Many of the principles discussed here also apply to Wool pads



Foam Pads



Under a microscope, foam pads look like a bee`s honeycomb, small uniformly shaped cells. The smaller the cells the more densely the construction (higher PPI), this type of foam pad would be considered less aggressive, thus it would be considered a finishing pad. The opposite effect takes place if the foam cells were larger, or less dense (lower PPI). This construction will cause the foam pad to be more aggressive, as in a compounding pad.



Pads made of high strength reticulated (artificially broken-in) foam. In other words, the cells are open; this allows air to flow through the foam. Chemical compounds and polishes require the right amount of air flow through the foam. Open cell foam is ideal for this process to succeed. Not only is closed cell foam not ideal, but it is structurally weaker.



The features that distinguish quality foam pads; the use of various, engineered polyether polyurethane reticulated foams imported from Europe, that are specifically designed for machine compounding, polishing and buffing Engineered refers to various levels of abrasive ability or grit number rating.



As a result of improved foam manufacturing technologies, foam pads have made great advances in performance and durability. Like their wool counterparts, foam pads must be properly cared for to insure consistent performance. The vast majority of domestically produced foam is designed for air filtration, not machine polishing.



Foams from third world countries that supply low cost foam cannot match the quality, performance and consistency of European specialty foams that are manufactured to ISO 9000 quality standards.



The pads used at the OEM level worldwide (Audi, BMW, Daimler-Chrysler, Ford, GM, Porsche, VW, etc.) including those produced by 3M are all made from European foam (the majority of which is supplied by Reisgies Schaumstoffe, Global Minority Business Network (GMBN) Leverkusen, Germany) In most cases, these foams are substantially more expensive than domestic foams due to currency fluctuations, ocean shipping, and customs duty and import tariffs.



If you`re looking at a modestly priced pad at your local auto parts or department store, it’s highly unlikely that they are made with quality European foam.



Foam pads perform differently from each other on the basis of how they’re constructed. Under a microscope, foam pads look like a bee’s honeycomb, small uniformly shaped cells. The smaller the cells the more densely the construction, this type of foam pad would be considered less aggressive, thus it would be considered a finishing pad. The opposite effect takes place if the foam cells were larger, or less dense.



This construction will cause the foam pad to be more aggressive as in a compounding pad. There are various grades of foam pads on either side of the aggressive or finishing scale.



The face of a polishing pad should be designed to efficiently use its surface contact area. If a foam pad has lines, squares, circles, or dimples cut out of (or pressed into) the pad face, less actual surface area is available compared to a flat pad. Usually these foam patterns are designed to increase buffing performance by the slower release of product, operator comfort or ease of use as they decrease the contact area and the pads efficiency



Periodically inspect the face of your foam pads, eventually you will have to replace the pads as they will wear and lose their abrasive ability just like finish paper



A flexible backing plate and a foam pad with a cut-out design can be of benefit when dealing with surface contours and angles as they tend to conform to these shapes better than a plain flat pad, they also tend to transfer less heat. They also provide an extra level of cushioning while polishing curved surfaces, distributes pressure evenly over the contact area of the pad, they are less aggressive than a more rigid backing plate and will help to reduce swirls



When trying to remove deep sanding scratches, especially if they are close to an edge or a seam a stiffer backing plate is advantageous

The most efficient polishing method is a flat pad applied with consistent pressure; this ensures the surface area of the pad is used efficiently, in a similar way to wet-sanding with finishing paper and a sanding block



Trailing and Leading Edge



Looking at a pad that is on the paint surface; the trailing edge is the left side (between 7and 5 o’clock) and the leading edge is the right side (between 11 and 1 o’clock)



A light sensitive approach is essential, using only the weight of the machine, on vertical panels just enough pressure to maintain contact with the surface (without applied pressure) use a lower speed 1000 – 1200 RPM and keep the pad moving. Tilt the contact edge of the pad a few degrees so that only the leading edge of the pad is in contact with the paint surface. Make sure the leading edge (right hand side) of the pad on a rotary polisher is rolling off the panel so that would mean the right side of the pad is rotating off the panel.



If you have the trailing edge (left side) of the buffer on the edge it will tend to strongly force the machine out of your hands and burn the edge almost instantly.



