why wet sand a show car??????????

w0lfy

w0lfy

New member
Please forgive my ignorance in the wet sanding area of detailing :wall
I will try to explain as best i can what i am asking as i really want to know lol; so here goes .......

Ok, so, As I understand in the wet sanding you can 1) sand all clear,paint,base coats (leaving only metal ) to repaint a whole car or panel completely. or 2) wet sand a area which has a deep scratch for scratch removal (followed by compound/polishing & waxing to restore finish) such example may be a car keyed from front to rear quarter panels.

But ok ...... Why would a show car need wet sanding Wet Sanding for Show Car Results - DetailCity.org - Auto Detailing & Car Detailing Forum ? or am i misreading they sub-topic?
I mean, are you taking a car that's got serve swirls and scratch and restoring the finish to a show car shine or are you actually speaking of taking a show car (near to flawless paint) and wet sanding it, lol ?If the later is the case a lil explanation as to why would be greatly appreciated.

Once again, Please forgive my ignorance in the wet sanding area of detailing :wall
 
And unless you are going to repaint the whole car why the heck would you wet sand the whole thing? really?
 
When a detailer talks about wet sanding or damp sanding , it is usually for the removal of any small imperfections in the paint that buffing won't or can't remove. On a re-paint this may cover small runs or sagging , dust or dirt nubs etc.On factory paint jobs its mostly orange peel or minor scratches or defects. When doing this process you only remove a very minor amount of paint and not down to the metal. This is not a pratice that is done on most dailey drivers. This process takes a little knowledge of paint and some patience to keep from doing more damage then good. Not only must the surface be sanded correctly but then be polished and buffed out correctly .
 
Colour Sanding (Wet-sanding)

Years ago it was called colour sanding because automotive paints were single-stage (primer and a colour coat) and when the finish faded from ultra violet radiation (UVR) exposure, sanding off the oxidized paint thereby exposing the underlying paint would bring back the paint surface colour. Then, as now, most sanding was done wet so the terms colour sanding, wet sanding and as all these process involves a sanding block, block sanding all became interchangeable whether you were sanding for colour or for a level surface.

What makes a scratch visible is that it makes the paint surface two-dimensional and the light reflects from the microscopic fissures and scratches differently from the rest of the paint surface

Block wet- sanding (finishing paper and a sanding block) is considered the most efficient form of paint correction, by ensuring a consistent pressure over the entire surface contact area and using a long stroke; this is the most effective tool for paint defect removal because of its linear process you abrade the paint surface flat until the defects are removed and a perfectly ‘flat’ levelled surface is obtained by block wet-sanding the paint surface.

This provides an optimum surface light reflection / refraction (in simple terms the light reflectance from a mirror)
 
"Wetsanding for showcar results" - keyword "results". Meaning basically that wetsanding, when done right, will produce a flawless finish much like you would see on a showcar. Everyone has their own opinions and methods toward wetsanding, myself included. Its definatly not something I suggest doing unless its the last resort, or its fresh paint (and thats the bodyman's job to sand and buff what he painted).
 
Many times a restored car or repaired car will get what they call die back or shrinkage.

Shrinkage is a result of heavier sand marks under the basecoat showing up after the paint has been sanded flat. This is usually the result of not using the finest grit possible before proceeding to color coats.
Die back happens from the lower layers of clear hardening after the top.
The most common example of shrinkage is after collision repair and you start seeing "lines" in the paint.

Most cars have orange peel which masks this show cars do not.
 
Just to make sure there's no confusion...

Normally a car built to be a show car is sanded after it is painted, usually within days but it could be weeks. This is part of creating a show car.

A show car is not normally sanded years after it is built and painted to give it a show car finish, it's done during the build.

You can take a car that was built and painted but never wetsanded and then sand and buff it but usually it's done shorty after painting while there's a "window of time" where the paint will buff easier.

Whether a car is sanded and buffed is up to the owner of the car and how informed he is and what he's willing to pay for at the time the car is painted.



