Not understanding the differences in sanding methods.

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jta98z

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Hey guys. Happy Thanksgiving. I was reading something the other day that said dry sanding was meant for factory paint while wet sanding was meant for repaints. I'm fairly confident I've seen guys wet sand factory paint. Can you guys substantiate this claim?
 
I don't believe he is asking about sanding fresh from the factory paint. In general, is one type of sanding reserved for one type of paint, while the other for another?
Is wet-sand strictly for paint-shop/body shop paints?

One scenario I can think of to sand factory paint is to level orange peel.
 
If I hand sand, I go with a wet system, If I use a da, I use a dry system with a interface pad.
 
rescuenut10 said:
If I hand sand, I go with a wet system, If I use a da, I use a dry system with a interface pad.
Click to expand...

Using a da is awesome to knock all the orange peel down flat. I used to do it all by hand until I discovered the da. I wish I would of bought one years ago
 
When I do da sanding, I try to blow off the surface and sand paper regularly to avoid build up scratching the surface.
 
I don't think dry sanding is that bad. Renny Doyle teaches dry sanding in his course. I believe Mike Philipps also put out a video recently where he was dry sanding a car.

Wet sanding is more efficient because it prevents the paper from clogging.
 
hamlyn said:
I don't believe he is asking about sanding fresh from the factory paint. In general, is one type of sanding reserved for one type of paint, while the other for another?
Is wet-sand strictly for paint-shop/body shop paints?

One scenario I can think of to sand factory paint is to level orange peel.
Click to expand...

Right. That was the gist of my question. I hadn't heard of anyone dry sanding paint and didn't know why it was specific to different paints.
 
There are benefits to both dry and wet, sometimes it comes down to personal preference.

If you dry sand though you should wear a air filter mask so you don't breath saned paint particle into your lungs. This is why I normally wetsand as the paint particles are trapped in your water slurry with less chance of becoming airborne.

Dry sanding makes checking the level of peel removed faster as you don't have to wipe away water and wait for any water film to flash evaporate before you can see the peel/no peel difference. Like this,

Dry Sanding Results
3M_Flexible_Abrasive_Hookit_Sheets_P1500_006.jpg





The new flexible 3M Hookit sheets are made using some type of no-loading technology, it seems to work pretty well.


Here's a few recent threads on this topic with pictures to boot...

Dry Sanding & Wet Sanding with 3M's Flexible Abrasive Hookit Sheets

Here you go... pictures showing the sanding sheet being cleaned using terrycloth...



Here you can see the single stage yellow paint on the face of the Hookit sheet.

3M_Flexible_Abrasive_Hookit_Sheets_P1500_007.jpg



A quick wipe with a clean, terry cloth towel and the paint residue wipes almost completely off. You can use compressed air too...

3M_Flexible_Abrasive_Hookit_Sheets_P1500_008.jpg





Here's another with some great pictures...

Removing #1500 Sanding Marks with Rupes Bigfoot 21 Polisher


Now I've zoomed in and you can see the orange peel on the right side where I did not sand and how the paint starts to flatten out as you look to the right side of the picture.

Removing_1500_Sanding_Marks_Rupes_002.jpg




And another article with pictures of both dry sanding and machine wetsanding...


Pictures: 1928 Model A - Wetsand, Cut and Buff at Autogeek



Den wetsanding the curve of the roof...
It's always great to have Den here to help with these projects. Sometime in the near future we're going to have Den's GTO here for a show car makeover.

1928_Model_A_Coupe_023.jpg






:)
 
^^ Wow. Thanks a lot for the in-depth response Mike. I really appreciate that. Reading over some of these articles now.
 
jta98z said:
^^ Wow. Thanks a lot for the in-depth response Mike. I really appreciate that. Reading over some of these articles now.
Click to expand...


No problemo...

I'm impressed with the new 3M Flexible Hookit sheets. They need to make the Velcro backing pad available by itself so I can have more than one in the garage so more than one guy can hand sand with a single box of #1500 flexible sheets.

That said, they don't go any higher at this time than #1500 so for me I'll still want to finish out by hand using #3000 and/or #5000


I'll have these available at my next detailing boot camp class in January for students to test out.



:)
 
Mike,
Can you elaborate on your choice of grit progression (whatever it may be) when sanding...wet or dry?
 
Hoytman said:
Mike,
Can you elaborate on your choice of grit progression (whatever it may be) when sanding...wet or dry?
Click to expand...



What a coincidence...


A guy named Frank called me from Canada with the same question after watching this video...

How to wet sand a car​

[video=youtube_share;5zDuFzvKSAI"]How to wet sand a car[/video]​


The full write-up plus all the before and after high resolution pictures can be seen here,

How to wet sand a car - Time Lapse Video


Basically follow the sage advice of,

"Use the least aggressive product to get the job done"


I also told him it's a bad idea for most people to sand on factory paint because it's thin to start with and making it thinner increases the risk of clearcoat failure down the road.

Also told him to remember this,


  1. Sanding removes paint
  2. Compounding removes paint
  3. Polishing removes paint


If the paint you're working on is thin to start with then there's not much room for error.

Also told him this,

Words cannot explain the heart sinking feeling you get when you turn your buffing pad over to see the color of the basecoat coming off onto the face of the pad.

For those that might not understand, if you're working on a clearcoat finish and you start to see the color of the basecoat on the face of your buffing pad or worse, in your sanding dust or sanding slurry, this is a sign you've went past the point of no return.


Then told him that if he is going to sand on factory paint to stick with the higher grit finishing papers or finishing discs.

For working on custom paint job, locate the painter and ask the painter how much paint he sprayed, try to get the big picture answer from him like,

"I sprayed plenty of clear"


Also find out if he or anyone else has already sanded and buffed the paint.

The idea here is to find out how much paint was sprayed if any has been removed already.

In all the years I've been teaching classes on wetsanding here's what I've found out...

Guys want to learn how to wetsand. It's as though it's in our DNA.

Once a person learns how by for example, sanding down an entire car and then buffing it out, most people don't ever want to do it again.

Here's the kicker... the only way to get it out of your system is to learn by doing.


These guys were so tired after they had the blessing of wetsanding from start to final buffing, this GTO here at AG.



1971 GTO - Wetsand, Cut and Buff




Here's a few more complete wetsanding projects brought to you by the AGO Discussion Forum and Autogeek.net


The Patrol Car

Pictures: Wetsand, Cut & Buff 1971 Fury Police Car!



The 1963 Impala SS

Pictures and Comments - January 26th & 27th 2013 Detailing Boot Camp Class




The 1928 Model A Hotrod...

Pictures: 1928 Model A - Wetsand, Cut and Buff at Autogeek



Jay's 1989 Yenko Blazer...

Episode #13 of Autogeek's What's in the Garage on this Sunday!



Here's one Matt and I knocked by ourselves...


1956 Chevy Bel-Air - Dampsanding, Cut & Polish






:)
 
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