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Old 10-28-2009, 10:12 AM   #1
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Wetsanding - Fresh Paint vs Factory Paint

Wetsanding - Fresh Paint vs Factory Paint


Hand Sanding the Liberace Lavender Paint on the Titanic - This is a CUSTOM Paint Job



Machine Dampsanding the Joker Truck - This is a CUSTOM Paint Job

Ever since discussion forums starting popping up on the Internet there's always been a fair amount of interest in the topic of wet-sanding either on detailing forums or forums dedicated to a particular type of car, for example Corvettforum.com, a site dedicated to Corvettes.

And as with most topics there's a certain amount of confusion in general about the process, so here's just a tidbit on the topic of wet-sanding that I don't see addressed in a lot of threads on this topic.

Here's the skinny...
The majority of all wet-sanding is performed on fresh paint, there's no hard statistic but I usually float the percentage of 90% to 95% but admit that I could be off just because of the increased interest in the topic thanks to its popularity on the myriad of different discussion forums all over the world wide web.

Regardless of the exact percentage figure, the bigger picture is that the majority of wet-sanding is performed on fresh paint, not factory baked-on paint.

Here's why fresh paint is more often sanded
  • Fresh paint will tend to be softer.
  • Fresh paint will tend to be thicker.
  • Fresh paint will be sprayed on custom projects with more planning involved and higher expectations.


Here's why factory paint is more often not sanded
  • Factory paint will be harder.
  • Factory paint will be thinner.
  • There is little to zero discussion between the future owner and the technicians and or robots programed to spray paint.


Now lets look at each of these topic in a little more detail...


Fresh paint sprayed at a local body shop

Fresh paint will tend to be softer
Modern basecoat/clearcoat paints are catalyzed, that is they are chemically hardened, a simple analogy would be the way you mix a 2-part epoxy glue together and the resulting product hardens through a chemical reaction. If you've ever worked with fiberglass and polyester resin where a small amount of catalyst, (hardener), is added to the resin and the chemical reaction cause the resin to cure and harden, that's another simple analogy as to how catalyzed basecoat/clearcoat paints are hardened.

Contrast this to older style paints which were called solvent-evaporation paints in which the paints dried without the use of a catalyzing agent and instead simply dried and hardened over a longer period of time as the solvents mixed into the paint evaporated.

Even though most modern paints are chemically cured, there is still a window of time where these paint are not 100% hardened and during this window-of-time the paint is what is sometimes refereed to as still wet, not like in wet gooey paint but as in still soft enough to easily sand and buff.

There are also what are called fast drying, medium drying and slow drying reducers which are solvents for mixing in with the paint to give it a thinner viscosity before spraying. A painter can match their choice of reducer to speed up or slow down the drying time.

All these factors can affect paint hardness or softness in the first few days that follow after the car leaves the paint booth.

Usually, if the painters knows the car is to be wet-sanded after painting he can adjust how he mixes the paint to give the person usually called "The Painter's Helper" time to sand and buff the paint before it becomes too hard. Time of year which includes temperature and humidity can also play huge factors in drying or curing time and can be factored in and adjusted for.

Now here's what's key about this, sanding paint is always easy whether the paint is fresh or baked-on at the factory, in simple terms, (very simple terms for the purpose of explanation), sanding paint is putting scratches into the paint.


Again... sanding paint is easy, it's the part where you try to remove your sanding marks that can be difficult. The harder the paint the more difficult it will be to buff out your sanding marks. The softer the paint the easier it will be to remove your sanding marks.


Fresh paint will tend to be thicker
At the body shop level, again if the painter knows the car is to be sanded and buffed, they'll usually add an extra coat or more of paint, this gives the painter's helper a little more wiggle room to sand and buff and not worry about sanding or buffing through the clear coat and exposing the basecoat.

I've also met painters that will just spray a thicker or heavier coat and only spray 2 coats of paint but through factors they can control they can spray it on thicker and therefore not have to spray a third or fourth coat.



Fresh paint will be sprayed on custom projects with more planning and higher expectations.
If you're having a custom car project painted, for example you spent months and more than likely years rebuilding a classic Mustang and now it's time to get it painted, in most cases you'll be meeting with the painter ahead of time planning out the paint job and it's at this time you discuss with them your expectations. If you want the car sanded flat and then buffed to a high gloss for a true show car finish, (if this is you goal or expectation), then the painter will spray an extra coat or two of paint to provide plenty of film-build for the painter's helper to safely sand the paint flat. They will also build in the cost of the extra materials, (clear paint), time and labor to your bill.

Summery
Fresh paint sprayed at your local body shop, specifically the clear layer, will tend to be thicker than the clear layer that comes from the factory and it will tend to be softer and easier to sand and buff shortly after the car comes out of the paint booth. Because it's thicker there is a little more safety margin or wiggle-room for the person to sand and buff the paint and not break-through the clear layer and expose the basecoat. Because the paint is fresh it's going to be softer than factory baked-on paint, at least for a window of time and this will make buffing out the sanding marks faster and easier.