I posted this to MOL this morning,

Mike Phillips said:
"Sanding is the easy part, that's putting scratches into the paint, the tricky part is getting them out"


Technically we instill sanding marks, but in the context of the idea I try to get across on the topic of sanding, the word scratches fits better. Then back it up with sound information and education and everyone gets the idea.

Something I've noticed in all the years I've been teaching classes is that most the people that sign-up for the advanced class to learn how to wetsand, after they learn how to do it and what's involved, they find they don't really want to do it.


It's always easy to wetsand paint, that's putting scratches into the paint, the tricky part is removing the sanding marks
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As paint dries, hardens, fully sets-up or cross-links, it becomes less polishable, or in other words, harder to buff sanding marks out of... there's a window of time where the paint is still wet, not wet as in gooey wet, but wet as in still easily buffed and if possible, you want to sand and buff the car during this window of time.

With new sanding products as well as compounds, it is easier than ever to sand and buff a car as compared to how it was done just a few years ago...


:)
 
Well I guess that leaves out my show car Jeep from becoming show car Jeep quality! lol Actually I was wondering the same thing. Great info here. :D
 
Concours.John said:
Many times a restored car or repaired car will get what they call die back or shrinkage.

Shrinkage is a result of heavier sand marks under the basecoat showing up after the paint has been sanded flat. This is usually the result of not using the finest grit possible before proceeding to color coats.
Die back happens from the lower layers of clear hardening after the top.
The most common example of shrinkage is after collision repair and you start seeing "lines" in the paint.

Most cars have orange peel which masks this show cars do not.
Click to expand...

Great post. I have worked on several Pebble Beach winners, that several years after winning the award, no longer look like the day they were deemed flawless.

Much like an athlete, it is possible for a car to be in its prime for only a short while. Even bondo can shrink over time, which causes on top to shrink as well.

A lot of 'so called' perfect cars have a lot of body filler on them. Depending on the amount and variences in thickness, it will shrink, some degree, over time.
 
Todd Helme said:
A lot of 'so called' perfect cars have a lot of body filler on them.
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Perhaps checking a car for excessive filler would be a good thing to add to the judging at concours events; that way only the very best restorations and "original" cars that were repaired using very good metalwork techniques can pass the test.... :inspector:

What can I say? I place a lot of value on seeing jobs done right by skilled technicians.
 
CH.Detailing said:
What about Dinos? They were purposely built with a skim coat at the factory!
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My understanding is a lot of the coat built Italian cars from this vintage are very much like this.

You would not believe the amount of sanding lines and body filler shrinkage on an original paint LP-400 (Countach) that I did. It was just scary, particularly on the lower fenders. Even modern, catalyzed body fillers still shrink to some degree.

I remember reading a post on a Porsche Restorer who was restoring an aluminum bodied Ferrari 308 and the amount of filler on the body was crazy. IIRC, he sanded and scrapped most of it off, swept it into a pile, and weighted it, and it was something like 15 lbs!
 
Todd Helme said:
My understanding is a lot of the coat built Italian cars from this vintage are very much like this.

You would not believe the amount of sanding lines and body filler shrinkage on an original paint LP-400 (Countach) that I did. It was just scary, particularly on the lower fenders. Even modern, catalyzed body fillers still shrink to some degree.

I remember reading a post on a Porsche Restorer who was restoring an aluminum bodied Ferrari 308 and the amount of filler on the body was crazy. IIRC, he sanded and scrapped most of it off, swept it into a pile, and weighted it, and it was something like 15 lbs!
Click to expand...

This is true. Here is factory filler on gelcoat. The body is fiberglass built by Ghia in 65. It was obviously a mold imperfection which means everyone had it in the same spot on the hood.


a6936043-e1dc-db26.jpg


On another note here is an overlay repair done in the past. The body was leveled with filler. This has to go!
a6936043-e500-5036.jpg

a6936043-e548-96d8.jpg
 
Maybe someone in the know could answer this. When cars are painted at the factory, is there a group of guys who sand and buff every car that rolls off the line, or are the painting robots so dialed in that the paint simply comes out perfect every time?
 
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