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Prepping for Paint
We decided to cover paint prep first because it is 90% of the quality of any paint job. Funny how you will spend 90% of the time on a job just prepping for the other 10%. It’s for this reason, the most important job in a body shop is the preppers. Remember that next time you look down or talk badly about your preppers. They can be a blessing or a curse.
The better job you do on each step, the better your paint will look when finished.
How to Prep a Car for Paint
Updated: Sunday, December 18, 2011
Cleaning before the repair
How can you get a clean paint job in a home made paint booth? Or your home garage? Proper prep is the secret.
90% of the trash (aka nibs) that get into freshly sprayed paint comes from the car itself, not the air quality.
You can get the same or better result at home as you can get with a $50,000 paint booth. The fire marshal may not like it, but the result can be the same.
STEP 1 (clean, clean, clean) Cleaning the Car
A) Clean the car before it enters the work area. This is critical, cleaning the car will remove contaminants. If you don't remove the contaminants outside the work space, as you work on the car, the debris will contaminate it and find its way into your new paint. This is particularly important for commercial body shops as they work on many cars at a time and over many years.
B) There are many cleaners on the market for washing cars, but we have found the most effective and economical solution is “Dawn™ dish soap. It also works as a dust down material but we will add that information at a later date. Dawn has very good wax/grease removal qualities and is sometimes used as a degreaser under the hood and in the engine compartment. You can try others as we did, but you will come back to dawn. Wash as you would normally wash any car, rinsing thoroughly to remove debris. Open the hood, doors and lift gate/trunk and wipe the inside of these areas with the soap towel or sponge. Rinse the entire car again.
C) Check the inner fenders (can be seen after opening the doors), for dirt, leafs or in NC, pine straw seems to be a big problem. Any debris you leave on the car before painting, WILL find it’s way into your new paint, guaranteed. Through the repair process, you will clean the car several times, depending on the amount of work involved.
STEP 2 (Scuff) Scuffing
A) The scuffing process consist of lightly scratching the surface to be painted creating a mechanical bond. Typically a scuff pad (Scotch-Brite) is used with a paste to enhance it’s efficiency. Scuff pads with paste will allow you to get areas you normally would not be able to get to by hand or with a power sander (DA). Scuff pads have different grits just like sand paper but they use color to identify the differences; Red (course) Gray (lighter scratches), as a rule; Reds are used to scuff allover or entire panels that will be painted, Grays are normally used for blend panels as the scratches are not as deep. Deep scratches with the red pad will show with metallic's on a blend. Blend panels typically do not use much base color and will not cover well. We will explain why some scratches show in blend panels and other don’t in a separate part of our website (bookmark). You have a choice to scuff the panels wet or dry. Most people scuff wet as the water will help the debris run of the surface. Because you are in the washing step anyway, it will save time to begin the scuffing process after cleaning while the car is still wet.
- Protect the moldings by outlining them with masking tape (figure 1). If you have to, towel dry the moldings so the tape will stick. This is an important step to protect them during the process.
- Apply the scuffing paste to the panel in a few spots, wet the scuff pad and scrub the entire panel like your deep cleaning (figure 2). Suds will help.
- Work the entire panel carefully to make sure you touch everything, after you wet the pad and begin scrubbing it will be difficult to seen the surface. Keep in mind you must touch every area of the surface in order to lightly scratch (scuff).
- After scuffing the entire panel, rinse with water hose or sprayer completely before moving on to the next panel. Any paste left behind will turn into a powder when dry and find its way into your new paint. MAKE SURE YOU RINSE EACH PANEL thoroughly after scuffing. Use your hand and water to remove paste. DO NOT WAIT until you've scuff the entire car to go back and rinse. When the paste turns to powder it will not be easy to remove.
- Repeat this process on each panel until you have scuffed all the panel to be painted. Keep in mind; if you have blend panels, use the gray pad. When painting and entire panel (base coat), use the red pad. This rule only applies to metallic colors, Solid colors will not show scratches either way.
- After scuffing, rinse and move to the drying process.
STEP 3 (Drying) Drying the Car
A) Pull the car in, open the doors, trunk and hood again. If you have a air compressor, working from the top down, blow off the roof, jambs and inner fenders to remove the puddles of water, wipe with towel if you plan on masking the same day, allow to drip dry if you can leave it overnight. Also blow around ALL moldings, headlamps, tail lamps etc. Anywhere water collects. If you think your masking tape will keep the water away from your paint, you would only be kidding yourself. Your spray gun will put out 25 to 50 psi and that will bring the water out while you paint and ruin the finish. Use a dry towel to dry the bulk of the moisture. Chamois and California Blades work also.
STEP 3 (clean, clean, clean) Chemical Washing
A) Chemical washing is a critical part of surface cleaning and technical in nature. Just because we use the word “washing”, doesn't mean you can substitute this chemical for a household cleaner. Bite the bullet and get some “Wax and Grease Remover” or “Surface Cleaner” from the auto paint supplier store. Its also important to understand how it works to understand why you need to do it this way. There are also things to avoid that noobs typically do there first time.
B) How it Works: After spraying or wiping the cleaner over an entire panel, let stand a minute. During this time the chemicals in the cleaner are actually penetrating the pores of the surface, brining up the impurities to be wiped away. DO NOT ALLOW THE CHEMICAL TO DRY on the surface before wiping, if you do, all those impurities will now be on the surface and you will have a contaminant problem and will need to reapply. Before the chemical evaporates, wipe the panel with a clean paper towel (Bounty™). Bounty has the best cost vs absorption and lint balance. Tear about 3 sheets at a time, folding the 3 into a small 4 inch square, use one side each panel to wipe away the cleaner holding the contaminants, turn to a clean spot on the towel and use that one after wetting the next panel. Work your way around the entire car. Better to use too many towels then to have to polish the clear to remove blemishes in the paint. Polishing take about 15 labor hours, a roll of paper towels is 1.50, you do the math. Clean the jambs, windows, moldings etc. The cleaner the surfaces the cleaner the paint. Be careful to look for trouble areas, places you missed while washing etc. Make sure all surfaces are squeaky clean.
The car is now ready to do whatever repair work needed, keep in mind if all your doing is repairing a fender, this would be over kill but, the same steps can be used on any portion of the car that needs the work.
Summary Steps:
- Clean With Dawn. Jambs, Hatch/Trunk, Under hood.
- Scuff and Rinse
- Dry with compressed air or towels or both (better yet).
- Chemical Wash
- Masking
Tip: The better you do at each step, the better your paint will look when finished. You want a great paint job? Do a great job at prep.
Be sure to bookmark, more coming...
The cleaner the car before you begin work, the cleaner the paint after its applied.
Most of the nibs found in a new paint job come from the car it self.
If wax isn't removed prior to the repair process. It will be pushed deep into the surface, making it more difficult to remove later.
The wax will actually be pushed into your sand paper and spread around the car.
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