Problems using regular enamel paint in microwave oven?
Sam Goldwasser
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.
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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) hofmann@att.net
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
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
pf...@aol.com
> 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
meow...@care2.com
> 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?
pf...@aol.com
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
pf...@aol.com wrote:
> 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
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.
pf...@aol.com
> "larry moe 'n curly" <larrymoencu...@my-deja.com> writes:
>
> - 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
Sam Goldwasser
Here is a reply from John Gallawa of Microtech at
http://www.gallawa.com/microtech/, generally regarded as the most
comprehensive site for microwave ovens on the Web.
First my question (similar but not word-for-word what I posted here)
and then John's reply:
>> Someone emailed me in a huff about having used ordinary paint to touch
>> up a microwave and now everything "smells funky" and it "smokes". This
>> was done under where the turntable wheels move.
>> Have you ever heard of problems of this type? They say that it was
>> white gloss enamel, that they waited 24 hours for it to dry, and that
>> surfaces were cleaned thoroughly.
>> I've been trying to get them to do some tests to determine if it is a
>> continuing problem or just residual solvent odor that will go away.
>> I had them remove the turntable and just put a cup of water in to act
>> as a load. They then said there was no smoke but the water smelled so
>> bad they couldn't get near it.
>> Any info would be appreciated.
>> Thanks!
>> --- sam
> From: John (via email):
>
> First, though, it is probably not the paint. If they used standard
> enamel, that should be fine. We used to use off-white enamel to repaint
> cavities.
>
> If the reason they cleaned and repainted the cavity surfaces was because
> of discoloring due to arcing, then possibly there were some tiny (the
> size of a needle point is all it takes) traces of carbon residue that
> were not completely eliminated and were subsequently painted over. Or
> perhaps the wheels of the roller ring/turntable assembly have developed
> microscopic carbon tracks that are producing small amounts of arcing.
>
> Of course, there is the possibility of another problem that is just
> coincidental to the paint job. For example, there could be infinitesimal
> amounts of arcing from the waveguide cover to an adjacent metal surface,
> so small that it is goes noticed.
>
> For removing residual odor, we have always had good success by
> placing used coffee grounds in the cooking cavity overnight for several
> nights. The grounds do a good job of absorbing lingering odors.
>
> The only problem we ever had with re-painting cavities was the fact that
> we weren't a paint shop. As long as the surfaces were properly prepared
> (and that was always the crucial part), though, and the paint was
> appropriately applied, the outcome was usually acceptable. While cavity
> paint was available from some manufacturers, in many cases, we would
> simply purchase a can of off-white enamel from the local hardware store,
> and this served the purpose.
In fact, I have now been able to determine from testing done by the
person who originally was complaining that it is probably just residual
odor at this point. I had them run the oven with just a water load to
see if the area of the new paint heated up or behaved strangely. It
did not. They'll have to try the coffee grounds I guess. :)
Thanks to all who responded.
meow...@care2.com
Maybe you dont repair microwaves.
NT
pf...@aol.com
>
> - 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