vinyl paints dont sand very well - tending to go rubbery and forming balls on the sand paper. They are also impossible to reliably paint over unless you use more vinyl paint.

I am suspicious becuase its not like modern acrylic paints to behave the way you describe.