Going through the grits What does this mean?” No it’s not a reference to eating breakfast in Georgia! It’s a very similar idea to ‘Least aggressive first’ it refers to the process of using different grit finishing papers of progressively finer grit or foam / wool pads with progressively denser pads to get a smooth finish. By going through the grits each progressive piece of grit finishing paper or pad removes the scratches from that previously used. Always start with the least abrasive combination, i.e. a machine polish and the least aggressive foam or wool pad. Always choose the least intrusive product, it is preferable to polish 2-3 times to restore the paint film surface than to use an unnecessarily abrasive machine polish / foam pad combination. Before commencing polishing do a test panel on the car, once you have achieved the desired results with the chosen polish / pad combination proceed 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. The lower the grit numbers the rougher the paper and conversely, the higher the grit numbers the smoother the paper. 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" 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. a) 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 b) 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. 2000 grit rated pad and polish will remove the marks left after 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 1. 1000 < grit Heavy - (Compound) levels and removes heavy defects 2. 1200 grit Heavy - levels moderate to heavy defects 3. 1500 grit Medium - levels light to moderate defects 4. 2000 grit Moderate - levels light defects and removes hazing 5. 2500 grit Light - levels swirl marks, light defects and removes hazing 6. 3000 grit Fine - very minor corrective ability, burnishes paint to high gloss General Rules 1. Porter Cable 7424 random orbital polisher; the limiting factor to pad size is the actual power of the machine. Using larger pads on these machines actually reduces the amount of polishing power due to the surface resistance of the pad, which will cause the motor to slow down or stall. Conversely using a smaller pad will increase the power available by reducing the surface resistance by concentrating motor power on a smaller area. 2. With smaller pads you gain increased control and manoeuvrability. Smaller pads generate more kinetic friction (and subsequently, increased heat) with a PC, which breaks down polishes by generating energy (and applied pressure) over a concentrated area. The random orbiting motion of the PC generates the most power in the centre of the pad (i.e. area of a 6.5 – inch pad is 33 – square inches compared to the area of a 4 – inch pad, which is 12.5 – square inches) This additional pressure / cutting power will facilitate the removal of deeper imperfections 3. The opposite is true with rotary buffers. The speed of the outer edge of a smaller (radius) pad is slower than that of a larger (radius) pad. This helps reduce the amount of friction generated, which makes polishing tighter areas much safer. 4. Do not use the same pad to apply differing products as cross contamination will reduce the effectiveness or completely negate their purpose altogether. A new or freshly cleaned pad must be used with each type of car care product. 5. Water will increase the abrasiveness of a polish; but unlike wool, a foam pad has no fibres to twist, bend, and reshape, therefore helping to loosen the abrasive, so water tends to cause abrasive-clumping, which is detrimental to its performance, it can also cause the pad / abrasive to aquaplane, negating the abrasive 6. There is no recognizable standard between manufacturers that use colour as an identification of the abrasiveness of a foam 7. Apply pressure to the foam; if it springs back the pad is fine. If it stays compressed the foam core is damaged and it’s time to replace the pad. An extract from one of a series of unbiased Detailing Technical Papers, a library of educational materials that has become the #1 reference for car care on the Internet Chances are you'll learn something about detailing if you read any of these; although these articles will not improve your detailing skills, lead to a successful business or change your life. Applying what you learn from it, however, will. That's where your commitment comes in - you need to make a commitment to yourself right now that you will take action on what you learn. © TOGWT ™ Ltd Copyright 2002-2010, all rights reserved
