Wet Sanding????

Beemerboy

Beemerboy

Just One More Coat
I'm perplexed by why some reach for sand paper as a solution to getting the clear coat near perfect, without using less aggressive methods such as wool pad and compounds,where you can control the amount of clear you take off, a tad easier.

My thoughts are with wet sanding you take a fair amount of the clear off, and IMO you run the risk of causing early clear coat failure, or without a good paint gauge can reduce the clear that simple future polishing could break threw to the base coat.


Mr. Clean you do quite a lot of wet sanding, can you shed some light on this for me?


I have done a fair amount of wet sanding but that's only been to take out clear coat level scratches and such.

Thanks
 
I believe with some of the high-grit sandpapers, they can be (relatively) as safe as compounds, wool, and rotaries can be dangerous.

About the only time I use sandpaper is when doing touch ups with paint. I did just finish wetsanding the top cap of my boat to get rid of a couple small oxidation spots, too.
 
I worry more when using a rotary than wet sanding with 2000 you won't burn the paint hand sanding.
The combination of wet sanding and buffing out the sanding marks will combine to make CC too thin.
 
I always try and polish out a scratch first. But 95% when i say wet sanding may be needed I will be right. The only problem I see with some people doing this is they sand a tiny area flat (removing the scratch) and not try and blend the peel to make it a little less noticable ( sanding a little more of the area around the scratch). I normally won't wet sand a car that has been repainted on the pannel I'm working on unless I know of the shop that has worked on it.
 
I agree and disagree.. and will try my best to explain. a bit perplexed? yeah, me to.

Beemerboy said:
I'm perplexed by why some reach for sand paper as a solution to getting the clear coat near perfect, without using less aggressive methods such as wool pad and compounds,where you can control the amount of clear you take off, a tad easier.
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only thing comes to mind is User preference

Beemerboy said:
My thoughts are with wet sanding you take a fair amount of the clear off, and IMO you run the risk of causing early clear coat failure,
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Everything we do here in the wrong hands has the potential to cause clear coat failure.

Beemerboy said:
without a good paint gauge can reduce the clear that simple future polishing could break threw to the base coat.
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ok here is where I would agree with you:
For anyone with out the time and experience and goes straight for a wet sanding process will only create mess. without a good paint gauge can reduce the clear that simple future polishing could break threw to the base coat.
yes.. but not likely, depending on veh manufacture (there are soft clears out there). everyone thinks paint is soft and fragile when in fact it can take a bit more abuse than most expected. (this is not a challenge)
yes.. a Paint Thickness Gauge is a great tool and I have seen them go for $300.00 to $2,000.00 this tool can be very expensive, but cheaper that a paint job. wet sanding preformed properly will remove around 0.2 mils of clear coat after polishing out, you could remove that much with machine polishing a veh several times a year. depending on how aggressive you get with product and pad selection.

wet sanding serves a purpose as well as the woolies the rotary or any other device we use to do our job to find that elusive perfect shine. yes.. wet sanding COULD remove a fair amount of clear coat if preformed improperly.. and even here we exhibit restraint and use the least aggressive paper first. most of us play with paper in the range of 1000(coarse) to 3000(semi-fine) and have seen paper go into the 8000(very fine) range.

With every level of detailing there also comes a level of confidence. junk yard hood, fenders and practice.. practice.. practice


Beemerboy said:
Thanks
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Your Welcome
 
Beemerboy said:
I'm perplexed by why some reach for sand paper as a solution to getting the clear coat near perfect, without using less aggressive methods such as wool pad and compounds,where you can control the amount of clear you take off, a tad easier.
Click to expand...

This is a good question that a lot of less experienced users have. Wet sanding, particularly when done with a hard backing pad that allows the force of the sanding paper to be focused primarily on the high points, is actually far more precise than polishing.

The ability to focus your action on the the high points and remove those is often called leveling. When removing wide defects/imperfections/texture we need something that has extreme leveling to avoid removing paint from the low spots as well.



My thoughts are with wet sanding you take a fair amount of the clear off, and IMO you run the risk of causing early clear coat failure, or without a good paint gauge can reduce the clear that simple future polishing could break threw to the base coat.
Click to expand...

It's hard to say. Lightly wet sanding with 3000 grit sandpaper is likely not anymore aggressive (in terms of total material removal) then using a compound a wool pad, with the added benefit of being able to stop and measure your work frequently and to focus on just the high areas.
 
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While we are on this subject of wet sanding, I have always had the best result from doing a couple of things, after determining this is my only option -
1. Always use a sanding block. There are big 3m rubber ones, and smaller 3m square ones, probably even some round ones.
The block will totally level everything the paper touches perfectly.
2. If possible, spray a little lacquer of a different color lightly, over the area you want to sand.
This "guide coat" will enable you to detect any high and low spots and when its all sanded off, you have a pretty darn flat sanding job which is what you want.

In the auto painting world, we always primed, sprayed a guide coat, and block sanded the area/s down, felt it with our hands, maybe primed again, guide coated, and block sanded all the guide coat off, until we were satisfied that area was perfectly straight.

