Hand Polishing FASTER Than Machine???

[AutowerxDetailing]

Over the weekend I had the opportunity to help with one of the WORST water spot removal projects I have ever been involved with. I believe it was an '08 Acura MDX. The paint was rock hard and the water spots were etched and layered from years of neglect.

Sorry... no before pics of the water spots. We threw everything we had at this paint. PCXP, Griots DA, HD DA, Flex 3401VRG, 849x, Rupes 21, LC Orange, LC Yellow, MF cutting discs, M105, M101, M100. The water spots simply would not budge. They eventually came out after roughly 15-20 passes but here is the weird part: the areas that needed to be done by hand where the polishers could not reach seemed to come out much easier. I'm not saying it was effortless. My arm currently feels like it's going to fall off; however, by hand it almost seemed to be correcting the water spots faster than was occurring by machine.

I am having trouble figuring out WHY this would be the case... How could it be that the back and forth motion of polishing by hand would actually correct BETTER than any of the machines we tried, including the rotary???

Please, someone enlighten me with a scientific explanation because I don't get it.

 

[psnt1ol]

I am not a physicist but I do believe it has to do with surface area. I am sure someone will correct me if I am wrong.:dblthumb2:

When you polish by hand, the pressure is generally not evenly distributed throughout your hand. Most of the force is near your finger tips. Your finger tips has very small surface area so in short.... the same force apply (pound per square inch) increases as the surface area shrink. It is a similar effect of running a 3" pad on a DA vs a 6" or driving a nail with a hammer through a board.

 

[davey g-force]

Perhaps those tighter areas just weren't as badly spotted as the rest of the car?

Just a thought...

 

[Harry Da Hamster]

I just saw the pix in the other thread. In this situation, maybe a wet sand would've been best? It probably took so long cause you're not cutting paint, you're cutting minerals and other junk.

 

[Theraven]

More force and pressure is concentrated in the area you are polishing by hand. Tried a rotary buffer?

 

[hernandez.art13]

I am not a physicist but I do believe it has to do with surface area. I am sure someone will correct me if I am wrong.:dblthumb2:

When you polish by hand, the pressure is generally not evenly distributed throughout your hand. Most of the force is near your finger tips. Your finger tips has very small surface area so in short.... the same force apply (pound per square inch) increases as the surface area shrink. It is a similar effect of running a 3" pad on a DA vs a 6" or driving a nail with a hammer through a board.

Make sense (don't know if it's true )

View attachment 21162

^ he can probably answer this mystery

 

[HateSwirls]

Interesting

 

[Mike PhillipsMike Phillips is verified member.]

You can exert more pressure with a few fingers pushing down against an applicator pad than you can apply to the face of a foam pad on a dual action polisher.

I'd say for some instances, working by hand is more effective than working by machine, in the big picture it's not faster overall.

I actually have a lot typed about this on MOL, just go over there and do a word search using the word,

Exert


It's the same reason why you can remove sanding marks by hand next to raised body lines or edges but you certainly wouldn't want to remove all the sanding marks over an entire car by hand as it would tear up your arm.

Removing sanding marks can be thought of as the same type of thing you would do if you were removing water spots or normal swirls and scratches...

The Rule of Thumb

Here's a shot of removing sanding marks by hand. My hand is blurry in this picture because it's moving at the speed of light.

Removing Scratches By Hand


I induced straight line scratches by hand, then ran a tape line across the paint, then worked the scratches out by hand using Wolfgang Total Swirl Remover, (4 well worked applications), followed by Wolfgang Finishing Glaze, (2 gentle applications), then striped with 17% IPA

I try to do all my work by machine but there are some places a buffing pad on a machine can't get to or it's risky.


How to remove wetsanding scratches by hand - FG 400


Anytime you're wetsanding a car there will be places you cannot easily or safely get a rotary buffer and a buffing pad to remove your sanding marks. In these situations you need an aggressive compound that you can use by hand.

The trick is to remove your sanding marks while not scouring the paint from the abrasives used in the compound. If you leave light or shallow scratches that's okay because the tricky and important goal is to be able to remove the sanding marks, you can always refine your results using a finer polish applied by hand.

For the wetsanding, cutting and buffing project on the mystery car this weekend there will be places where it will be risky to remove sanding marks using a machine, at least the initial cut.

So before leaving the well equipped Autogeek garage, I machine sanded one of our black paint panels and then tested the new Menzerna FG 400...


Paint panel machine sanded using #3000 Triazact...

Use a cloth applicator with a nap
To make any compound or polish more aggressive use a cloth applicator pad or cloth material that has a nap. The larger more stout the nap the more aggressive the abrading action.

Chemically stripping the paint
Looks great before chemically stripping so lets strip the paint to make sure the sanding mars are in fact removed. I don't care if there are toweling marks because I expect that from the pressure I'm going to be applying when rubbing the paint hard to remove small particles of paint.

Removing clear coat paint by hand requires putting some pressure behind the pad...

Sanding marks removed, only fine or shallow toweling marks remain...

Close-up cropped out of the above shot...

Chunk of masking tape to give my camera something more definitive to focus on...

From another angle you can see the flash of my camera lighting up the paint but you can also see how distinct the 4 florescent tube lights are overhead.

Here I've pushed the panel closer to the work bench to capture a reflection of the holes in the peg board...

Success!
We'll be using Menzerna FG 400 to cut out our sanding marks for the wetsanding project this weekend and for the areas we cannot safely buff by machine we can use FG 400 by hand. Yancy says he can capture this on video too...


It comes down to the force you can exert to a small area together with a fast hand motion to work the abrasives over the paint. When you push the abrasives against the paint you force them to take little bites out of the paint and thus remove the defects.

