I know paint technology is a complex science but I usually get away
with it. However, I've been tarting up a pair of old Wharfdale
speakers with spray paint to match the existing grey and black kit and
the finish coat is causing the underlying primer to bubble up on a
small test area.

The primer is "Plasti-kote, Projekt Paint, Primer SUPER" which I
bought from B&Q. I have also bought some Simoniz Acrylic Black as a
top coat. Neither cans give specific details about their chemical
composition but they sure enough don't like each other.

I'm hoping someone can tell me of an intermediate neutral coat I can
apply to avoid having to strip the whole lot back to stage 1.

--
Kind regards,
Geoff Mills

Geoff Mills wrote:
I know paint technology is a complex science but I usually get away
with it. However, I've been tarting up a pair of old Wharfdale
speakers with spray paint to match the existing grey and black kit and
the finish coat is causing the underlying primer to bubble up on a
small test area.

The primer is "Plasti-kote, Projekt Paint, Primer SUPER" which I
bought from B&Q. I have also bought some Simoniz Acrylic Black as a
top coat. Neither cans give specific details about their chemical
composition but they sure enough don't like each other.

I'm hoping someone can tell me of an intermediate neutral coat I can
apply to avoid having to strip the whole lot back to stage 1.


IME bubbling is usually caused by trapped solvents in the basecoat i.e.
the surface cures and stops the carrier (water or solvent) evaporating
from the lower layer. Thinner coats are usually the answer.

On Sat, 13 Jun 2009 14:37:13 GMT, Stuart Noble
wrote:

Geoff Mills wrote:
I know paint technology is a complex science but I usually get away
with it. However, I've been tarting up a pair of old Wharfdale
speakers with spray paint to match the existing grey and black kit and
the finish coat is causing the underlying primer to bubble up on a
small test area.

The primer is "Plasti-kote, Projekt Paint, Primer SUPER" which I
bought from B&Q. I have also bought some Simoniz Acrylic Black as a
top coat. Neither cans give specific details about their chemical
composition but they sure enough don't like each other.

I'm hoping someone can tell me of an intermediate neutral coat I can
apply to avoid having to strip the whole lot back to stage 1.


IME bubbling is usually caused by trapped solvents in the basecoat i.e.
the surface cures and stops the carrier (water or solvent) evaporating
from the lower layer. Thinner coats are usually the answer.

Thanks, I'll observe the thinner coat principle in future.

This job, being at the stage it is, would leaving the speakers in a
warm airing cupboard for a few days drive off enough of the primer
solvent to allow the finish coats to then go on without the bad
reaction?
--
Kind regards,
Geoff Mills

"Geoff Mills" wrote in message
...
I know paint technology is a complex science but I usually get away
with it. However, I've been tarting up a pair of old Wharfdale
speakers with spray paint to match the existing grey and black kit and
the finish coat is causing the underlying primer to bubble up on a
small test area.

The primer is "Plasti-kote, Projekt Paint, Primer SUPER" which I
bought from B&Q. I have also bought some Simoniz Acrylic Black as a
top coat. Neither cans give specific details about their chemical
composition but they sure enough don't like each other.

I'm hoping someone can tell me of an intermediate neutral coat I can
apply to avoid having to strip the whole lot back to stage 1.


How disappointing. I thought this was going to be a question about
paint affecting the sound quality. Like what kind varnish to use on my
Stradivarius?
--
Graham.

%Profound_observation%

On Sat, 13 Jun 2009 17:25:54 +0100, "Graham." wrote:



"Geoff Mills" wrote in message
.. .
I know paint technology is a complex science but I usually get away
with it. However, I've been tarting up a pair of old Wharfdale
speakers with spray paint to match the existing grey and black kit and
the finish coat is causing the underlying primer to bubble up on a
small test area.

The primer is "Plasti-kote, Projekt Paint, Primer SUPER" which I
bought from B&Q. I have also bought some Simoniz Acrylic Black as a
top coat. Neither cans give specific details about their chemical
composition but they sure enough don't like each other.

I'm hoping someone can tell me of an intermediate neutral coat I can
apply to avoid having to strip the whole lot back to stage 1.


How disappointing.

Despite my inadequacies, I rarely fail to disappoint.

I thought this was going to be a question about
paint affecting the sound quality.

