Hello,

I've just built some shelving using MDF and have just encountered some kind
of paint incompatibility the like of which I have never seen before.

Specifically I primed the shelving with Homebase own brand wood and metal
primer (oil based)....but when I try to apply a top coat the paint has been
repelled as if I am trying to paint wax!! On this occasion the top coat is
Farrow and Ball "Modern Emulsion"...which is water based and 'kin expensive.

Pic he http://www.hernibles.com/paint_small.jpg

What really puzzles me is that the same paint combination on bare wood just
works with no problem at all.

What the heck is going on?

David

Vortex wrote:

I've just built some shelving using MDF and have just encountered some
kind of paint incompatibility the like of which I have never seen before.

Specifically I primed the shelving with Homebase own brand wood and
metal primer (oil based)....but when I try to apply a top coat the paint
has been repelled as if I am trying to paint wax!! On this occasion the
top coat is Farrow and Ball "Modern Emulsion"...which is water based and
'kin expensive.

Pic he http://www.hernibles.com/paint_small.jpg

What really puzzles me is that the same paint combination on bare wood
just works with no problem at all.

I had just the same problem a few years ago when using Leyland acrylic
(ie water-based) gloss over an oil-based primer. Also on MDF, but it
was just the same problem where the substrate was timber.

I posted a similar "WTF?" plea for help here too, which you might be
able to locate(!) IIRC the advice was not to mix'n match oil- and
water-based paints, something which I've always made a point of adhering
to since then, and have not had a problem again.

Still don't understand why it should happen though, if the underlying
coat is fully dry.

David

"Lobster" wrote in message
...
Vortex wrote:

I've just built some shelving using MDF and have just encountered some
kind of paint incompatibility the like of which I have never seen before.

Specifically I primed the shelving with Homebase own brand wood and metal
primer (oil based)....but when I try to apply a top coat the paint has
been repelled as if I am trying to paint wax!! On this occasion the top
coat is Farrow and Ball "Modern Emulsion"...which is water based and 'kin
expensive.

Pic he http://www.hernibles.com/paint_small.jpg

What really puzzles me is that the same paint combination on bare wood
just works with no problem at all.

I had just the same problem a few years ago when using Leyland acrylic (ie
water-based) gloss over an oil-based primer. Also on MDF, but it was just
the same problem where the substrate was timber.

I posted a similar "WTF?" plea for help here too, which you might be able
to locate(!) IIRC the advice was not to mix'n match oil- and water-based
paints, something which I've always made a point of adhering to since
then, and have not had a problem again.

Still don't understand why it should happen though, if the underlying coat
is fully dry.

David

The primer was applied 24 hours ago. BUT dried in a chilly garage
overnight, so not completely dry.

I'm just going to have to wait for the emulsion to dry and see how well it
has adhered. Have a hunch I'll have to sand it all down and start again.

I'm so disillusioned I think I'll go to the pub.

D

On Sun, 28 Oct 2007 11:43:15 GMT, Lobster
wrote:

Vortex wrote:

I've just built some shelving using MDF and have just encountered some
kind of paint incompatibility the like of which I have never seen before.

Specifically I primed the shelving with Homebase own brand wood and
metal primer (oil based)....but when I try to apply a top coat the paint
has been repelled as if I am trying to paint wax!! On this occasion the
top coat is Farrow and Ball "Modern Emulsion"...which is water based and
'kin expensive.

Pic he http://www.hernibles.com/paint_small.jpg

What really puzzles me is that the same paint combination on bare wood
just works with no problem at all.

I had just the same problem a few years ago when using Leyland acrylic
(ie water-based) gloss over an oil-based primer. Also on MDF, but it
was just the same problem where the substrate was timber.

I posted a similar "WTF?" plea for help here too, which you might be
able to locate(!) IIRC the advice was not to mix'n match oil- and
water-based paints, something which I've always made a point of adhering
to since then, and have not had a problem again.

Still don't understand why it should happen though, if the underlying
coat is fully dry.


Is MDF coated with anything?
When I worked in a car bodyshop, we used to get problems sometimes
with silicones in the old paint causing the new paint to pucker.

Vortex wrote:

"Lobster" wrote in message
...
Vortex wrote:

I've just built some shelving using MDF and have just encountered
some kind of paint incompatibility the like of which I have never
seen before.

Specifically I primed the shelving with Homebase own brand wood and
metal primer (oil based)....but when I try to apply a top coat the
paint has been repelled as if I am trying to paint wax!! On this
occasion the top coat is Farrow and Ball "Modern Emulsion"...which is
water based and 'kin expensive.

Pic he http://www.hernibles.com/paint_small.jpg

What really puzzles me is that the same paint combination on bare
wood just works with no problem at all.

I had just the same problem a few years ago when using Leyland acrylic
(ie water-based) gloss over an oil-based primer. Also on MDF, but it
was just the same problem where the substrate was timber.

I posted a similar "WTF?" plea for help here too, which you might be
able to locate(!) IIRC the advice was not to mix'n match oil- and
water-based paints, something which I've always made a point of
adhering to since then, and have not had a problem again.

Still don't understand why it should happen though, if the underlying
coat is fully dry.

David

The primer was applied 24 hours ago. BUT dried in a chilly garage
overnight, so not completely dry.

I'm just going to have to wait for the emulsion to dry and see how well
it has adhered. Have a hunch I'll have to sand it all down and start
again.

I'm so disillusioned I think I'll go to the pub.

D

I'd guess the problem is simply that the oil based primer wasn't fully
dry. If you've put a water based paint over it, that may well dry over
the top and slow the solvent evaporation from the undercoat.
I'd put the shelving indoors for 24 hours, then sand quite aggressively
with 180 grit, and try the F&B coat again.
The problem is likely to be more pronounced on MDF because the faces
aren't as porous as wood and the undercoat is sitting on the surface.

Vortex wrote:
Hello,

I've just built some shelving using MDF and have just encountered some
kind of paint incompatibility the like of which I have never seen before.

Specifically I primed the shelving with Homebase own brand wood and
metal primer (oil based)....but when I try to apply a top coat the paint
has been repelled as if I am trying to paint wax!! On this occasion the
top coat is Farrow and Ball "Modern Emulsion"...which is water based and
'kin expensive.


Use farrow and ball oil based paint. Same colors.

Next time, don't prime. Just use emulsion.

Pic he http://www.hernibles.com/paint_small.jpg

What really puzzles me is that the same paint combination on bare wood
just works with no problem at all.

What the heck is going on?

David

On 29 Oct, 01:01, The Natural Philosopher wrote:
Vortex wrote:
Hello,

I've just built some shelving using MDF and have just encountered some
kind of paint incompatibility the like of which I have never seen before.

Specifically I primed the shelving with Homebase own brand wood and
metal primer (oil based)....but when I try to apply a top coat the paint
has been repelled as if I am trying to paint wax!! On this occasion the
top coat is Farrow and Ball "Modern Emulsion"...which is water based and
'kin expensive.

Use farrow and ball oil based paint. Same colors.

Next time, don't prime. Just use emulsion.

Quite - old decorator's trick, if you've run out of wood primer
(emulsion makes a crap primer on metal, though)

Edward