Grit Numbers



Sandpaper or finishing paper is the most common item from a larger group of products known as "coated abrasives" i.e. Aluminium oxide.

When talking about "grit" is a reference to the number of abrasive particles per inch of finishing paper (sandpaper). The lower the grit the more abrasive and conversely, the higher the grit number the lesser (smoother) the finishing paper



When talking about abrasive finishing paper, "grit" is a reference to the number of abrasive particles per inch of paper. It eliminates the risk of deep sanding scratches by providing a uniform grit size. This makes sense if you imagine how small the grit particles on a 1000-grit finishing paper would need to be to fit into a 1- inch square. Grit finishing paper is referred to by the size of its abrasives (i.e. 1500-grit paper) the grit you use depends on what you are trying to do.



Foam Pads are also rated on a grit number, that is to say the scratches they will remove after using grit finishing paper along with a similarly rated polish (i.e. 2500 grit rated pad and polish combination will remove the marks left after using 2500 grit finishing paper)

Auto polishes and compounds have a grit number associated with them. This is the level of grit made on a paint surface by finishing paper on newly applied OEM paint on the production line i.e. before it has been oven dried and cured



Be cognizant that both polish / compound and pad grit numbers are referenced to a rotary polisher using wool pads (to the best of my knowledge they have never been changed to suit orbital polishers or foam pads)



Select an abrasive polish to match the scratch you are trying to remove. It makes no sense to use a very aggressive polish, that will remove most scratches but at what cost to clear coat thickness. Both foam pads and polishes have a grit number) most polishes will state the level of scratch removed by stating grit numbers i.e. will remove 2000 grit scratches caused by using 2000 grit finishing paper



Once you have identified the scratch ‘grit’ marks you can match a polish and a foam pad (i.e. 2500 grit marks, require a polish that is capable of removing 2500 grit (number) marks, matched with a suitable cutting pad (e.g. Menzerna Power Finish (PO203S) this is a one-step scratch remover polish that will remove 2500 grit, matched with a LC White light cutting foam pad)



1000 < grit Heavy - (Compound) levels and removes heavy defects

1200 grit Heavy - levels moderate to heavy defects

1500 grit Medium - levels light to moderate defects

2000 grit Moderate - levels light defects and removes hazing

2500 grit Light - levels swirl marks, light defects and removes hazing

3000 grit Fine - very minor corrective ability, burnishes paint to high gloss



Priming Pads



If you were to apply polish to a body panel, and then place a pad on the surface and turn the machine on, it would be very difficult to control and will produce surface hazing. This is due to most of the pad being "dry". Polishes and compounds appear to work better when the foam pad is ‘primed’ some things to note about pad priming: the cutting ability is increased, a better finish is obtained, it reduces any product ‘flashing’ problems, it produces a more even finish and the polishing machine is less likely to hop. Use a very slightly distilled water dampened pad, not too wet (otherwise the polish will clump); then spread the polish / compound over the pad evenly and ensure it is absorbed into the foam



Do not use a quick detailer (QD) as a pad primer medium as most are formulated with either a wax or a polymer; however they are not easily adaptable to a spray formula. To be efficient they need to be emulsified to work as a spray, to facilitate this they need to use an emulsion of silicone oils and water. The wax will reduce the friction heat, negatively impacting the diminishing abrasives; silicon-based products can also have a negative effect on the surface / polish lubrication oils used causing surface smearing.



As a polish or a compound uses either oil, wax or a polymer as a lubricant the water content of a quick detailer (80 – 90%) is not miscible and therefore acts as a buffer between the pad and the polish negatively affecting the abrasive abilities of both diminishing and non-diminishing abrasives.



Pad Seasoning



To season a primed pad, spread the polish / compound over the pad evenly and ensure it is absorbed into the foam, and then spread that polish onto the pad by hand until it becomes (80%) saturated. To apply to the paint surface; lightly raise the back of the machine so you are working with the top 1/3 of the pad.

After polishing for a minute or two the pad will become more evenly saturated with product and actually become softer from heat build-up (seasoned). At this point, you can safely transition from a tilted up to a flat polishing position. Every time you put a fresh pad on your machine you should prime and then season it for a minute or two before "flat" polishing.



