How To Prepare Your Car For Painting
Welcome to a comprehensive guide in preparing your car for new paint. Whether you are taking your car all the way to bare metal or painting over existing paint, the following steps are required to ensure a quality finish.
There are two things that are required when prepping your car. The correct tools and huge amounts of patience are required. If you are currently collecting tools as you complete different jobs on your vehicle, spend the time and money purchasing all the tools required to allow you to complete the prep work for paint. If you skip any of the following tools, you will not be able to complete the job to a high level.
Tools required
- Sanding Blocks – Speed files, Rubber Blocks (they have flexibility to contour to your panel).
- Sandpaper – you only need 120/ 150 grit and 600 grit
- Wax and Grease remover
- 2 pack Epoxy Primer
- Guide Coat (Normally dark coloured)
- Spray Bottle
- Plenty of Rags (white is preferable)
- Trestles or panel stands
- Quality Body filler
- Quality Fine filler
- Applicator or Putty knife
- Spare Tile or something to mix your filler on
- Primer Spray gun – 1.4mm Tip is industry standard for Primer
- Air compressor – Bigger the better
- Automotive Tape – Green Tape is normal
- Red Scotchbrite
When you are working on your project, make sure that you have patience. Good bodywork takes time. If you are completing your project yourself, you are most likely interested in saving money by doing it yourself. Poor bodywork means that when you have completed your paintjob and admiring it with a beer in hand that you notice imperfections. After enough time looking at your paintjob, you will be wishing you had spent another half an hour sanding a particular panel.
Manufacturers of vehicles have different standards
When your vehicle was manufactured, flat sheets of steel were put through large metal press and stamped to create the shape of the panel. Repeated process of stamping metal eventually decreases the tolerances of the tooling resulting imperfections to sheet metal. 100% of cars created from sheet metal will have low spots, imperfections and waves. Working on a classic car to restore it or improve it to better than OEM has many different stages that require skill, attention and patience.
You may already have an idea of what colour your car is going to be. Painting your car black means that your body work has to be perfect as it easy to see imperfections. This means a lot more prep time!
Decide what level of finish you are after and stick to it!
You have two choices – going back to bare metal or sanding existing paint. Make sure you have a fair idea of the original paint type the factory used when painting your vehicle. If it is acrylic you may need to use an in between sealer if you are painting it 2pac to make sure the paint does not fry up. If you are not sure what type of paint it is, I would advise going back to bare metal.
If your paint has cracks in it (known as crow’s feet), make sure it has been completely sanded away. In this instance it may be advisable to go back to bare metal. By going back to bare metal you are adding to your workload, however you will know exactly what is under your paint. Beware however, you may find hidden rust lurking under your paint!
If you are sanding your existing paint, use 120 grit sandpaper to remove clear coat. Then scuff the paint under the clear coat. The best way to do this quickly and easily is with an orbital sander (electric or air operated). You must be careful to not burn through the paint creating low spots throughout your car. You can use sanding blocks to sand through the clear coat and scuff the paint however this will take more time. Use the clear coat as your ‘guide coat’. This will tell you what you have sanded and what needs to be sanded.
Going all the way.
Let’s say you decide to sand back to bare metal. The best product to use for this is easily the clean and strip discs mounted to an angle grinder. While each disc is quite expensive, it makes incredibly quick work of stripping panels. You should only require a maximum of 2 – 3 discs when you are stripping your vehicle. Careful when running your disc over the edge of a panel as this is when the clean and strip disc gets damaged and particles break off. Make sure you wear PPE – eyewear and earplugs.
Once your panel is back to bare metal, make sure that your surface is clean and free of any contaminants. Simply pour a little bit of wax and grease remover onto a rag and wipe your panel down. You want to make sure your panel does not have any greasy marks on it. Make sure you use nitrile gloves for this procedure. To dry your panel a little quicker, you can use an air gun to blow the area off.
Once your panel is clean inspect it for any major dents which require panel beating work. If your panel requires minor filler work, buzz your panel with 120 grit sandpaper using an orbital sander. You can also use Red scotchbrite. This will open up the metal to create a good mechanical bond for your filler. Not having a buzzed panel for filler can create delaminating problems down the road. You can also apply filler at a later date. Using 2 pack Epoxy allows you to apply filler on top of the 2 pack Epoxy Primer.
If your panel has slight dents in it mix up your body filler on a board. I normally use a tile because it is a nice hard surface and easy to clean. Apply your body filler neatly using a putty knife.
