Paint Surface Temperature Discussion

zenhog · 08-24-03, 01:25

I'm sending up a pic of the temp I took of my car sitting outside today under a slightly-overcast sky.

150+ degrees!

Yesterday when I bought the Radio Shack gauge there was direct sunlight, no clouds, and spots were 170+ degrees!

I don't know where this idea came from that if, while polishing, you'll burn your paint if you get the surface temp to 150 or higher, but unless we're all running around with burned paint jobs, I think that temp statistic may need to be re-visited.

Or maybe someone can explain to me why 150 under the sun is different than 150 under a foam pad?

theveed · 08-25-03, 03:51

friction induced heat is different from air-borne heat... that's my theory...

Jimmy Buffit · 08-25-03, 04:26

Theveed is in the right direction. Friction of buffing literally moves molecules on the surface of the finish. That is what leaves buffer swirls.

The static temp of your paint in the sun is an example of wht sealants (with a >300 degree melting point) are superior to waxes (with a 165 degree melting point).

Did you take the interior temp? It is pure hell in there!

Jim

zenhog · 08-25-03, 04:57

No, I didn't take the interior temp, but that brings up a good thought. No wonder why dogs don't last very long in a car in the heat!

But.. that's not a problem with me.. (I have a convertible) lol

It's going to hit 100 here today, I'll try to get outside and catch a temp reading during the heat of the day. I bet I get something around 170 or more!

C

BryanPendleton · 08-25-03, 03:36

Quote:

Originally posted by jimamary
Theveed is in the right direction. Friction of buffing literally moves molecules on the surface of the finish. That is what leaves buffer swirls.

I don't buy it. . .
1) High speed rotary buffer can induce temps in excess of 150F easily. I would not be surprised in temps of 400F+ were reached in local hots spots.

ie. I do alot of aluminum polishing and buffing with high speed buffers and polishing compounds. This often yields aluminum at temps that are in excess of the melting point of many plastic, in other words, I can melt plastic on a aluminum surface that I have buffed.

2) You are not going to move the "molecules" or clearcoat if its still in solid form. You must heat it to the point where it begins to flow which will be at or near melting point of the clearcoat.

StickKing1 · 08-25-03, 04:36

Sorry, a bit off topic, but.....how much was the temp reader?

zenhog · 08-25-03, 04:50

Brian (StickKing1) get over to Radio Shack now, they're on sale for $29. Normally $49. (8/23/03)

StickKing1 · 08-25-03, 05:06

Whoo...cool stuff. I'll be there tomorrow!

Mike Phillips · 08-25-03, 05:10

Quote:

Originally posted by BryanPendleton

2) You are not going to move the "molecules" or clearcoat if its still in solid form. You must heat it to the point where it begins to flow which will be at or near melting point of the clearcoat.

Actually, you don't need high temperature to move molecules.

Wet-sanding for example moves molecules without heat.

(assuming your wet sanding water is out of the cold side of the sink or out of the garden hose).

This would have to do with the abrading characteristics of whatever product your using.

Another example would be how old timers would hand rub lacquer finishes using either a traditional compound or a diminishing abrasive like MGH-4 Hand Cleaner, (pre-1940's).

Yet another example would be the Porter Cable Dual Action Polisher. One of the reasons its safe is because it Jiggles instead of rotates via direct drive. While yes, it can generate heat, it’s abrading power comes from the application material, your choice of chemical, pressure, time, heat and physical action. It’s a combination of all of these that are doing the abrading, but they are not necessarily dependent upon heat in order to remove/flatten/polish/smooth-out paint.

FWIW

YoSteve · 08-25-03, 10:46

the kenetic energy enduced by a polisher is used towards abrading the surface

if it wasn't then it would heat up (takes a lot of kinetic energy to make heat)

going the other way around is different (and harder to theorize), it takes a lot of heat energy with out kinetic to induce abrasion the other direction.

the temperature of the pigmented paint is going to be different form that of the clearcoat paint, use a thermocouple instead and try to get a surface reading.

just theories, i guess ???

BryanPendleton · 08-26-03, 07:10

Quote:

Originally posted by Mike Phillips
Actually, you don't need high temperature to move molecules.

Wet-sanding for example moves molecules without heat.

(assuming your wet sanding water is out of the cold side of the sink or out of the garden hose).

This would have to do with the abrading characteristics of whatever product your using.

Another example would be how old timers would hand rub lacquer finishes using either a traditional compound or a diminishing abrasive like MGH-4 Hand Cleaner, (pre-1940's).

Yet another example would be the Porter Cable Dual Action Polisher. One of the reasons its safe is because it Jiggles instead of rotates via direct drive. While yes, it can generate heat, it’s abrading power comes from the application material, your choice of chemical, pressure, time, heat and physical action. It’s a combination of all of these that are doing the abrading, but they are not necessarily dependent upon heat in order to remove/flatten/polish/smooth-out paint.

FWIW

Yes, I am aware that you can move clearcoat and paint molecules by abrasding and sanding, etc. But Zenhog's reference was towards "burned paint jobs", which can occur using a high speed rotary buffer/polisher. His confusion, was that he was told paint "burns" at 150F, but he is measuring temps in excess of 150F just sitting outside. My argument is that paint temperature reach temps well in excess of probably 300F, when burning the paint with the use of a rotary buffer. The "burning" that occurs with rotary buffer use, from my understanding, is:

a large portion of the kinetic energy from the buffer in being converted to heat energy at the interface between the paint and buffer. When the heat in that localized area cannot be transfered away fast enough the paint becomes heat saturated, and temps begin to elevate to the point when the clear or paint actually begins to flow.

That is my understanding of "burning" paint with a rotary, and it is my understanding that this occurs because of the excessive temperatures which the paint reaches. Sure the chemical, pressure, time and buffer action all come into play. The combination of those are what actually determines how much heat is generated through the conversion of kinetic energy to heat energy

I am open for discussion.

Mike Phillips · 08-26-03, 08:05

Your description of when paint begins to burn sounds right on to me.

Burnt paint.

Been there... done that.... don't want to do it again.

Mike