Achieving a showroom gloss – removing paint defects
For the very lucky few, or those with the use of a professional spray booth with filtered air input, all that may be required after spraying will be a quick once round with a fine hand-glaze polish to bring out that deep, dazzling gloss.
For the rest of us, here’s what comes next.
Compounding can be carried out by hand, but the use of an air or electric powered buffing machine will save hours of hard work. Avoid prolonged rubbing in one spot, or along edges or pressed creases in panels, as it is surprisingly easy to take all the paint off. Users with a power polisher will also need to take care that the machine is kept moving constantly, otherwise heat generated can melt, damage or change the colour of the paint. Judicious use of a hand-spray containing water helps to keep polishing heads cool and damp.
Compound, as it is generally known by the trade, is an abrasive paste available in various grades, from very coarse (flatting paste) through medium, to fine and ultra fine. All work by removing a very thin layer of paint, coarser grades work faster but leave visible scour marks, whereas fine grades remove very little but leave the surface glossy. Depending on make, they can be water or solvent based, liquid or paste. For use on new or recent paintwork, only medium grades upwards would be used. Coarse grades are more appropriate for rapid paint or surface restoration in skilled hands.
Polish is more generally used to describe final surface treatments such as wax or silicone, but the term becomes interchangeable, with `polishing’ and `compounding’ tending to mean the same thing to bodyshop staff
Removing surface imperfection by hand or machine
Cellulose and acrylic air-drying paints remain reasonably easy to compound and polish for a considerable time, but 2-pack materials are best compounded initially within a day or two of being sprayed. If left too long, they become very hard and, if flatted, make it extremely difficult to compound out flatting marks. This is even more so if power tools are not available. If 2-packs need rectification by way of compounding, it is best to complete the flatting and compounding stages as soon as possible after initial drying, even if fine compounding is left until later
Rectification of problems in the paint surface obviously depends on the depth of paint and the depth of the problem. Some will compound out without problem, whereas others may be embedded deeper in the paint film rather than simply stuck on the surface. Minor dust specks or slight dry spray can be rubbed out manually or with a power polisher, using a medium grade rubbing compound.
By hand – Most types are applied with a damp cloth, rubbing with normal hand pressure in straight lines until the surface is smooth. Usually this leaves the surface slightly dull, but the gloss will be restored by using a finer grade of compound or polish to finish.
By machine – Damp the compounding mop slightly, and apply a small amount of compound to a section at a time. Use the weight of the polisher rather than press on, taking care on raised panel features. It is best to avoid corners or edges completely. Work a small section at a time, buffing regularly with a soft cloth until happy with the appearance.A hand spray filled with water is useful for keeping the compounding head damp. Wipe compound spots from other panels before they dry.
Removing dust or paint sags – flat and polish
More serious defects, such as larger dust particles, paint sags or heavy `orange peel’ effect can be rectified using ultra-fine wetordry paper , used wet with plenty of soapy water. Use 1200 grade or finer if available, especially on dark colours. A soft sponge rubbing block is best to avoid leaving finger tramlines in the surface. Flat the affected paintwork until the surface is smooth, rinsing the abrasive paper often to avoid damage to the fresh surface. Wiping the surface clean and letting it dry usually shows whether flatting has removed all the defects. Remember, only remove the minimum of paint to level the surface, as restoring the gloss with compound will remove a little more.
Use a medium grade rubbing compound to remove the flatting marks, either manually or by machine. If working by hand, wherever possible rub in straight lines along the panel. Using a circular motion tends to leave swirls which are difficult to remove with finer grades. Use a clean, dry cloth to regularly buff the area to assess progress. When the flatting marks have given way to a gloss, finish with a fine grade compound to remove any swirls left by the previous compound. It is usually best to process one panel or area at a time, otherwise it can become a daunting task, especially by hand. It is possible to flat and polish the whole car in this way, and it produces an absolutely mirror finish when done correctly, but it is time consuming and runs the risk of `cut-through’ in awkward places, requiring further paintwork.
Only when all compounding is complete is it worth considering waxes or other surface treatments. Their use any earlier would be at best a waste of time, and at worst might contaminate surfaces which may need further paintwork.