Wetsanding vs. Rotary vs. PC, what removes more paint? (The answer may shock you)

Dave1 said:
Hmmm.....



I'm thinking April fools on this diagram......



Maybe the whole show........
Click to expand...



I'm not sure why you think that. If you have to remove a certain amount of paint to reduce defects, wouldn't it make sense to do it the most precise way possible?



The diagram is crude (at best) but I only did to show what I believe is happening (at a microscopic level).
 
TH0001 said:
I'm not sure why you think that. If you have to remove a certain amount of paint to reduce defects, wouldn't it make sense to do it the most precise way possible?



The diagram is crude (at best) but I only did to show what I believe is happening (at a microscopic level).
Click to expand...



It's the "chasing scratch theory" that has me thinking on this 1st day of April......



My wife has already tried today. She called and explained in detail about the guy who rear-ended her on the way home from work.......Had I not been used to these performances, I would have been sick.....



Anyway.....what is the volume of pressure exerted on the floor of the scratch from the applied force from above.....?



Does a compound exert more pressure than sanding residue inside the same framework....?



Do pad selections and their firmness absorb the hydraulic properties of the scratch chase contention.....?



I don't know.......I'm just pondering these new destructive clear coat forces the PC now seems to be accused of........:D
 
Dave1 said:
It's the "chasing scratch theory" that has me thinking on this 1st day of April......
Click to expand...



My wife has already tried today. She called and explained in detail about the guy who rear-ended her on the way home from work.......Had I not been used to these performances, I would have been sick.....
Click to expand...



No joke, sorry...



Anyway.....what is the volume of pressure exerted on the floor of the scratch from the applied force from above.....?
Click to expand...



No idea, its just a theroy.



Does a compound exert more pressure than sanding residue inside the same framework....?
Click to expand...



I would imagine that the pressure exerted by pressing a pad and compound down would be far greater then the gliding the of the flat surface. I would imagine it is almost zero to none.







Do pad selections and their firmness absorb the hydraulic properties of the scratch chase contention.....?
Click to expand...



I would imagine that a softer pad would do more chasing, though this would probably occur less on a rotary since the you are planeing the surface.



I don't know.......I'm just pondering these new destructive clear coat forces the PC now seems to be accused of........:D
Click to expand...



There is no desctructive force. If you need to remove paint, you need to remove paint. If you have to remove .02 mils, the only question is which process gives you the ability to remove .02 mils the most precisely.



If you don't believe that pads and compounds "chase" perhaps you would explain to me why you can't buff away orange peel?



Most RIDS and swirls we see are microscopic in depth, and this needs to be kept in prespective. As the paint around the microscopic scratch is removed, there is going to be contact between the depth of the scratch and the pad. I've heard body men discussing chasing scratchs for a long time, so I am suprised this is the part of my theory that is even questioned.
 
Macruz19 said:
Geez... I wish I had the skill to wetsand and use a rotary so I understand better.
Click to expand...



Come on down to Orlando and I'll show you how to do both.



I will also do what I did with Pats300ZX (the moderator) and prove to you that SIP and 106ff fill (ask Pat).
 
TH0001 said:
SIP and 106ff fill (ask Pat).
Click to expand...



This is true.....



Anything that has some cut will in esscence fill the left over inclusions on the surface with residue from the work performed......



A rinse or "flush" is required to remove any residue left inside the inclusions. Certain cleaning agents may require a dwell time after a flush for the product to flash or dry before a another product is applied. A heat lamp will accelerate dwell times when necessary for certain applications......
 
I was also thinking about this. I used some 3m3000RC by my Ridgid and orange pad to remove some sanding scratches It did a remarkable job but left a slightly hazed surface so I had to 3 step it. On another section i tried the same 3m compound by rotary with a german green pad and it left a better surface so I was able to go direct to my finishing polish. My theory is that the hard Aluminum Oxide abrasives break down much faster by rotary. With a RO they perform more of a sanding action as they break down. That is why IMO the PC can remove more clear than a rotary with heavy duty compounds.
 
I have to agree with Todd on the D/A vs. Rotary in chasing. Since the rotary works much faster than a D/A at correction, you are able to flatten the surface in a shorter amount of time, thus preventing the pad from dipping down into the crevice (persay) of the scratch and thus "chasing" the scratch further and further into the surface. Its crude logic, but it does make sense. (to me at least.) I dunno, maybe im wrong.
 
wannafbody said:
I was also thinking about this. I used some 3m3000RC by my Ridgid and orange pad to remove some sanding scratches It did a remarkable job but left a slightly hazed surface so I had to 3 step it. On another section i tried the same 3m compound by rotary with a german green pad and it left a better surface so I was able to go direct to my finishing polish. My theory is that the hard Aluminum Oxide abrasives break down much faster by rotary. With a RO they perform more of a sanding action as they break down. That is why IMO the PC can remove more clear than a rotary with heavy duty compounds.
Click to expand...



