For hand sanding i start at the top and work my way down, usually 3 or 4 passes on a panel. for large flat areas like the hood one pass is enough. after i am finished with a panel of car, i use an electric hand sander to take off any residual sanding marks from small curves and contours under the windows. it only takes a few seconds per panel. if you are doing several vehicles in back-to-back fashion then you may want to clean your ego pad after each vehicle before starting another one because even water will have some negative effect on its performance over time if it is constantly being used without ever being cleaned out.”
how to sand a car by hand
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what grit sandpaper should you use to prepare a car for paint?
you want to use a 240-grit sandpaper for this.
it is very important that you prepare the car properly before putting on paint, which means sanding off the old clear coat that is on there with course-grit sandpaper (around 100-grit) until you get down to bare metal. next, you use the 240 grit sandpaper to scour away all of these scratches. this removes any fine scratches or pitting in the metal…you'll notice i said “scour”. that word doesn't get used enough in describing paint prep. it does more than make it smooth; it cuts through oils and residue, giving your surface cleaner access to start bonding with primer and/or paint!
do you have to sand a car before painting?
yes, because sanding removes the existing paint and leaves a clean surface for the new paint to stick to. by doing this you can ensure that your car won't fade as quickly and will hold color better. the reason people often ask if they need to sand before painting is that they see pictures of cars that have been painted with uneven or lumpy surfaces and wonder if this is what'll happen to their vehicle after having it professionally painted. help assure them by letting them know about how much work goes into creating a perfectly smooth surface on their cars before we finish with applying our paint coatings so only high quality craftsmanship will result in an evenly painted car.
preparation precedes painting! most people don't
how long does it take to sand a car for paint?
this is something that can vary greatly depending on the type of car, the buffer system you are using, and many other things. generally speaking though, it's safe to say it will take anywhere from five to seven hours per coat (depending on your technique). this means if you want to complete an automotive paint project in one day, you'll need about 30-36 hours in total.
can you paint over existing auto paint?
it's possible to paint over existing auto paint. however, the old auto paint will show through, so there are some limitations on which type of new paints can be applied. for example, it would not be possible to cover black with purple. the old electrocoat is usually stripped away before any new paint job begins; otherwise the new coat may eat into or peel off of the original surface below it. typically that removal process is accomplished with chemical strippers like methylene dichloride (which attacks oils), acetone (for plastic) and hydrogen peroxide (for rust). a heavy duty pressure washer may also do the job for rough surfaces if undercoating isn't present or fails to adhere properly.
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