Factory baked-on paint

Factory paint will be harder
The original paint sprayed onto your car as it traveled down the assembly line at the manufacturer's plant is in most cases baked-on at high temperatures before any wiring or the interior is installed and for this reason higher temperatures can be used since there's nothing to melt of catch on fire in or on the car yet. By the time the car pops-out the end of the assembly line the paint is fully cured and hardened. For this reason it will still be easy to sand, (that's putting scratches into the paint), but it will be more difficult to remove your sanding marks out of the paint.



Factory paint will be thinner
At the factory, the paining process is very automated and the amount of clear paint applied to the vehicle is done so in a tightly controlled manner and to very stringent specifications. You don't have the ability to ask for an extra coat of clear, or for a thicker coat of paint to be sprayed and from a materials cost point of view, it's probably safe to say that the amount of paint used to coat each car trends towards being the minimum amount, not a generous amount. Simply put, factory clear coat paints tend to be very thin compared to what you can get at your local body shop.



Summary
Factory paint will tend to be hard and thin, it will be easy to sand but more difficult to remove your sanding marks out 100%

Factory paint will be thin and if you're not really careful you'll break-through the clear layer and expose the basecoat or color coat either during the sanding process or the ensuing buffing process as both procedures remove a little paint.


The above is usually the portion that's left out of most threads on this this topic as it's discussed around the web on the various discussion forums. My theory is because it's left out of so many discussions on the topic, a lot of people don't understand the above differences in types of paint, (fresh vs factory), and that's why you'll often see someone posting that they're interested in sanding the orange peel on their factory finish till its' removed, (till the surface is flat), and then trying to remove their sanding marks, often times with a PC style polisher.

That's just my theory... but I've participated in a lot of these types of threads and when point about the differences listed above it's usually an eye-opener for those thinking about sanding their car's factory hard and thin paint.


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Old 10-28-2009, 12:24 PM   #2
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Re: Wet-Sanding - Fresh Paint vs Factory Paint

Nice write up.
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Old 10-28-2009, 07:57 PM   #3
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Re: Wet-Sanding - Fresh Paint vs Factory Paint

Thanks Mike,

This writeup could not have come at a more opportune time as I am in the midst of battling with the Cadillac dealer over the very same issue.

It all happened when my car was scratched while in for a factory recall. No problem they sent it to their body shop for a repaint of the effected body panel. The car cam back with the panel all hazed and swirled up. it was sent back to the body shop. Then it came back with the panel over worked as if it were being made ready for a show. There was no orange peel in the panel and it looked great. But now it didn't match the texture of the rest of the factory finish so I inquired with the body shop that did the work as to what polish he used that was able to remove the orange peel. I wanted to buy some and do the rest of the car on my own, so it would match. the ownere of the body shop informed me that he wet sanded the panel and offered to wet sand and blend the adjacent panels so it all matches.

Well thanks to Chad of Rasky's Detailing for his advice and knowledge on the subject the dealer is having the body shop only redo the panel that they messed up so that it matches the factory texture on the rest of the car and not touch any of the adjacent. panels.
Oh for all of my inconvenience they are going to repaint my front bumper, that has some chips, at no charge.

I am going to bring a copy of this post into the dealer when I pick up the car this week.

I just want to end by saying thanks to all that make this forum possible. As a result of all of the knowledge and advice that I was able to obtain from this forum my 2009 Cadillac Escalde's paint job is not going to face a potential failure of the clear coat as a result of an incompetent dealer/body shop.
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Old 10-28-2009, 11:36 PM   #4
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Re: Wet-Sanding - Fresh Paint vs Factory Paint

Hey Mike I ran into some clear on my mustang that had a fender replaced and had the hood re-cleared and the adjacent door. The clear on my hood is ROCK hard, I mean like it takes some power with the Flex/orange/m105 to remove marks/swirls.
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Old 10-29-2009, 12:10 AM   #5
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Re: Wet-Sanding - Fresh Paint vs Factory Paint

Quote:
Originally Posted by Superdutytd View Post
Hey Mike I ran into some clear on my mustang that had a fender replaced and had the hood re-cleared and the adjacent door. The clear on my hood is ROCK hard, I mean like it takes some power with the Flex/orange/m105 to remove marks/swirls.
I have found the newer Mustangs have hard clear. I wonder what they used to re-clear your hood. Normally a re-paint ends up having softer clear.
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Old 10-29-2009, 07:46 AM   #6
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Re: Wet-Sanding - Fresh Paint vs Factory Paint

Quote:
Originally Posted by Superdutytd View Post
Hey Mike I ran into some clear on my mustang that had a fender replaced and had the hood re-cleared and the adjacent door. The clear on my hood is ROCK hard, I mean like it takes some power with the Flex/orange/m105 to remove marks/swirls.
And that's why I wrote,

Fresh paint will tend to be softer


Repaints can be as hard or harder than factory paints but the context of what I wrote has to do when the sanding is performed.