Hmmm....



Ok, so your RO was sanding and your rotary was cutting.......(basically from your post)



Did the sanding action remove more cc than the cutting action....? (pads were different, so it's hard to tell here IMO)



Two steps are nice but, is it possible that the first rotary step removed more scratches from the surface than the RO did....?



Heavy compounds with a rotary can do some serious paint damage in a hurry if your not careful. Heavy compounds with a RO will not do as much damage as quickly using the exact same products .....IMO
 
Very interesting test. I agree with your theory that wetsanding gives you greater control so you stop the instant the RIDs are gone.
 
Dave1 said:
Hmmm....



Ok, so your RO was sanding and your rotary was cutting.......(basically from your post)



Did the sanding action remove more cc than the cutting action....? (pads were different, so it's hard to tell here IMO)



Two steps are nice but, is it possible that the first rotary step removed more scratches from the surface than the RO did....?



Heavy compounds with a rotary can do some serious paint damage in a hurry if your not careful. Heavy compounds with a RO will not do as much damage as quickly using the exact same products .....IMO
Click to expand...



It also has to do with the hardness of the abrasives. Aluminum Oxide is very hard and takes more friction to break down.
 
mrfjsw294 said:
I have to agree with Todd on the D/A vs. Rotary in chasing. Since the rotary works much faster than a D/A at correction, you are able to flatten the surface in a shorter amount of time, thus preventing the pad from dipping down into the crevice (persay) of the scratch and thus "chasing" the scratch further and further into the surface. Its crude logic, but it does make sense. (to me at least.) I dunno, maybe im wrong.
Click to expand...



but why wouldnt the rotary chase the scratch?
 
very interesting results and it does follow logically. whenever you have a decent scratch on a car and you polish it with a da or forced rotation machine you see that the scratch gets less noticeable but that the "walls" of the scratch spread a bit too as you work it. so where before it was a sharp thin line, it starts to become a less defined wider line.



if the line gets wider, it makes sense that you're removing some material from the valley of the scratch as well. and if you're using a pc you're going slow enough that you could really work that low part. a rotary probably spins fast enough that it's more likely to shave the top off rather than work the whole thing down.
 
GREAT write up. Made me think completely different about how precise wet sanding is.. So should I be less or just as worried about wet sanding an entire panel of my car (say a door) with 3000 making only 5-8 light passes on the whole door to remove OP/Scratches/Swirls/Rids ect. Then polishing out the sanding marks. Should I be worried about this taking away too much clear and removing the UV protection in the CC that the factory left behind? I am eager to wet sand some spots on my e30 that have more OP than others but did not want to remove too much CC and cause failure later down the road. I have all sand paper in my aresenal from 1500 to 4000. I would be doing this by hand and using optimum polishes/compounds and a purple LCC wool pad to remove the sanding marks.

Thanks.

TH- You REALLY know your stuff. I apriciate you always posting in depth well educated responses to everything on this forum. It has really help save my detailing process so much!

-Nick
 
Can You Hear Me said:
GREAT write up. Made me think completely different about how precise wet sanding is.. So should I be less or just as worried about wet sanding an entire panel of my car (say a door) with 3000 making only 5-8 light passes on the whole door to remove OP/Scratches/Swirls/Rids ect. Then polishing out the sanding marks. Should I be worried about this taking away too much clear and removing the UV protection in the CC that the factory left behind? I am eager to wet sand some spots on my e30 that have more OP than others but did not want to remove too much CC and cause failure later down the road. I have all sand paper in my aresenal from 1500 to 4000. I would be doing this by hand and using optimum polishes/compounds and a purple LCC wool pad to remove the sanding marks.

Thanks.

TH- You REALLY know your stuff. I apriciate you always posting in depth well educated responses to everything on this forum. It has really help save my detailing process so much!

-Nick
Click to expand...



great question i am interested in this also
 
Good stuff. This also brings new light to wetsanding and the differences in Rotary vs PC. Which are often ambiguous at best.



I understand your theory, and ultimately I think it was said best that settling for a little less than perfection is the best option. 96% is good enough if it saves alot of the paint. imho.



But, its good to chase a hypothesis..



So wetsanding with 3-4k paper is really, ultimately, safer and removing less than a Rotary or RO with an agressive compound? My question is how much pressure is (average, or appropriate) when wetsanding with this method.



I think it makes a valid point that with a RO you are at the mercy of the speed of the polish breakdown. At any point during that breakdown the correction can and is being made. At points after the made correction you are removing unnecessary paint. RO is not an exact science, not by a longshot. But it is safe enough that you remove a little excess to achieve perfection without the dangers of cutting too much.



The rotary does this much faster, and you can back off a little sooner and wipe to check.



Technically you can back off the RO and wipe before it has completely broken down, but if it isn't to your liking, you have to reapply new and break down completely again. Removing more than you previously would have.
 
You must log in or register to reply here.
Back
Top