You could never depend on the Body Guys to finish the repair perfectly - they just dont do it - but they (and the Owner) expected the Painter, the Painter's Apprentice,, etc., to finish the repair to perfection - and we did !!! :)

Dan F
 
Stokdgs said:
While we are on this subject of wet sanding, I have always had the best result from doing a couple of things, after determining this is my only option -
1. Always use a sanding block. There are big 3m rubber ones, and smaller 3m square ones, probably even some round ones.
The block will totally level everything the paper touches perfectly.
2. If possible, spray a little lacquer of a different color lightly, over the area you want to sand.
This "guide coat" will enable you to detect any high and low spots and when its all sanded off, you have a pretty darn flat sanding job which is what you want.

In the auto painting world, we always primed, sprayed a guide coat, and block sanded the area/s down, felt it with our hands, maybe primed again, guide coated, and block sanded all the guide coat off, until we were satisfied that area was perfectly straight.

You could never depend on the Body Guys to finish the repair perfectly - they just dont do it - but they (and the Owner) expected the Painter, the Painter's Apprentice,, etc., to finish the repair to perfection - and we did !!! :)

Dan F
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I can agree with this. I guess it's time to post an opinion. This may gum up but it does give a guide.
 
GEEZ brings back memories! sand, spray guide coat, sand over there, spray more guide coat, get dizzy, sand till it feels smoothe, dont know whats going on till you spray the basecoat, opps, have to break that & resand the primer again & guide coat. i miss those days man!

"2. If possible, spray a little lacquer of a different color lightly, over the area you want to sand.
This "guide coat" will enable you to detect any high and low spots and when its all sanded off, you have a pretty darn flat sanding job which is what you want."

for #2 dan, are you saying to spray a guide coat for wetsanding clear?
if so, ive never heard or done that before.

wetsanding = my fav topic to discuss!
 
love watching a good painter use a guide coat: a 34 foot fountain CC
guidecoat.jpg
 
AndrewBigA said:
GEEZ brings back memories! sand, spray guide coat, sand over there, spray more guide coat, get dizzy, sand till it feels smoothe, dont know whats going on till you spray the basecoat, opps, have to break that & resand the primer again & guide coat. i miss those days man!

"2. If possible, spray a little lacquer of a different color lightly, over the area you want to sand.
This "guide coat" will enable you to detect any high and low spots and when its all sanded off, you have a pretty darn flat sanding job which is what you want."

for #2 dan, are you saying to spray a guide coat for wetsanding clear?
if so, ive never heard or done that before.

wetsanding = my fav topic to discuss!
Click to expand...


Yes I myself have used water based paint on clear for a guide coat.
 
I heard an interesting tip on another forum the other day, suggesting a Sharpie marker be used as a "guide coat" when removing orange peel -- just sand until the pen line is gone and you're at the bottom of the OP. Haven't tried it yet but it sounds like a neat trick.
 
Even with a guide coat it can be hard to get paint completely flat. As the difference between the high's and low's of the orange peel decreases the paper will begin to follow the subtle differences in elevation, so you are effectively sanding the high and low spot at the same time.

How many times have you sanded a spot completely flat, only to buff it out and discover their is still orange peel (although significantly less). What always amazes me is watching an expert with a long block. The way they can maneuver a long block around a car and get it perfectly flat ceases to amaze me.
 
Todd Helme said:
Even with a guide coat it can be hard to get paint completely flat. As the difference between the high's and low's of the orange peel decreases the paper will begin to follow the subtle differences in elevation, so you are effectively sanding the high and low spot at the same time.

How many times have you sanded a spot completely flat, only to buff it out and discover their is still orange peel (although significantly less). What always amazes me is watching an expert with a long block. The way they can maneuver a long block around a car and get it perfectly flat ceases to amaze me.
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I actually saw some block a car for the first time like a week ago, and yeah amazed comes to mind, I have trouble with a 6 inch sanding block let alone a 3 ft one lol
 
Somehow I missed this thread. I honestly hate wetsanding, and rarely do it when working on clients vehicles. At work, I have to. The body men here are horrible, the boss is guaranteed to be the biggest hack in history, and the vehicles here are in terrible shape EVERY time. By the time the boss sends his "touch up boy" out on the lot with a bottle of laquer thinner and a towel to "prep the surface" for the touch up paint, the paint is already shot. Then, they go into the body shop where they are spot painted with single stage and "buffed" the next day. Base/clear you can do that..SS not so much. The body shop doesnt believe in masking anything, so on top of the thinner damage and crappy paint, now there is enough overspray and tape lines on the vehicle that clay wont even glide over it. So, the only resort is to wetsand it or leave it, which i wont do. Trust me, this isnt something i enjoy doing, but i feel that after a couple thousand wetsanding jobs under my belt, Im good enough at it to do it safely
 
Thank you guys. These posts have been very helpful to me. I wet sanded out about a dozen large scratches on a mini-van other other day. Can't wait to try a whole car - I think.
 
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