Number of coats and mil thickness question?

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PostPosted: Thu Mar 08, 2018 5:36 pm
Hi Guys,
I've been following along with all the post people post and often I here "How many coats of clear", and someone at some point mentions mil thickness. So it makes me think that one guys coat/mil thickness may not be equal to the next guys because of the variables like gun setup, gun travel speed, materiel being sprayed, etc....

So my question is: To determine how many coats of clear I should apply, should I simply read the tech sheet to see the recommended total mil thickness and then spray some test coats and measure the mil thickness with a gauge to see how many coats it will take me to get the right amount with my technique and setup? Is that a logical way do determine the number of coats or am I over thinking this?

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PostPosted: Thu Mar 08, 2018 7:46 pm
no you are not over thinking. i would get a wet mil thickness gauge or check mils on panel before you spay and check it when done. im stepping away from computer i can go into depth tomorrow
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PostPosted: Thu Mar 08, 2018 10:45 pm
Yep, what he said :goodpost: My first professional finishing classes back almost 40 years ago now stressed to learn spec. sheets and how to use a wet film gauge. At most of the wood trade shows I go to now and then the suppliers hand these out for free with their logos on them. Those are the simplest to get you used to "how" say for example 4 mils wet looks. And, yes, there is quite a difference in what some guys call a "coat." You are NOT overthinking this....you will learn to put down a better/more durable coating with less troubleshooting needed.
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PostPosted: Fri Mar 09, 2018 10:50 am
mil thickness is a very over looked and pretty important part of painting.

people always ask "how many coats" we all do it, even me.
when we ask that question we are over looking the "mil" the correct question is
"how many mils" and that answer depends on the product.

if you compare Feather Fill vs most 2k primer you will see a big difference in recommended mil build. HoK clear vs most production clears.

take a clear that is 50% solids and you need 2 mils dry, use your wet mil gauge and spray 4 mils wet, 50% of that will go away leaving you the recommended 2mil.

another mistake i believe both manufactures and painters practice is the whole crap about only one coating your blend panels. IMO that does not meet the required mil spec just because you go on top of clear i dont believe it adds to your mil protection because they have not cross linked together. that thin film is on top of another and are of two separate layers.

any of this make sense ?
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PostPosted: Fri Mar 09, 2018 12:30 pm
Absolutely. That's what kept bring me back to actually measuring the actual results of my setup and technique to see what it takes to get it where it needs to be for each product being used.

Also, when the tech sheet does not specify dry or wet, which does it mean.

Example:
Clear: MS-42
Hardeners: MH-43, MH-005, MH-006 or MH-008
Mixing Ratio: 2:1
Viscosity #2 Zahn (RTS): 20 - 25 seconds #2 Zahn
Weight Solids (RTS): 49.01 - 49.45%
Volume Solids (RTS): 42.03 - 42.04%
Film Build: 1.0 - 1.2 mils per full coat
Coverage: 674 sq. ft. per gallon @ 1 dry mil

I would think the Film Build: 1.0 - 1.2 mils per full coat would mean after drying.

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PostPosted: Fri Mar 09, 2018 1:57 pm
OEM paint is about 1.5 - 2.0 mils as my own rule i like a little more than that.
here is DCU2021 with about the same info so im guessing that is a dry mil
http://www.automotivepaintandequipment. ... 021pic.pdf
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