Contact Area



A pad should be designed to efficiently use its surface area. Foam pads that have lines, squares, circles, or dimples cut out of the pad face, means that is less actual surface area in contact with the paint surface. Area = π(r2) 6-inch pad area = 18.842 sq.ins (see also backing plate)



Another design parameter that determines how much surface area actually contacts the paint when using foam pads is the amount of pores per inch it features (commonly referred to as PPI). More pores, larger pores, thinner walls between the pores, or how stiff the walls are all affect how much foam contacts the paint during the buffing process



Block wet sanding (finishing paper and a sanding block) which ensures a consistent pressure over the surface contact area, this is the most effective tool for paint defect removal because of its linear process you abrade the paint surface flat until the defects are removed.



Surface Area



The distance around the circle is a circumference. The distance across the circle is the diameter (d). The radius (r) is the distance from the centre to a point on the circle. (π = 3.14), d = 2(r), c = π d = 2 (p) r, A = π(r) 2



Pad Velocity



The larger the pad, the greater the pad velocity at an identical RPM; a smaller pad is less aggressive for the same reason V = RPM (Area) A - 6.5-inch = 20.423 sq.ins V= 24,507 inches per minute (IPM) A - 8-inch =25.136 sq.ins. V= 30,163 IPM



Pressure / Pad Compression



Depending on the types of surface abrasions you`re dealing with, increase pressure as necessary. Just remember that more pressure equals more aggressive, so be careful around ridges and raised surfaces Maintain the same pressure and work the product in, it may take three or four passes to complete before the residue can be removed. Once you see the desired results move on to the next area, or repeat the process as necessary.



The required pressure applied to obtain optimum results to adequately compress the pad (50%) and obtain uniform abrasion is usually in the range of 10 – 15 lbs. (a random orbital buffer will stall at approximately 20 pounds of applied force) To compress a 6-inch pad 50% requires you increase the total force by the ratio of its surface areas Ratio = [π (radius2)] / [π (radius2)] = 2.25 as much force, almost 34 pounds).



With the smaller pad you`re applying the same force, at a constant speed but over a smaller, more concentrated area, which will induce friction and greater abrasion abilities to the polish, both these abilities require a certain amount of caution as it’s possible to abrasion burn the paint.



Foam Pad Size (Area and Applied Pressure)



Smaller pads in general will offer you more control with any polisher, as it can reduce the tendency for it to skip on the paint surface. Smaller pads also make it easier to manoeuvre in tighter areas and closer to trim pieces.



Assuming equal speed, radius and foam compression (50% - 15 pounds of force applied) the difference between 4- inch and 6 - inch pads is their different surface area = π (r2) (4-inch = 12.46 sq.ins / 6-inch = 28.26 sq.ins) and therefore surface kinetic (or dynamic) friction applied and surface pressure applied 4-inch = 3.75 lbs per sq.ins. 6-inch = 2.5 lbs per sq.ins.



Kinetic (or dynamic) Friction



Kinetic friction induced heat is an often misunderstood concept of polishing / compounding; some abrasives require friction to breakdown, not heat; heat is just a resultant of friction between two surfaces.



Polishing a paint surfaces transfer’s kinetic (or dynamic) friction induced heat to the paint surface, thermoplastic polymers have both tensile strength and elongation (elasticity) which allow the surface to flex, expand and contract in accordance to surrounding temperatures, solvents, resins and other ingredients in polishes will expand causing the paint film surface to expand.



As the metal substrate expands the paint moves with it, due to its elasticity, thereby becoming elongated (thinner) this is part of the cause of friction induced ‘burn’, you’re applying pressure and an abrasive to a less dense (‘thinner’) paint surface.



Pad Cleaning



All pads have a performance cycle, meaning you will get the desired results only to a certain point. That point of declining performance is typically caused by compound overload. With proper cleaning this situation can be avoided.



Pads must be cleaned after each use to insure a decent life expectancy, but the use of improper cleaning tools can do more harm than good. The wrong tool can cause the wool to unravel; as the tufts unravel, the pads performance is reduced.



Most car care products contain oils that serve as surface lubricants. Even if you rinse the pad immediately after using it, the oily residue remains because oil and water are not miscible. To properly clean the wool or foam pads, you need to use a cleaner that contains a degreaser (P21S Total Auto Wash).