Well, it most certainly does. Since this paint job started the
speakers have ben unusually silent.

Like what kind varnish to use on my
Stradivarius?

Get you!

--
Kind regards,
Geoff Mills

Geoff Mills wrote:
On Sat, 13 Jun 2009 14:37:13 GMT, Stuart Noble
wrote:

Geoff Mills wrote:
I know paint technology is a complex science but I usually get away
with it. However, I've been tarting up a pair of old Wharfdale
speakers with spray paint to match the existing grey and black kit and
the finish coat is causing the underlying primer to bubble up on a
small test area.

The primer is "Plasti-kote, Projekt Paint, Primer SUPER" which I
bought from B&Q. I have also bought some Simoniz Acrylic Black as a
top coat. Neither cans give specific details about their chemical
composition but they sure enough don't like each other.

I'm hoping someone can tell me of an intermediate neutral coat I can
apply to avoid having to strip the whole lot back to stage 1.

IME bubbling is usually caused by trapped solvents in the basecoat i.e.
the surface cures and stops the carrier (water or solvent) evaporating
from the lower layer. Thinner coats are usually the answer.

Thanks, I'll observe the thinner coat principle in future.

It's usually faster in the long run too, a thin coat drying in less than
half the time of a thick one IYSWIM

This job, being at the stage it is, would leaving the speakers in a
warm airing cupboard for a few days drive off enough of the primer
solvent to allow the finish coats to then go on without the bad
reaction?

IME no. You really need to get back to the point where the basecoat
solvent can evaporate normally, which may not be all the way back to the
original, but probably close to it. You can usually tell when it's ok by
sanding a patch with a fine paper. If the coating has cured, it should
sand to a powder with no gunk sticking to the paper.
I could be wildly wrong about all this of course, but surface coatings
rarely react with each other unless the topcoat contains a volatile
solvent (e.g. Hammerite)

In message
Geoff Mills wrote:

I know paint technology is a complex science but I usually get
away with it. However, I've been tarting up a pair of old
Wharfdale speakers with spray paint to match the existing grey
and black kit and the finish coat is causing the underlying
primer to bubble up on a small test area.

The primer is "Plasti-kote, Projekt Paint, Primer SUPER" which I
bought from B&Q. I have also bought some Simoniz Acrylic Black as
a top coat. Neither cans give specific details about their
chemical composition but they sure enough don't like each other.

I'm hoping someone can tell me of an intermediate neutral coat I
can apply to avoid having to strip the whole lot back to stage 1.

--
Kind regards,
Geoff Mills

Sometimes just using a different *solvent* can cause a reaction
problem when using different paints, even using the same solvent
at a later date can cause a reaction problem, especially with
cellulose and acrylic spray based paints.

I'm not referring to trapped solvent bubbles here, they are a
different problem altogether.

As previously suggested, leave the primer to dry sufficiently
before attempting to apply a top coat and when you do, apply a dry
coat first which will help protect the surface from over wetting,
which is the main cause of solvent reaction as the solvent
penetrates the surface underneath.

Stephen.



--
http://www.stephen.hull.btinternet.co.uk
Coach painting tips and techniques + Land Rover colour codes
Using a British RISC Operating System 100% immune to any Windows virus
"Whatever is rightly done, however humble, is noble". Henry Royce

On Sat, 13 Jun 2009 17:13:52 GMT, Stuart Noble
wrote:

snip
This job, being at the stage it is, would leaving the speakers in a
warm airing cupboard for a few days drive off enough of the primer
solvent to allow the finish coats to then go on without the bad
reaction?

IME no. You really need to get back to the point where the basecoat
solvent can evaporate normally, which may not be all the way back to the
original, but probably close to it. You can usually tell when it's ok by
sanding a patch with a fine paper. If the coating has cured, it should
sand to a powder with no gunk sticking to the paper.

There's certainly no powdering effect from sanding ATM. The surface
has a slight tackiness to the touch.

I could be wildly wrong about all this of course, but surface coatings
rarely react with each other unless the topcoat contains a volatile
solvent (e.g. Hammerite)

I think you're writing from experience and that you're probably right.
There are some variables involved though and if anyone here suggests
that further drying of the existing coats might prove beneficial, I'll
try it in preference to back-tracking.

