My first wet sanding experience

[Legacykid]

So I went to a junk yard in search of a hood, to only find a door. So I decided to give wet sanding a shot. I watched a few videos online, AMMONYC video with Jrose and KBrown was one of them easy to follow. Read up on MPhillips and figured lets do this. I got 1500,2000,3000 grit. I only let them soak for about an hour, because we made the purchase the same day. My GF and Friend were with me to give this a shot as well. We washed and clayed the door.

The car door is an off white with not many scratches in it, so I figured I could key it. Well I went to crazy and got to deep with the first mark. The next time I went a little easier and barely scuffed it. So I let them do the same.

Now we all taped off a section and got to work. I did 1500 - 3000. while my friend did 1500-2000-3000. We did not use a block, which would have been so much easier. Because it is tough to focus on the paint, hand pressure, and make sure your doing it evenly around the work area. I couldn`t believe how hard I was able to push on it and not to much paint was coming off, I figured sand paper would just tear through the layers, leaving no room at all for error, especially in the hands of a rookie.

So I decided to push the limits on the first key mark I made. It was about an inch long so I worked that one area with one finger back and fourth.I went from about 150um to about 130um. I remember reading clear coat is unsafe usually at around 80um. So I had some wiggle room. I went back at it for maybe 10-15 seconds of moderate to hard rubbing to then find this!



So I checked my PTG:


About half way between the gauge and the clear coat failure is the point of measurement:



About half way between the gauge and the clear coat failure is the point of measurement:


As you can see things escalated quickly! Now I followed up with M105 with an orange CCS pad, then M205 with a white CCS pad. Loos what happen to the point of failure as I continued to polish. I did about 2 passes with M105, and maybe 1.5 passes with M205 for reference I used a GG6 with 4in pad speed 5, then speed 3.5.



Anyway here is the outcome of the general area we did.



All in all it was a good experience for me. something I think any detailer, enthusiast or pro, should try out. It is a lot of work that goes into it, and doing it correctly, taking off the least amount of paint, leaving texture or removing orange peel. Much respect to the pros. Anyone doing this kind of work for cheap is crazy and should hold them selves to higher standard. It really is an art that I now have so much respect for.

[Accumulator]

Legacykid- Glad to hear you experiment went so well!

Note that the "safe amount to remove" that you quoted is a *lot* more than Ford recommends taking off though (and they use a lot more clear than some manufacturers). They say their clear fails if you take off something like 16 microns (what I read was in Mils and it was, IIRC "less than 2/3 of a Mil"). Yeah, I know..lots of people take off far more than that.

[Legacykid]

Legacykid- Glad to hear you experiment went so well!

Note that the "safe amount to remove" that you quoted is a *lot* more than Ford recommends taking off though (and they use a lot more clear than some manufacturers). They say their clear fails if you take off something like 16 microns (what I read was in Mils and it was, IIRC "less than 2/3 of a Mil"). Yeah, I know..lots of people take off far more than that.

Good to know, do you have any reading on this? I am still confused how some cars come off the lot with 200um, and some come with 130um.

also I guess I should mention this was a door from a GMC denali.

[Stokdgs]

What is interesting to me is the measurements you were showing and I assume that these were measurement numbers AFTER the break through of the clear coat ??

Did you first, calibrate your gauge, have a new battery in it, and then take readings all over the door to get a baseline ?

I NEVER believe or use any number as the SAFE amount to remove - Ever.... remember this IS the Internet...

Way too many variables that can never be all accounted for..

Most gauges unless they are the most expensive DeFelsko gauge are going to be a little inaccurate and can only be used as a baseline number that you want to be comfortable with, and then, this is critical - you have to keep measuring - in Microns - to see if that base line number goes down and then stop when it does...

A block would have made this less dangerous because hopefully you checked it and it is absolutely flat all the way across and sideways, and used it correctly..

