Messuring clearcoat with single paint gauge

[Charlieboy1]

Hi people
just wondering how people can measure and judge how much clear coat is on the car when using a normal paint depth gauge that has a whole reading and not like the expensive ones that read each layer.
I understand people start doing test spots starting with least aggressive combos etc but doesn’t explain
rough clear coat guide if that makes any sense
people have different ways of doing this but just wanted to know peoples views on this

Thank you
Charlie

[dennis hiip]

I wondered the same thing and reasoned that a gauge is useless unless you spend the big bucks.

[waelwell]

All an inexpensive paint gauge can give you is a rough idea of what's going on with a base coat/clear coat paint job. Most new cars seems to measure out around 5 mils of total paint thickness. Mike Phillips tells us that, new, we're looking at 2 mils of clear coat.

Clearcoats are thin

So if you're looking at a fairly new car that hasn't been resprayed then you can do a little math to give yourself a rough idea of what is going on. Outside of those parameters I don't rely on the gauge to tell me much.

Bill

[DMiglio]

The only way I’ve heard/read to get a rough estimate is to measure a panel and then measure a door jamb. Take those measurements and subtract the door jamb from the panel measurement.

The theory behind this is that (according to what I’ve read), the jambs won’t be clear coated whereas the exterior panels will be. All in an effort for car companies/manufacturers to save on build cost.

[waelwell]

So you're saying that if I took a towel and some polish to a door jamb, the paint color would transfer to the towel (no clear coat)? I've never seen that happen.

Bill

[Rsurfer]

The only way I’ve heard/read to get a rough estimate is to measure a panel and then measure a door jamb. Take those measurements and subtract the door jamb from the panel measurement.

The theory behind this is that (according to what I’ve read), the jambs won’t be clear coated whereas the exterior panels will be. All in an effort for car companies/manufacturers to save on build cost.

You were correct up to where you stated that there was no clear coat on the door jambs. The clear coat on the door jambs are not as thick as on the body panels. This should give you a rough estimate of the amount of clear you have to work with. IMO you should not compound a car with less than 90 microns.

[Calendyr]

The only way I’ve heard/read to get a rough estimate is to measure a panel and then measure a door jamb. Take those measurements and subtract the door jamb from the panel measurement.

The theory behind this is that (according to what I’ve read), the jambs won’t be clear coated whereas the exterior panels will be. All in an effort for car companies/manufacturers to save on build cost.

That is correct most of the time. There are exceptions. ie, I did a BMW X5 yesterday and the paint mesurements on the hood were in between 150 to 200 microns. I measured the door jamb and was getting 160-180 readings. So in a case like that, the door jamb mesurement is useless. Most of the time, the door jamb will give you reading much lower than the panel, in that case, you can be pretty sure that the diffence is actual clearcoat surplus.

When the readings are equal between the jamb and panel, I consider that about half that paint thickness is clearcoat and the other half is primer+basecoat. So on a reading of 150, I would consider the clear to be 75 microns thick. I really try never to remove more than 10 microns of clear if possible. And if the paint is really thin (say 100 microns or less) I would advise against any wet sanding or heavy compounding. You may not go through the clear but you might leave so little behind that it will fail prematurelly.

[DMiglio]

Awesome info! Thanks for responding guys, not only did I get a clearer understanding of what I had typed about the panel/door jambs, but hopefully too helped the OP and any others who read this.

Waelwell, reading your post made me realize just how wrong my post was... door jamb paint transfer never happened to me either.

[Charlieboy1]

That is correct most of the time. There are exceptions. ie, I did a BMW X5 yesterday and the paint mesurements on the hood were in between 150 to 200 microns. I measured the door jamb and was getting 160-180 readings. So in a case like that, the door jamb mesurement is useless. Most of the time, the door jamb will give you reading much lower than the panel, in that case, you can be pretty sure that the diffence is actual clearcoat surplus.

When the readings are equal between the jamb and panel, I consider that about half that paint thickness is clearcoat and the other half is primer+basecoat. So on a reading of 150, I would consider the clear to be 75 microns thick. I really try never to remove more than 10 microns of clear if possible. And if the paint is really thin (say 100 microns or less) I would advise against any wet sanding or heavy compounding. You may not go through the clear but you might leave so little behind that it will fail prematurelly.

Thanks for the feedback yeah I always thought anything over say a little more than 100 was safe
just say you have panels that are resprayed how can you do that meathod I suppose it’s tricky right?

[Charlieboy1]

That is correct most of the time. There are exceptions. ie, I did a BMW X5 yesterday and the paint mesurements on the hood were in between 150 to 200 microns. I measured the door jamb and was getting 160-180 readings. So in a case like that, the door jamb mesurement is useless. Most of the time, the door jamb will give you reading much lower than the panel, in that case, you can be pretty sure that the diffence is actual clearcoat surplus.

When the readings are equal between the jamb and panel, I consider that about half that paint thickness is clearcoat and the other half is primer+basecoat. So on a reading of 150, I would consider the clear to be 75 microns thick. I really try never to remove more than 10 microns of clear if possible. And if the paint is really thin (say 100 microns or less) I would advise against any wet sanding or heavy compounding. You may not go through the clear but you might leave so little behind that it will fail prematurelly.

Thanks for the feedback yeah I always thought anything over say a little more than 100 was safe
just say you have panels that are resprayed how can you do that meathod I suppose it’s tricky right?