 

[Mike PhillipsMike Phillips is verified member.]

I wrote this back in 2009, it's an example of the BIG PICTURE as it relates to TIME when comparing what you can do by hand and what you can do by machine.


Man versus Machine

 

[AutowerxDetailing]

Thanks for the answers everyone!! That makes a lot of sense about the pressure being focused on the smaller area (your fingertips) when working by hand.

 

[statusdetailing]

Lately, I've just been doing a quick damp sand with a 3000 grit disc, followed by 105 on a mf cutting disc, when I come across severe defects. I think this can actually save time in the long run when dealing with severely neglected paint. That way you're not having to do a million passes when compounding.

 

[Mike PhillipsMike Phillips is verified member.]

Lately, I've just been doing a quick damp sand with a 3000 grit disc, followed by 105 on a mf cutting disc, when I come across severe defects. I think this can actually save time in the long run when dealing with severely neglected paint. That way you're not having to do a million passes when compounding.

Isolated Defect Removal

This is actually a class and a concept I teach at Mobil Tech Expo showing how to use the Griot's Grage 3" Mini Polisher as a "Dampsander". The below is from this last year's classes, note the 4th class down the list...



Autogeek Class Schedule at Mobil Tech Expo 2013


Here's a list of my classes, location and times...


Thursday January 17th, 2013 – Education Day

How to detail a car – Order of steps - 9:30am to 10:15am Oleander Room
The order in which you tackle a detailing project can either help you or slow you down. When detailing cars for dollars time is money. You will learn which areas of the car to detail first to reduce the total time invested in any detailing job to maximize profits while reducing overall time per detailing project. One of the most common problems detailers make is duplicating steps, which wastes valuable time.


Detail Faster with the Flex XC3401 - 11:45am 12:30pm Sawgrass Room
There are a lot of tool options available for making money detailing cars. Each type or category of tool has its strong points and its short comings. You will learn how to turn the Flex 3401 Forced Rotation Dual Action Polisher into your own money making machine when doing production detailing and even show car detailing.


How to properly use the Rotary Buffer - 12:45pm to 1:30pm Sawgrass Room
The rotary buffer is without a doubt, the most powerful tool there is for machine polishing cars, trucks, boats and Motorhomes. It’s the tool of choice for removing sanding marks after wetsanding an entire car or an isolated repair. The rotary buffer is also to blame for the majority of all the holograms you see all too often in a car freshly detailed by Dealerships, Body Shops and “yes” even supposedly Professional Detailers. You will learn tips and techniques gained over a lifetime from using the rotary buffer including compounding with wool pads, polishing with foam pads and jewelling paint for a hologram-free finish.


Isolated Scratch Removal - 3:30pm to 4:15pm – Sawgrass Room
With the introduction of high quality, ultra fine grit sanding discs, you can now remove isolated defects by safely sanding them out and then safely removing your sanding marks. Performed correctly, no one will ever know there was a defect or that the area was sanded and buffed. You will learn tips and techniques for dampsanding using 3M and Meguiar’s #3000 and #5000 finishing discs and then how to quickly remove all traces of the sanding procedure.



Microfiber Pads - 4:30pm to 5:15pm - Sawgrass Room
Microfiber pad technology is the new hot trend for machine polishing paint and in this class you will learn how to match the right pad to the right tool to get the best performance out of microfiber pads. You'll also learn product selection to match the right chemicals with your microfiber pads for specific paint polishing procedures. Plus how to clean your microfiber pads on the fly to keep them working at maximum efficiency throughout your detailing project.



Renewing Exterior Trim - 5:30pm – 6:15pm Sawgrass Room
So many new cars, trucks and sports utility vehicles utilize plastic, rubber and vinyl trim to reduce both weight and costs when manufacturing new vehicles. The problem with exterior trim material like this is it fades, oxidizes and turns ugly gray with repeated exposure to outdoor environments, UV rays from direct sunlight, and the drying out effect from repeated car washing and inclement weather. In the past most dressings were topical and would easily wash off. Advances in technology has introduced a new selection of exterior trim dressings that last longer and look better for customer pleasing results.



Friday

No Classes on Friday Saturday, January 19th, 2013


Saturday


How to detail a car – Order of steps - 11:30am to 12:15am Oleander Room
The order in which you tackle a detailing project can either help you or slow you down. When detailing cars for dollars time is money. Learn which areas of the car to detail first to reduce the total time invested in any detailing job to maximize profits while reducing overall time per detailing project. One of the most common problems detailers make is duplicating steps, which wastes valuable time.



:xyxthumbs:

 

[zmcgovern45]

From a basic engineering point of view...

Pressure = Force / Area

For simplicity sake, let's compare the area of a 3" pad to 4 fingertips. I am going to say a fingertip is a perfect circle with a diameter of approximately 2 cm (or ~0.8") to make things easier.

Since we know that the Area of a cirlce = pi (π) * r², we can calculate the surface area of both the pad and fingertips. Therefore the area of a 3" pad = π*1.5in² = 7.1 in² and the area of 4 fingertips = 4*(π*0.4in²) = 2 in²

Now... for simplicity sake, let's assume that you are exerting the same amount of force for both the 3" pads and when you are polishing by hand - Somewhere around 15 lbs.

Calculating the pressure based on our known force and areas, we see that the pressure exerted on the painted surface by the 3" pad is approximately 2.11 lb/in² (psi) compared to the calculated 7.5 lb/in² (psi) therefore you are getting over 3.5X the pressure when polishing by hand vs. using a 3" pad (again, assuming you are exerting an identical amount of force in each instance).

This is why 3" pads are great for spot treating RIDS compared to 6.5" pads... the smaller area exerts much more pressure onto the surface without the addition of any extra force from you.

-Zach