Any part of your hand is going to be much more dangerous and will always leave the surface uneven, which will look bad when viewed from the side, even if its polished beautifully.. It just wont be perfectly straight and flat there...

It IS a lot of work and noting the higher grit numbers paper, of course you are removing very little at a time, and you cannot get impatient, and ruin the work requiring now a re-paint...

Perhaps working with or finding information from very good Painters who do this work for a living, would be beneficial as well.. They would also have all the different sized tools, blocks, sword brushes, etc., and be able to show you how its really done..

The ones with the gray hair are going the be the ones with the most experience and wisdom...
Dan F

[Legacykid]

What is interesting to me is the measurements you were showing and I assume that these were measurement numbers AFTER the break through of the clear coat ??

Did you first, calibrate your gauge, have a new battery in it, and then take readings all over the door to get a baseline
Just calibrated, not a new battary or anything. I use it as a way for me to feel more comfortable, this is a cheaper tool but has been proven to work well enough. Overall numbers were about 150-160 across the panel.
I NEVER believe or use any number as the SAFE amount to remove - Ever.... remember this IS the Internet...

Way too many variables that can never be all accounted for..

Most gauges unless they are the most expensive DeFelsko gauge are going to be a little inaccurate and can only be used as a baseline number that you want to be comfortable with, and then, this is critical - you have to keep measuring - in Microns - to see if that base line number goes down and then stop when it does...

A block would have made this less dangerous because hopefully you checked it and it is absolutely flat all the way across and sideways, and used it correctly..

Any part of your hand is going to be much more dangerous and will always leave the surface uneven, which will look bad when viewed from the side, even if its polished beautifully.. It just wont be perfectly straight and flat there.. I have to look at this I never thought of that!

It IS a lot of work and noting the higher grit numbers paper, of course you are removing very little at a time, and you cannot get impatient, and ruin the work requiring now a re-paint...

Perhaps working with or finding information from very good Painters who do this work for a living, would be beneficial as well.. They would also have all the different sized tools, blocks, sword brushes, etc., and be able to show you how its really done..

The ones with the gray hair are going the be the ones with the most experience and wisdom...
Dan F

^^

[Accumulator]

Good to know, do you have any reading on this? I am still confused how some cars come off the lot with 200um, and some come with 130um.

also I guess I should mention this was a door from a GMC denali.

Sorry, I don`t have a copy of the info (got it from Ron Ketcham, who was invovlved with this stuff when he worked for ValuGard and was working hand-in-hand with the major automakers).

Yeah, CC/paint thickness can vary a *LOT* between makes, some Japanese vehicles have incredibly thin clear that could never withstand wetsanding (or even aggressive compounding or polishing, as I found out the hard way on my Mazda MPV).

The clear on my GM SUVs has always been fairly thick, but not thick enough that *I* would take off that much. But hey, I`m really conservative about it.

IMO the big "gotcha!" here is that if you take off too much you generally won`t know it for a while...until UV exposure takes its toll. Well, unless you take of *way* too much But even then, it`s sure not a matter of just not "going through" the clear.

[GearHead_1]

Cool beans. Love to see that kind of research.

[jerry r]

Sanding any paint is hard, but when you get into oem it takes a keen eye and plenty of practice to get it right every time,doing it by hand is going to bite you in the ass eventually,most likely on a black car because as has been pointed out by Stokdgs, the grove that you put in with your finger will be visible at the finish,my current weapon of choice is dry sanding with this kit I got from cartec,and because its a dry sand system I can see things in real time as apposed to wiping off each time to see were I am,i cant upload any photos to the site,its 2 air sanders that use 2 inch sanding pads going from 1000 grit to 4000 grit

[Accumulator]

jerry r- I suspect people are leery of using the sanders, but I think that 2" setup you have sounds great. And finishing out the sanding with 4K sure makes for easy compounding/polishing, huh?

