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The Auto Painting Tips Newsletter
With Chris Curwen & Expert Auto Painter - Dave Gage (Car Cosmetics) September 4th, 2007 - Issue 19 In this issue:
In the event of performing a partial paint job, 70% of the work will involve preparing the surface, the remaining 30% will be for the actual paint application. When performing a complete paint job however, 95% of the work will involve preparing the surface with only 5% being spent on paint application. Many people do not realize that the condition of the body surface prior to applying paint will have a direct impact on the outcome of the finished paint job. You will be able to see every single particle of dirt, sanding scratch, pinhole or blemish once the paint has been applied over the top of it. The perfect, flawless quality of the surrounding paint will draw the eye to every imperfection. It doesn't matter how many coats of paint you apply, with paint being such a thin layer, flaws on the surface will still be very noticeable. Again, it is vitally important that you properly prepare surfaces before you begin the painting process. When you perform a complete paint job, all of the exterior body trim has to be removed from the vehicle. This includes door handles, trim pieces, mirrors, emblems, badges, key locks, radio antennae and anything else that is attached onto the body of the vehicle. This takes less time compared with trying to mask each of the items ready for painting. Remember, if you don't mask such items adequately, you risk covering them with over-spray. Removing all of the trim ensures your paint job will be even and that none of the trim will cause the paint to build-up or be too thin in cover where parts shield panels. The trim on a vehicle should ideally be removed using the appropriate hand tools to remove nuts, bolts, and screws holding them in place. Only use the proper type of screwdriver or tool for removing each individual piece. You might have to use an adhesive remover to remove other accessories held in place by adhesives or double-backed tape. It is important that you take your time removing all these items as you don't want to risk damaging or breaking them when disassembling them. You'll soon begin to build quite a collection of parts once you start taking them off. In addition to the door handles, key locks and trim, you are going to need to remove the light assemblies, the reflectors, grille pieces, bumpers, license plates, mudguards and more. It is crucial that you devise a system for storing all of these items as you take them off your vehicle to prevent them from getting damaged or mislaid. It is a good idea to have several storage containers on standby to place the parts in as you take them off body areas. This meticulousness will enable you to put them back on after the vehicle has been painted without too much trouble. Keep the fastening nuts, bolts, screws and clips attached to the pieces they belong to at all times whilst they're separated from the vehicle for fast and easy reassembly. Resealable small plastic bags work great for temporary storage of small pieces and parts. Don't forget to use a magic marker to note the contents on the storage label. Be prepared to spend a great deal of time sanding down every square inch of the vehicle or specifically the area that needs it, before you are ready to use a spray paint gun. You need to remove every imperfection on the panel so that your paint will have a blemish free surface in which to bond to. Paint is not thick enough to cover up sand scratch swellings or pinholes, primers are commonly used for this purpose. You will also need to sand primer as it needs to be as smooth as possible in order for the paint to be coated evenly and look visually attractive. When dealing with a Color Change Paint Job there are many factors to be considered before changing the color of a vehicle. It can be a harder process on some vehicles than with others. Keep in mind that a complete color change will require you to paint the engine compartment, door jams and portions of the interior. With most of the sheet metal within the engine compartment obstructed from view, it would still be quite obvious if the sheet metal was a different color from the rest of the car. You should therefore carefully consider the idea of your vehicle undergoing a complete color change if you don't plan on completely disassembling it. The engine compartment, in order to be painted correctly, would require you to remove the engine and all of the accessories, thoroughly clean the compartment using a steam cleaner and then carry out the standard sheet metal prep work. Some people are very skilled with a detail gun and masking procedures and may not have to go to this extent, but it is likely you will need to remove the engine for the best results. If there is no engine in the vehicle that you are working on then of course you can start straight away with the sanding and surface preparation. You will also need to investigate the areas of the interior that need to be removed as well. ******************************************************************************** Questions & Answers: Our first question this week comes from Ronald Divino: Q: What is the difference between primer-surfacer and sealer? A: After sheet metal has been repaired and received coats of epoxy primer where necessary, sanding scratches may still remain on the surface. To cover them, use primer-surfacer products, remembering to use the same brand as the rest of the paint system you are using. Because of its high solid content, primer-surfacer covers tiny surface imperfections and will allow you to sand the coated surfaces to smooth perfection. Primer-surfacer should only be sprayed on surfaces to fill very slight sand scratches or other tiny blemishes. It's a final means by which to sand smooth body surfaces to perfection. Sealers protect undercoats from the materials and solvents in subsequently applied paint top coats and add maximum adhesion capability for those top coats. Sealers will also ensure uniform color match. When applying new paint over an existing paint surface, you must consider the use of a sealer, especially when you are not exactly sure what type or brand of paint is currently on the vehicle. Most sealers do not require sanding after they've been applied and cured, they simply form a sort of barrier between the undercoat and top coat. ******************************************************************************** Our second question this week comes from Eric Tellier: Q: What would cause primer to "curl" in certain places on the surface? I tried to prime my truck but the primer ended up not sticking at all and curled terribly. I could peel it off like a weird tape, what happened? A: The layer of primer is separating from the surface of the vehicle because of a lack of physical bonding. Checklist: * Check if this defect is on the whole unit or in specific areas. * Check other units to determine if a pattern exists. * Check for contamination such as oil, sanding residue, over-spray, water, solvent cleaner residue, etc., on substrate prior to primer application. * Check for non-sanding or etching primer. * Check that the correct amount of hardener was used. * Check for poor surface preparation prior to primer application. * Check solvent selection (too fast). * Check for incompatible products. ******************************************************************************** Our third question this week comes from Patrick Clarke: Q: I currently have a maroon red Honda Civic hatchback and wish to spray it blue do you have any advice? I was also wondering about surface prep, the paint is already in good condition and I want to remove it, how deep do I have to sand it down? A: You really don't have to remove the paint, no need to make unnecessary work for yourself. The original paintwork needs to be lightly sanded, using 800-grit wet and dry sandpaper, this will provide a sufficient base for new layers to bond to. Any repair work should be carried out, only prime the areas that require it, then apply the new color. ******************************************************************************** Our fourth question this week comes from Ray Hussain: Q: Do you have any data on what types of spray guns should be used for applying base coats, primer and lacquer? Any info on the correct PSI settings and spray fan settings? A: A little difficult this one Ray. You see various countries use different types/makes of spray guns, here in the UK we generally use either (Sata or DeVilbiss GTI's). As for the setup, well there are many types dependent on what types of paint you are using. Again here in the UK, most body shops only use water based paints and HS lacquers. My advice would be to speak to your local paint distribution center and ask them the same question. Sorry we can't be of any more help Ray. ******************************************************************************** Our fifth and final question this week comes from Russ Hawkins: Q: I have a 1974 Challenger that currently is painted enamel red, underneath is the original b5 blue metallic enamel. Is there anyway to paint this with lacquer without taking it to bare metal to do so? A: If the enamel is a synthetic based product then you can't apply 2k clear coat over the top, it will cause crazing. ******************************************************************************** That's all we have for you this week. Thank you very much for reading. We both hope this issue has been of valued interest to you. COMING NEXT ISSUE: How to Select the Color. Happy Painting! Chris Curwen & Dave Gage www.LearnAutoPainting.com © 2007
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