paint and "fog coat"

TJ in KY · Aug 14, 2016

I did not want to hijack the "paint" post below but what is a "fog coat". I have not heard that term before. Getting ready to do some sheetmetal and I was just wondering, is it just a light mist??

duey · Aug 14, 2016

YUP, you've got it....

Tall T · Aug 14, 2016

(quoted from post at 17:52:12 08/14/16) I did not want to hijack the "paint" post below but what is a "fog coat". I have not heard that term before. Getting ready to do some sheetmetal and I was just wondering, is it just a light mist??

Careful you don't make the same mistake I did.
I sprayed some Acrylic Lacquer but thinking to minimize the chance of runs or drools I first applied a mist or fog coat, and another and another. Big mistake, fog coat FIRST does not fly with Lacquer and so i wound up with a matt finish that feels like sandpaper.

So, says I to myself, that's what they meant when they said that with lacquer specifically apply a WET coat first, the total opposite of a FOG coat.

I had read about the WET coat before painting but had no clue what "wet coat" meant and how critical it was so I totally blew it. So . . . I painted two other inside panels in my cornbinder cab with the same paint but applied a wet coat first. Bingo!
Shiny and smooth.

Den N Ms · Aug 14, 2016

A fog coat will get you pop corn or orange peal finish.You want wet coats,just wet enough that it dosen't run and a flash time between coats.

Caryc · Aug 14, 2016

Way back when I was in auto shop in school, the teacher called it a tack coat. He demonstrated it spraying lightly the areas where paint was most likely to run on you.

That tack coat gave the real coat something to stick to.

Tall T · Aug 15, 2016

(quoted from post at 21:08:40 08/14/16) A fog coat will get you pop corn or orange peal finish.You want wet coats,just wet enough that it dosen't run and a flash time between coats.

Den,

Flash time between coats is critical for sure even for certain primers!

I phoned the Eastwood Urethane Car Specialists who recommend Urethane primer or epoxy primer. I told him I had used some self-etching primer and he said that would be OK but to be sure to allow 10 to 15 minutes for the self-etch primer to flash then paint [b:4f154b7341]immediately![/b:4f154b7341]

OTHERWISE
If self-etching primmer is left longer than the flash time the primed surface must then be scuffed up with the red scuff pads before painting.

It gets really tricky when having a whole slew of tractor parts hanging up and being painted, trying to keeping track of the flash time so as to properly apply a second coat of paint.

Ultradog MN · Aug 15, 2016

I guess like every thing else terminology
may be regional - maybe generational.
To me a fog coat is a light, medium coat
that is merely to start covering the
surface. Too heavy a first coat and it
will start to run. A second coat will
adhere to the fog coat which has already
started to set up - more quickly with a
hardener - and covers the surface mote
fully. The flash coat is what gives you
the shine.
In my experience, the quickest way to get
orange peel is too high of air pressure
and/or not enough reducer. Not so much the
application of the paint.

TheOldHokie · Aug 15, 2016

(quoted from post at 07:40:31 08/15/16) I guess like every thing else terminology
may be regional - maybe generational.
To me a fog coat is a light, medium coat
that is merely to start covering the
surface. Too heavy a first coat and it
will start to run. A second coat will
adhere to the fog coat which has already
started to set up - more quickly with a
hardener - and covers the surface mote
fully. The flash coat is what gives you
the shine.
In my experience, the quickest way to get
orange peel is too high of air pressure
and/or not enough reducer. Not so much the
application of the paint.

When I don't know the answer I often ask Google. I quickly found many technical descriptions and discussions of this practice. In the current auto paint vernacular a fog coat/drop coat is used when spraying metallic colors. After the wet coats have been applied a final "fog coat" of the color is sprayed to produce an even orientation/pattern of the flakes. This reduces the chance of striping or mottling and improves panel match. Fog coats are not needed or recommended when spraying non-metallic colors.

TOH

Tall T · Aug 15, 2016

UD,

You wrote:

"The flash coat is what gives you
the shine."

Regardless of region or generation I think that "flash coat" is a total misnomer.

Flash TIME is what [b:048c915dec]flash[/b:048c915dec] is all about, allowing the specified time for solvents in any given paint to evaporate before any followup application of paint.

So in that case every coat would be a flash coat but that would make the term "flash coat" of no useful meaning.

Flash time is the time between coats.
Here's a video explaining Flash Time and Window Time.
FlashTime

T

Tall T · Aug 15, 2016

Correction:
Flash Time isn't as I simplistically put it, "the time between coats". it is the minimum time that must be allowed before the next coat.

Beyond that time the "Window Time" comes into play.

TJ in KY · Aug 15, 2016

Thanks guys. I always find all responses helpful. Having some minor surgery on Wednesday and then hope to get started on
sheetmetal.

paint and "fog coat"

TJ in KY

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duey

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Tall T

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Den N Ms

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Caryc

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Tall T

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Ultradog MN

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TheOldHokie

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Tall T

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Tall T

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TJ in KY

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