Hi,

I have recently been doing some window woodwork gloss painting with
crown one coat gloss, decided I needed to do anothe coat, as the brush marks
at the stat of the stroke were showing. Sanded and rubbed down with white
sprit, noticed some parts were blistered, rubbed with the cloth a little
more and large amounts came off. The paint had been applied about 60 hrs
before.

Any idea what migh have gone wrong?

Thanks

"James Salisbury" wrote in message
...
Hi,

I have recently been doing some window woodwork gloss painting with
crown one coat gloss, decided I needed to do anothe coat, as the brush
marks
at the stat of the stroke were showing. Sanded and rubbed down with white
sprit, noticed some parts were blistered, rubbed with the cloth a little
more and large amounts came off. The paint had been applied about 60 hrs
before.

Any idea what migh have gone wrong?


AFAIK there is no chemical reaction occuring when gloss paint dries. All
that happens is the oil evapourates. Therefore soluble in white spirit
before == soluble after.

When emulsion dries a polymerisation chemical reaction occurs. Just like the
formation of many plastics, so what you get after is not just a solid
version of what was in the tin. Although it is water based, the product of
the polymerisation is not water soluble.

HTH

--
Mike W

When emulsion dries a polymerisation chemical reaction occurs. Just like
the
formation of many plastics, so what you get after is not just a solid
version of what was in the tin. Although it is water based, the product
of
the polymerisation is not water soluble.

HTH

--
Mike W
Hiya Mike.
Thanks for that, I think I'd figured the first part myself, but that last
bit I didn't realise.

jim.

You must have run the top of the paint off when you opened it and not
stirred it all in. I can't think of a reason for what you have had
happening. You aught to know that a skin forms on a part tin of paint
and that it is insoluable. It oxidises into a thermosetting plastic on
contact with air.

Paint consists of an oxidiser, powdered colourant and a vehicle. The
oxidiser is often tunge oil or a synthetic resin like it and the vehicle
is solvent -usually white sprit. The powdered colour is often metal salt
or oxide. It can also be organic dye.

There is no way that a full compliment of the above from a reputable
source will behave as you say it has.


--
Posted via Mailgate.ORG Server - http://www.Mailgate.ORG

On Sat, 02 Oct 2004 14:59:18 GMT, "VisionSet"
wrote:



"James Salisbury" wrote in message
...
Hi,

I have recently been doing some window woodwork gloss painting with
crown one coat gloss, decided I needed to do anothe coat, as the brush
marks
at the stat of the stroke were showing. Sanded and rubbed down with white
sprit, noticed some parts were blistered, rubbed with the cloth a little
more and large amounts came off. The paint had been applied about 60 hrs
before.

Any idea what migh have gone wrong?


AFAIK there is no chemical reaction occuring when gloss paint dries. All
that happens is the oil evapourates. Therefore soluble in white spirit
before == soluble after.

When emulsion dries a polymerisation chemical reaction occurs. Just like the
formation of many plastics, so what you get after is not just a solid
version of what was in the tin. Although it is water based, the product of
the polymerisation is not water soluble.

HTH

Don't get this....so why doesnt gloss come off whenever you rub it
with white spirit ? We'd all be using it as stripper wouldn't we ?

"norm" wrote in message
...



AFAIK there is no chemical reaction occuring when gloss paint dries. All
that happens is the oil evapourates. Therefore soluble in white spirit
before == soluble after.



Don't get this....so why doesnt gloss come off whenever you rub it
with white spirit ? We'd all be using it as stripper wouldn't we ?

Okay, so I'm wrong, more certain of the emulsion description though.

--
Mike W.

VisionSet wrote in message ...


"norm" wrote in message
.. .



AFAIK there is no chemical reaction occuring when gloss paint dries.
All
that happens is the oil evapourates. Therefore soluble in white spirit
before == soluble after.



Don't get this....so why doesnt gloss come off whenever you rub it
with white spirit ? We'd all be using it as stripper wouldn't we ?

Okay, so I'm wrong, more certain of the emulsion description though.

Er, don't think you're 100% right about that either :-). Dispersible in
water before = water sensitive after i.e. won't stand prolonged contact
with.
If they could get the emulsifiers to disappear during drying, water based
paints would truly have arrived. Ammonia does that but would be worse than
solvents for the user.
IIRC they dip some new cars in acrylic paint but in the kind of controlled
environment that isn't possible for d-i-y.

"VisionSet" wrote in message
...

AFAIK there is no chemical reaction occuring when gloss paint dries. All
that happens is the oil evapourates. Therefore soluble in white spirit
before == soluble after.
Mike W

Oil-based paints contain linseed oil which has unsaturated (ie double)
carbon bonds. These react with oxygen in the air and slowly cross-link
forming a polymer.
That's why you get a skin in a partly-used tin of paint. The air-gap will be
fully saturated with solvents within minutes of replacing the lid (so no
more evaporation occurs) but there's enough oxygen for the surface paint to
react with.

I've never known white spirit to dissolve dried oil paint. Maybe it was
brush cleaner?

--
LSR

On Mon, 04 Oct 2004 10:52:17 +0100, Laurie wrote:

"VisionSet" wrote in message
...

AFAIK there is no chemical reaction occuring when gloss paint dries. All
that happens is the oil evapourates. Therefore soluble in white spirit
before == soluble after.
Mike W

Oil-based paints contain linseed oil which has unsaturated (ie double)
carbon bonds. These react with oxygen in the air and slowly cross-link
forming a polymer.
That's why you get a skin in a partly-used tin of paint. The air-gap will be
fully saturated with solvents within minutes of replacing the lid (so no
more evaporation occurs) but there's enough oxygen for the surface paint to
react with.

I've never known white spirit to dissolve dried oil paint. Maybe it was
brush cleaner?

After 60 hours (OP said) this seems extreme.
The evaporation of the solvent (White Spirit, Water or Xylene) is what
makes the paint become touch dry.
The polymerisation is what makes the paint film permanent.
This is hours for Vinyl and Acrylic.
This is a day or so for Polyurethanes and Alkyds
This weeks for the resin in Hammerite.

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html

"Ed Sirett" wrote in message
news
On Mon, 04 Oct 2004 10:52:17 +0100, Laurie wrote:

"VisionSet" wrote in message
...

AFAIK there is no chemical reaction occuring when gloss paint dries.
All
that happens is the oil evapourates. Therefore soluble in white spirit
before == soluble after.
Mike W

Oil-based paints contain linseed oil which has unsaturated (ie double)
carbon bonds. These react with oxygen in the air and slowly cross-link
forming a polymer.
That's why you get a skin in a partly-used tin of paint. The air-gap will
be
fully saturated with solvents within minutes of replacing the lid (so no
more evaporation occurs) but there's enough oxygen for the surface paint
to
react with.

I've never known white spirit to dissolve dried oil paint. Maybe it was
brush cleaner?

After 60 hours (OP said) this seems extreme.
The evaporation of the solvent (White Spirit, Water or Xylene) is what
makes the paint become touch dry.
The polymerisation is what makes the paint film permanent.
This is hours for Vinyl and Acrylic.
This is a day or so for Polyurethanes and Alkyds
This weeks for the resin in Hammerite.

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html



I think I may have a partial answer,

I was overpaiting old gloss. The previous top layer of old paint came off
very very easly, ie with the push of a filling knife it came off in big
sheets. I suspect that I may have found a patch that had'nt taken to the old
paint undeneath, and the mechanical action of the cloth (tescos cheap
dishcloth) helped it off.