At the body shop level most sanding and buffing is done within a few days while there's a window-of-time where the paint is still easy to sand and buff.

On discussion forums, people that have never wet-sanded before get the idea they're going to sand down the orange peel on the factory thin, factory baked-on clear coat that's completely and fully set-up and case hardened.

Huge difference.

Even so, a painter can adjust different variables when they mix the pant and spray paint that's hard to work on within days.

This just drives home the importance of doing a TEST SPOT before sanding down the entire panel or car.

I've been telling this story for years, maybe someone can dig it up on this forum or MOL but it has to do with a Yellow Ferrari. The paint was so hard that it could be sanded, but the sanding marks could not be removed. The painter ended up re-painting the car using a different paint system.

You never know if a paint is hard or soft until you actually go out into the garage and work on it by doing some testing.

Here's another story where I came across a a clear that was very hard. I posted the incident on page 2 of the below thread.

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Old 10-29-2009, 08:25 AM   #7
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Re: Wet-Sanding - Fresh Paint vs Factory Paint

Here's another story that ties in with this that I'll make a dedicated thread later...

Test first, better safe than sorry...

One time I was asked to sand a buff a new paint job for a car that was going to be on a TV show. At the time they were shooting the Pilot. 2-3 other real pro detailers were also asked to help sand and buff the car and get it perfect.

When I arrived at the shop I have to admit I was intimidated to take any kind of leadership position for the project because these guys are easily some of the best in the industry. So I kind of lingered and took on the position more or less of helper guy.

As we started, we had a meeting and these two gentlemen discussed sanding the car down and then buffing it out. No where did they bring up the idea of doing any kind of testing first.

My mind instantly went to the Ferrari incident and the Titanic incident and I thought to myself, I don't want to sand down a paint job only to be embarrassed because we can't get our sanding marks out. This was a new paint job but it was already a month old. While I didn't think this worst case scenario would play out, I would rather be safe than sorry.

So I spoke up.

I suggested we test a small area by sanding it and then see what it will take to get the sanding marks out.

These other two guys looked at me like I was from Mars?


I then simply explained it was just to dial-in a successful system that we could all duplicate over the entire car and be confident in our results but also get the job done faster since we would know exactly what was needed to get the job done.


They both thought that was a good idea so I grabbed a rubber floor mat out of my 1973 Blazer and also a plastic milk crate from out of the back of the Blazer and placed the plastic milk crate on top of the rubber floor mat so could stand on it to reach the roof where I could do a little sanding and buffing.

The Milk Crate is something I usually have in the back of my truck to hold things like 4-way wrench, work gloves, blocks of wood, come-a-along, etc and by itself it's slippery on concrete, but if you place a rubber floor mat on the ground first you can then safely stand on the milk crate and not worry about it sliding out from under you.

Back to the story,
I chose the roof just in case something went wrong it wouldn't be so apparent to the non-paint people involved. These people on this set were car guys, but mostly about the kinds of things you bolt-on, not about the paint work, so just to be extra, extra careful I chose to do the Test Spot on the roof.

So I sanded down a small section about a foot square starting with #1500, followed by #2000 and stopped. I knew I could go to #2500 and then #3000 if I needed to but wanted to see if I could pull #2000 first just as a test and as an indicator as to the hardness of the paint.

Guess what? The paint was hard.

Not over-the-top hard but pulling #2000 grit sanding marks with a W-4000 wool cutting pad and either M84 or M85 was slow and hard. It was doable but now we all knew what we were up against.

We proceeded and did our finish sanding using #2500 and then #3000 and this made the buff-out faster and easier. We spent more time up-front in the sanding step but saved time in the buffing step and the finish came out show car quality.

And just to note, these other two guys really are tops in the area of wet-sanding and buffing with a rotary buffer. I'm confident under different circumstances they would have tested first before starting the job, sometimes when you're out of your normal comfort zone, (working on a TV set), you move in different directions without even realizing it.

As for me, I just wanted to know from the very get-go what we were up against based upon some experience in the past dealing with unknown paint hardness.

So test, test test and don't get yourself into a situation that you can't get yourself out of.


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Old 10-29-2009, 09:12 AM   #8
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Re: Wet-Sanding - Fresh Paint vs Factory Paint

This thread topic reminds me that I can't wait till spring so AG will offer some Detailing 102 classes.

I am looking forward to adding these skills to my repetoire under the skilled guidance of the Not So Cruel Master, Mike P.

Although I don't detail for a living, these skills may give me the confidence to tackle my rock chips myself.
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Old 10-29-2009, 02:05 PM   #9
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Re: Wet-Sanding - Fresh Paint vs Factory Paint

I need to get down to Florida for this class, its just hard to get to the VERY SE corner of the country from the VERY NW corner of the country.
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Old 12-11-2009, 05:20 AM   #10
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Re: Wet-Sanding - Fresh Paint vs Factory Paint

Quote:
Originally Posted by Mike Phillips
So test, test test and don't get yourself into a situation that you can't get yourself out of.
Man that is really GOOD ADVICE
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