It's all about the Criss Cross Pattern
Begin sanding your panel in a criss cross pattern. The larger the sanding block, the flatter your panel surface will be. Also remember the harder the block the flatter the surface. Sand your filler until it is smooth with your panel. You will know this by laying your hand flat and running it across the panel.
Get your car ready for primer by taping up parts that you do not want overspray on. The best type of tape to use on panels is green automotive tape. If you are taping up brown paper, newspaper or plastic film, normal masking tape will suffice. Make sure it is stuck properly to avoid any mishaps.
Professionals spray up to three full coats of hifill primer. I highly recommend 2pak Hifill Primer. The purpose of hifill is to build up layers of material for you to sand to create a perfect flat finish. After your hifill has baked or dried over night, it is common for restoration shops to let the car sit for a week or two for the primer to completely harden and cure.
Now that your car is in primer, the work really begins! This is the time that is most important and patience is the key. Painting a car is the fun part, but the preparation is the hardest to get right but is the most rewarding when you have completed the job. You can keep a car in primer for up to 3 years but remember that primer is porous and absorbs water, unlike a painted car which is sealed. Primer can also absorb oil creating oil spots. Be sure to rectify this by cleaning it with wax and grease remover as painting over it will cause you issues with your paintjob in the future.
Patience is the key!
Start with one panel at a time. I repeat, start with one panel at a time. Set yourself a goal. One panel a day!
If the panels are off the car, use a trestle or a panel stand to secure your panel so you can work on it. Work at a height that you find comfortable. Let’s say you start with the boot lid.
You must spray or rub guide coat (usually a dark colour) onto your primer. This is an absolute must to achieve a good finish. Simply sanding your primer thinking that you will be able to keep track of which areas you have sanded and high and low spots is the incorrect way of prepping your car.
There are multiple guide coat products, including in a spray can, mixing some black paint you have lying around or using charcoal rub products. Either way, apply guide coat on top of the primer to the panel that you will be working on.
Using your largest sanding block and 120 – 150 grit sand paper, start in a criss cross pattern eliminating the guide coat revealing the primer underneath. Get into a rhythm sanding 10 times one way and 10 times the other way. Let the block do the work! You don’t need to press to hard. Don’t do a straight pattern – this will make tracks in a panel. It is important to change your sandpaper periodically. It will load up with dust and stop sanding. Sometimes I slap the sandpaper to prevent it from building up.
Slap your Sandpaper. Do it.
Sanding guide coat will reveal high and low spots. Low spots can be rectified using fine filler. If you break through your primer and expose bare metal, you will need to put another coat of primer. This is why many body shop professionals spray multiple layers of hifill to avoid this issue.
Check the progress of your panel using wax and grease remover. Liberally applying wax and grease remover to your panel leaves a shine kind of like clear coat.
Once you have got your panel is straight, I strongly recommend that you bolt your panel back to your car. If you are looking for a high quality finish you will reprime with another coat of hifill primer. Remember: You must reprime if you have applied any type of filler! Painting colour over filler will cause the paint to fry up. Trust me I know from experience!
You have two choices – reapply guide coat and sand at 120 – 150 grit across panels to achieve a seamless finish. You then spray another coat of hi fill primer, reapply guide coat and sand wet or dry for the last time with 600 grit sandpaper. Professionals that charge high prices (Think $20K) for paintjobs will do this additional step.
The second choice if you are pressed for time or impatience is to reapply hi fill and guide coat and sand with 600 grit sandpaper across panels to achieve a seamless finish and skip sanding at 120 – 150 grit for the second time.
600 grit is the correct grit of sandpaper to get your car ready for paint, as you won’t have any scratch marks showing through your paint. You may be able to get away with 400 grit sandpaper, but it’s advisable to stick to 600 grit. Some professional start at 400 grit and work their way up to 800 grit but 600 grit is a happy middle ground. Final sanding with 600 Grit can be done dry or wet. Many professionals sand wet because it keeps the sandpaper clean and lets the block slide over your panel. Keep a spray bottle filled with water and spray it frequently to keep things moving.
You must ensure that the entire guide coat is completely gone and that there are no low or high spots. Once you are confident this is the case this means your car is straight. Congratulations!
Wipe your car down with a rag and then wipe it down with wax and grease remover. Your car is now ready to be painted. All your effort will pay off once you apply the paint to your vehicle.
Join us for the next installment of painting your car.