Here's how to do a "Section Pass" when trying to remove swirls, scratches and other below surface paint defects.
How to do a Section Pass
[ame=http://www.youtube.com/watch?v=Q70g83mnTn4]YouTube - How to do a "Section Pass" with a Porter Cable 7424XP[/video]
When talking about machine polishing on discussion forums or even in detailing classes, the below questions always comes up,
- What's a pass?
- How many passes do I make?
- What's a section pass?
The definition of a pass
There are two definitions of the word pass as it relates to machine polishing with any type of machine.
Single Pass
A single pass is just that. It's when you move the polisher from one side of the section you're buffing to the other side of the section you're buffing. That's a single pass.
Section Pass
A section pass is when you move the polisher back and forth, or front to back with enough single overlapping passes to cover the entire section
one time. That's a section pass.
In most cases if you're removing any substantial below surface defects you're going to make 6-8 section passes to the section you’re working before you either feel comfortable you've removed the defects or you're at the end of the
buffing cycle for the product you're using.
Buffing Cycle
The buffing cycle is the amount of time you are able to work the product before the abrasives have broken down, (if you’re using a product that uses diminishing abrasives), and/or the product begins to dry and you lose the lubricating features of the product. Different products have different buffing cycles depending upon the type of abrasives used in the formula and the different ingredients used to suspend the abrasives and provide lubrication.
Factors that affect the buffing cycle include,
- Ambient temperature
- Surface temperature
- Size of work area
- Type of machine
- Type of pad material
- Humidity
- Wind or air flow surrounding the car
- Amount of product used
- Technique
Wet buffing technique
Most compounds and polishes should be used so that there is enough product on the surface to maintain a wet film while the product is being worked. The wetness of the product is lubricating the paint as the abrasives abrade the paint and cushion or buffer the abrading action so the abrasives don’t simply scour the finish leaving behind swirls and scratches.
Dry Buffing Technique - Buffing to a dry buff
There are some products on the market where the manufacture recommends buffing the product until it dries. As the product dries you’ll tend to see some dusting as the product residue becomes a powder and the paint will have a hard, dry shine to it.
Although some manufactures recommend this, it’s important to understand what’s taking place at the surface level as you buff to a dry buff. As the product dries, in essence you are losing the lubricating features of the product and as this happens friction and heat will increase. As friction and heat increases, so does the risk of micro-marring the paint or instilling swirls either by the product residue or the pad material and/or a combination of both.
While we trust that the manufacture knows their products best, when we take a close look at what it means to buff on a delicate surface like an automotive clear coat, it doesn’t make sense to run a buffing pad on top of the paint
without some kind of wet film to lubricate the paint at the same time. We always recommend that you follow the manufacturer's recommendations and use your own judgment.
Everyone new to buffing wants to be told some easily identifiable sign that they can use to tell when it's time to stop buffing and it's not that simple, so here's an indicator I've always used and taught to others,
Wet film behind your path-of-travel
As you're making a single pass with the polisher, the paint behind the path of travel of the buffer should have a visible wet film on it. If the paint behind the pad is dry and shiny, you've run out of lubrication and you're dry buffing. Turn the polisher off. Wipe the residue off and inspect using a Swirl Finder Light to make sure you didn't dull or mar the paint, you usually won't cause any harm, but pay attention when your running the polisher and don't buff to a dry buff. If you do, you can quickly re-polish that section by cleaning your pad and adding a little fresh product and making a few new section passes.
UMR
Remember, in most cases the goal is UMR or Uniform Material Removal. The reason for this is so that you remove an equal amount of paint over each section and in turn over the entire car. In order to do this you need a method that you can control and duplicate and for most people following a back and forth, side-to-side pattern works because it’s easy to remember, easy to do and easy to duplicate.
Resources
The above video segment is a 4 minute clip filmed during the extended version of
How To Remove Swirls using any Dual Action Polisher like the
Meguair's G110v2 and the
Griot's Garage ROP and all models of he Porter Cable Dual Action Polisher, including the
PC7424XP, PC7424, PC7336, G100
How to Remove Swirls using the Porter Cable 7424XP or any D.A. Polisher
