Problems using regular enamel paint in microwave oven?

[Sam Goldwasser]

Has anyone seen problems using common hardware store gloss enamel to
touch up a microwave oven interior?

Someone emailed me all in a huff that they followed this advise and it now
smells "funky" and smokes. They said the paint color was white and they
waited 24 hours before use. This was apparently under the turntable.

The smell could make sense if there was some residual solvent present and
should go away after awhile, but the "smokes" part is strange unless they
didn't bother to clean and sand beforehand and there was trapped debris.

Any comments appreciated.

--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
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| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

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[Ron(UK)]

Has anyone seen problems using common hardware store gloss enamel to
touch up a microwave oven interior?

Someone emailed me all in a huff that they followed this advise and it now
smells "funky" and smokes. They said the paint color was white and they
waited 24 hours before use. This was apparently under the turntable.

The smell could make sense if there was some residual solvent present and
should go away after awhile, but the "smokes" part is strange unless they
didn't bother to clean and sand beforehand and there was trapped debris.

Any comments appreciated.

We used to use[1] Humbrol model kit paint without any problems, indeed,
the 'proper stuff' came from the Humbrol factory and looked and smelled
exactly like the model enamel, only five times the price!

[1] back in the days when microwave oven repairs were financially viable


Ron(UK)

 

[hr(bob) [email protected]]

Has anyone seen problems using common hardware store gloss enamel to
touch up a microwave oven interior?

Someone emailed me all in a huff that they followed this advise and it now
smells "funky" and smokes. They said the paint color was white and they
waited 24 hours before use. This was apparently under the turntable.

The smell could make sense if there was some residual solvent present and
should go away after awhile, but the "smokes" part is strange unless they
didn't bother to clean and sand beforehand and there was trapped debris.

Any comments appreciated.

--- sam | Sci.Electronics.Repair FAQ:http://www.repairfaq.org/
Repair | Main Table of Contents:http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ:http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites:http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

Sam:

I think you are 100% correct. There should be no hot spots anywhere
on the uwave oven liner as it is a solid metal sheet except where the
uwaves come into the chamber. There is obviously a fault of some type
that is making that area of the uwave get hot or there would not be
any smoke. That may be why there was a fault in the original paint at
the location.

BTW - I think you are right on in just about everthing you recommend,
and your repair faq stuff is a great resource.

H. R.(BOb) HOfmann

 

[GregS]

Has anyone seen problems using common hardware store gloss enamel to
touch up a microwave oven interior?

Someone emailed me all in a huff that they followed this advise and it now
smells "funky" and smokes. They said the paint color was white and they
waited 24 hours before use. This was apparently under the turntable.

The smell could make sense if there was some residual solvent present and
should go away after awhile, but the "smokes" part is strange unless they
didn't bother to clean and sand beforehand and there was trapped debris.

Some black paints are electrically conductive, but even that should be no problem unless
it was across an insulator like glass. Probably just the residuals from a little heat and moisture
from normal cooking. The oven should have been baked. Did I say that right? At least
a hot air gun or hair dryer shold ahve been used to treat the paint first.

greg

 

[GregS]

Some black paints are electrically conductive, but even that should be no
problem unless
it was across an insulator like glass. Probably just the residuals from a
little heat and moisture
from normal cooking. The oven should have been baked. Did I say that right? At
least
a hot air gun or hair dryer shold ahve been used to treat the paint first.

Come to think of it, materials can be lossy at microwave frequency, so
even if it were not dc conductive, a material could heat up if were suspended
across an insulator.

My black electrically conductive seal on the old Heathkit microwave,
use to kind of melt.

greg

 

[[email protected]]

Has anyone seen problems using common hardware store gloss enamel to
touch up a microwave oven interior?

Someone emailed me all in a huff that they followed this advise and it now
smells "funky" and smokes. They said the paint color was white and they
waited 24 hours before use. This was apparently under the turntable.

The smell could make sense if there was some residual solvent present and
should go away after awhile, but the "smokes" part is strange unless they
didn't bother to clean and sand beforehand and there was trapped debris.

Any comments appreciated.

Sam:

A couple of things come to mind, both of them pretty remote:

a) the batch of paint used had Titanium Dioxide as the white pigment.
It is just possible that the paint as-applied was more absorbtive than
the OEM paint & metal combination and so that area turned into a 'hot-
spot'. If they did an area say the size of a business card or more,
that would be the second thing that came to mind and that based only
on very careful prep... see b) below.
b) conversely and more likely, the prep-work took the microwave-
reflective primer off and exposed the steel. BAD MOVE as without that
reflective coating the metal will get very hot no matter what sort of
finish coating may be on top.

Just my random thoughts.

Peter Wieck
Wyncote, PA

 

[[email protected]]

b) conversely and more likely, the prep-work took the microwave-
reflective primer off and exposed the steel. BAD MOVE as without that
reflective coating the metal will get very hot no matter what sort of
finish coating may be on top.

Just my random thoughts.