[jerry r]

jerry r- I suspect people are leery of using the sanders, but I think that 2" setup you have sounds great. And finishing out the sanding with 4K sure makes for easy compounding/polishing, huh?

Its very easy to use safely Accumulator the finish you get with the 4000 is mighty and Cartec supply the compounds along with the 2 inch hard pad [orange] and the 2 inch soft pad [black waffle pad] and I have the correct backing plates to fit my rotary ,i already use their 4800 and their 12000 compounds and have to say I find them really good, especially on hard clear as I do a lot of German cars I save a bit of time.
its made easy with the two air guns, one is da and one is direct drive and are very comfortable in the hand

[Woob]

Definitely use a block or a DA, by hand is more of a feel aspect for curves since it`s easier to contour. General measurement for removing too much factory clearcoat is removing more than 25% of clearcoat fill build where uppermost UV protection is present. There are ALOT of variables that come into play in the factory painting process (clear coat used, amount, etc). 0.5 mils is where I would suggest stop[ing, you`ll see just how aggressive/fast you`re removing the finish and know when to stop. Cars can read from 80-200 microns all the time, it`s where you start from the beginning and where you end. Most importantly is what the operator & client want. I`ve seen people do 1500 grit to level contours/remove OP, and STILL see some waviness due to the painting process. Factory paints are thin...

References: Ron Ketchum of Auto International, Professional Car Wash & Detailing Magazine.

[WhyteWizard]

Personally, I think everyone who wants to detail cars should do some wetsanding for the purpose of getting correction down. After you`ve sanded a few cars, correction is a vacation.

Robert

[Accumulator]

Woob- Nice to see your note regarding Ron Ketcham!

jerryr- Ah, interesting...didn`t know about Cartec. And I agree that the milder papers/etc. are simply great for serious work. Not just for time savings but also because *IMO* properly done *very gentle* wetsanding can, in some cases (gee, lots of qualifiers huh?) actually remove less clear than aggressive compounding. That said...

WhyteWizard- Heh heh, I myself wish that the vast majority of detailers would just *NEVER* remove as much clear as typical wetsanding involves. Hey, I do it so I`m not being a complete [jerk] here, but in my area clearcoat failure is downright endemic and one can often see *exactly* what "detailing" lead to it. Clearcoat`s primary function is to protect the basecoat; looking nice and marring-free is a *very* distant second-place consideration IMO.

[jerry r]

Woob- Nice to see your note regarding Ron Ketcham!

jerryr- Ah, interesting...didn`t know about Cartec. And I agree that the milder papers/etc. are simply great for serious work. Not just for time savings but also because *IMO* properly done *very gentle* wetsanding can, in some cases (gee, lots of qualifiers huh?) actually remove less clear than aggressive compounding. That said...

WhyteWizard- Heh heh, I myself wish that the vast majority of detailers would just *NEVER* remove as much clear as typical wetsanding involves. Hey, I do it so I`m not being a complete [jerk] here, but in my area clearcoat failure is downright endemic and one can often see *exactly* what "detailing" lead to it. Clearcoat`s primary function is to protect the basecoat; looking nice and marring-free is a *very* distant second-place consideration IMO.

Good advice Accumulator,people do tend to rely on it a bit to much when they get confident,i only use it as a last resort,or as is usually the case when I see the scratch I will know straight away that it needs to be hit with a sanding,i have a bottle of stuff I picked up along the way from Ferecla its used to key up paint before its resprayed, its like 1500 in a bottle, so I will sand an area then 1 pass with the Ferecla then the normal compounding,and of course the end result will show up the area that has been sanded compared to the rest of the car so care has to be taken as to where its used,imagine sanding the middle of a bonnet [hood] on a black car then get to the finish only to see a glass finish in the middle and the rest is op,not good,but then every day is a school day.

[Angus]

Thanks for the write up! Picking up a junk yard test panel to try out a little wet sanding in the comfort of my basement sounds like a good winter project.