--
Kind regards,
Geoff Mills

On Sat, 13 Jun 2009 19:09:15 +0100, wrote:

snip
Sometimes just using a different *solvent* can cause a reaction
problem when using different paints, even using the same solvent
at a later date can cause a reaction problem, especially with
cellulose and acrylic spray based paints.

My first (uneducated) impression was that the problem was caused by
using a paint containing a different solvent.

I'm not referring to trapped solvent bubbles here, they are a
different problem altogether.

The effect was more like a sort of granular eruption than bubbles,
though if magnified, it might prove to be very small bubbles.

As previously suggested, leave the primer to dry sufficiently
before attempting to apply a top coat and when you do, apply a dry
coat first which will help protect the surface from over wetting,
which is the main cause of solvent reaction as the solvent
penetrates the surface underneath.

Stephen.

Thanks for the encouragement to move forward instead of back.
That's what I'll do.
--
Kind regards,
Geoff Mills

Geoff Mills wrote:
On Sat, 13 Jun 2009 17:13:52 GMT, Stuart Noble
wrote:

snip
This job, being at the stage it is, would leaving the speakers in a
warm airing cupboard for a few days drive off enough of the primer
solvent to allow the finish coats to then go on without the bad
reaction?
IME no. You really need to get back to the point where the basecoat
solvent can evaporate normally, which may not be all the way back to the
original, but probably close to it. You can usually tell when it's ok by
sanding a patch with a fine paper. If the coating has cured, it should
sand to a powder with no gunk sticking to the paper.

There's certainly no powdering effect from sanding ATM. The surface
has a slight tackiness to the touch.

I'd say the tackiness is a dead giveaway. You could try a severe rubbing
down with coarse wire wool. This tends to pick up just the gunk but
leaves a relatively smooth surface, which should air dry quickly.


I could be wildly wrong about all this of course, but surface coatings
rarely react with each other unless the topcoat contains a volatile
solvent (e.g. Hammerite)

I think you're writing from experience and that you're probably right.
There are some variables involved though and if anyone here suggests
that further drying of the existing coats might prove beneficial, I'll
try it in preference to back-tracking.

On Sat, 13 Jun 2009 14:40:45 +0100, Geoff Mills wrote:

I know paint technology is a complex science but I usually get away
with it. However, I've been tarting up a pair of old Wharfdale
speakers with spray paint to match the existing grey and black kit and
the finish coat is causing the underlying primer to bubble up on a
small test area.

The primer is "Plasti-kote, Projekt Paint, Primer SUPER" which I
bought from B&Q. I have also bought some Simoniz Acrylic Black as a
top coat. Neither cans give specific details about their chemical
composition but they sure enough don't like each other.

I'm hoping someone can tell me of an intermediate neutral coat I can
apply to avoid having to strip the whole lot back to stage 1.

There are definite compatibility problems between cellulose and some
acrylics, so check what that primer contains. You should still be able to
get away with it if you allow plenty of time for the primer to thoroughly
dry before finish coating - ie: days rather than hours.

SteveW

On Sun, 14 Jun 2009 13:49:37 +0100, Steve Walker
wrote:

On Sat, 13 Jun 2009 14:40:45 +0100, Geoff Mills wrote:

I know paint technology is a complex science but I usually get away
with it. However, I've been tarting up a pair of old Wharfdale
speakers with spray paint to match the existing grey and black kit and
the finish coat is causing the underlying primer to bubble up on a
small test area.

The primer is "Plasti-kote, Projekt Paint, Primer SUPER" which I
bought from B&Q. I have also bought some Simoniz Acrylic Black as a
top coat. Neither cans give specific details about their chemical
composition but they sure enough don't like each other.

I'm hoping someone can tell me of an intermediate neutral coat I can
apply to avoid having to strip the whole lot back to stage 1.

There are definite compatibility problems between cellulose and some
acrylics, so check what that primer contains. You should still be able to
get away with it if you allow plenty of time for the primer to thoroughly
dry before finish coating - ie: days rather than hours.

SteveW

You were exactly right Steve, A weekend in the airing cupboard made it
possible to spray on a couple of top coats with no bad reaction. The 1
hour drying time written on the can must 've been a minimum.
--
Kind regards,
Geoff Mills