Peter Wieck
Wyncote, PA

Does anyone agree with this?

 

[[email protected]]

Does anyone agree with this?

To understand what the walls of the oven are made of or what material
one could use to partially keep food from cooking, you have to have
some knowledge of 'dielectric constant' and 'loss tangent'. The
materials used for protectors can be plastics, ceramics.... all
depends on the dielectric constant and the RF properties at 2.45 GHz.
The walls are usually a light sheet metal (or plastic with a layer of
metal foil) with a dissipative coating.

from: Ronna Erickson
Radio Astronomy, Univ. of Mass. - Amherst

Remove that dissipative coating and Bob's your Uncle...

In any quality oven, that coating is fired enamel and pretty tough. In
the cheaper versions, it is a powder-coating that is fragile at best
if abrasives are used to clean. On some others, it is back-coated onto
a tough plastic... That is the hardest to damage.

Peter Wieck
Wyncote, PA

 

[larry moe 'n curly]

A couple of things come to mind, both of them pretty remote:

a) the batch of paint used had Titanium Dioxide as the white pigment.
It is just possible that the paint as-applied was more absorbtive than
the OEM paint & metal combination and so that area turned into a 'hot-
spot'. If they did an area say the size of a business card or more,
that would be the second thing that came to mind and that based only
on very careful prep... see b) below.

b) conversely and more likely, the prep-work took the microwave-
reflective primer off and exposed the steel. BAD MOVE as without that
reflective coating the metal will get very hot no matter what sort of
finish coating may be on top.

Does that apply only if there's a coating on top of the metal?
Because we have a microwave oven with a stainless steel interior

 

[Sam Goldwasser]

Does that apply only if there's a coating on top of the metal?
Because we have a microwave oven with a stainless steel interior

So how is stainless steel different than steel, microwave-wise? To reflect
microwaves implies a conductive material. The conductivity may be different,
but not dramatically.

--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

 

[[email protected]]

So how is stainless steel different than steel, microwave-wise? To reflect
microwaves implies a conductive material. The conductivity may be different,
but not dramatically.

--- sam | Sci.Electronics.Repair FAQ:http://www.repairfaq.org/
Repair | Main Table of Contents:http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ:http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites:http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.- Hide quoted text -

- Show quoted text -

There are several patterns to how the magnetron works, and several
methods to spread the pattern over the food. "Better" ovens use a
combination of reflection and absorbtion to make the food cook evenly,
*in addition* to either a turntable or even the figure-8 pattern
turntables on some higher-end ovens. In these cases, the Turntable
platter and mechanism serves as the absorber, the vertical surfaces
will be the refectors.

In the cheaper fixed-position ovens where one is required to rotate
items or turn them over, the niceties of such designs are ignored and
the magnetron pretty much blasts in whatever pattern it is masked to
do. Scatter is to be absorbed by the surfaces of the oven.

There is a great deal of thought and design that is hidden in these
beasts. It is absolutely possible to put out an oven at US$39 that
will both cool and still make a profit for the retailer even after it
is shipped from China. It is also possible to spend $600 for an oven
that will not only cook but have all of these design niceties included
and still make a profit for the dealer even after it has been shipped
from China.

Point being that everything inside that oven, right down to the paint,
has been chosen for the purpose. And if they are stainelss steel
lined, that steel has also been 'designed' for the purpose. Can't go
by smell on the paint, can't go by looks on the steel.

Peter Wieck
Wyncote, PA

 

[[email protected]]

There are several patterns to how the magnetron works, and several
methods to spread the pattern over the food. "Better" ovens use a
combination of reflection and absorbtion to make the food cook evenly,
*in addition* to either a turntable or even the figure-8 pattern
turntables on some higher-end ovens. In these cases, the Turntable
platter and mechanism serves as the absorber, the vertical surfaces
will be the refectors.

In the cheaper fixed-position ovens where one is required to rotate
items or turn them over, the niceties of such designs are ignored and
the magnetron pretty much blasts in whatever pattern it is masked to
do. Scatter is to be absorbed by the surfaces of the oven.

There is a great deal of thought and design that is hidden in these
beasts. It is absolutely possible to put out an oven at US$39 that
will both cool and still make a profit for the retailer even after it
is shipped from China. It is also possible to spend $600 for an oven
that will not only cook but have all of these design niceties included
and still make a profit for the dealer even after it has been shipped
from China.

Point being that everything inside that oven, right down to the paint,
has been chosen for the purpose. And if they are stainelss steel
lined, that steel has also been 'designed' for the purpose. Can't go
by smell on the paint, can't go by looks on the steel.

Peter Wieck
Wyncote, PA

Maybe you dont repair microwaves.


NT

 

[[email protected]]

Maybe you dont repair microwaves.

NT- Hide quoted text -

- Show quoted text -

Put as simply as possible, I would not, no. And this from someone
whose hobby (amongst others) is restoring vintage radios and audio
equipment from the 20s - 70s.

Peter Wieck
Wyncote, PA