Introduction: Hobby Auto Restoration: Primer and Sanding
A few years ago, my family and I restored a 1976 Camaro. We started with a rusty, dented 76 body, bought out of a junkyard with a running motor for two hundred dollars. From there, we replaced the original front clip with a 1970 1/2 Rally Sport front and also welded on a 1973 tail end. If you are unfamiliar with this ear of Camaro, 1970 1/2 through 1973 are almost identical. Other than the front and rear, the rest of the body did not change much from those three years to the 1976 either. In the end, the restoration was completed for about $3,200, much of this applied towards paint and painting supplies. I would like to be clear that this car is not restored to show quality; we use it as a daily driver. As our first projects with body restoration, we developed some useful methods that will be outlined in this Instructable.
The project taught us there are endless ways to approach classic car body restoration. I will detail the processes used on this 1976 Camaro. I strongly encourage gaining as much other information as possible to form your own ideas as well. This Instructable enters the process after the welding of patch panels and application of body filler.
Step 1: Supplies and Saftey Issues
Supplies - These can be found at many auto part shops, tool stores, or home improvement stores
- 17" wooden sanding board
- Rubber sanding blocks (3M brand shown)
- Wet/Dry sanding pads (3M brand shown)
- Kitchen sponges
- Rubber squeegee
- Bucket
- Sandpaper - 150, 220, 320, 400, 500, 600 grit
- Face mask
Note: Primer and mixing supplies listed in Step 2.
Safety Precautions:
As always when working with tools, general shop safety must be practiced. Mixing and applying paint and primer requires extra caution to ensure proper ventilation of the work space. We commonly used box fans to circulate fresh air. In addition, you must wear the face mask when spraying paint/primer to prevent ingestion of dangerous fumes.
Step 2: Mixing Primer
Primer Supplies:
- Sandable Primer - Valspar 96N*
- Sandable Primer Activator - for Valspar 96N*
- Thinner
- Clean soup cans
- Paint stirrers**
- Paint filters**
- Gravity Paint Spray Gun
- Air compressor
* We chose Valspar brand due to its hard-drying properties. It sanded off slower, allowing more room for mistakes and learning. However, Valspar is very expensive.
** Both paint stirrers and filters are usually included for free when you purchase paint or primer, but you may need to ask for them specifically.
Steps:
1. Thoroughly clean a container to mix the paint in. We used large soup cans.
2. Make sure that the bowl of the paint gun is free of previous paint, dust, or other debris. Pour
some thinner in the bowl to clean, then spray some through the nozzle of the gun, wiping off the
face.
3. Refer to the proportions listed on the labels to determine the correct mixing ratio of paint and
activator. These values will differ between types or brands.
4. Add thinner to allow the mixture to pass through the gun nozzle and lay smoothly.
Note: the amount of thinner added may change depending on the kind of coat you want to
produce. For example, the first layer of primer should be thick, so use a one-to-one
ratio (equal parts thinner and paint/activator mixture).
5. Pour the desired amounts of each into the can and stir thoroughly with the paint stick.
6. Pour the paint mixture through the filter and into the bowl of the paint gun.
Step 3: Sealant Coat
Mix a batch of sealant, in this case black epoxy primer, as seen below. This will trap all contaminates, such as oil, from affecting the primer and paint. Spray it on the vehicle in two or three coats.
Note: From this point on, any type of oil, grease, or other general contaminates must be kept
free from the car's body. They will cause reactions in the paint such as orange peel, which
has a rippling effect. Take special care of rags and tools, and keep your hands clean.
Scuff the entire body with 150 grit sandpaper. Scuffing is sanding lightly to ensure that the primer will stick to the surface. You can do this either by hand with blocks or with a DA (dual action sander).
Step 4: First Layer of Primer and Basic Sanding
Next, mix a batch of sandable primer. Sandable primer is meant to fill in imperfections and allow you to take any waviness out of the body. For this layer, a heavy coat of primer should be applied to the entire body. Do not worry if runs form, focus on creating a solid base coat to blend in body filler and remove dents and waves.
Sanding steps:
1. To start, wrap the 17" wooden sanding board with 150 grit sandpaper.
2. Sand the body in an elongated X-pattern as shown in the second photo. This allows you to
follow the contours of the body. Sanding only in parallel horizontal lines can cause a chunky
effect, sort of like window blinds.
3. Overlap the X-patterns, as shown in the third photo.
4. Finish each section with straight strokes following the body lines (the last picture).
Note: Areas such as the front and rear of the car are too small for this large board and
X-pattern. Here, wrap sandpaper around any of the other blocks or use your hands, still
following the original contours.
Basic Sanding Methods:
- Always remain aware of the body lines of the car. Generally, sand in strokes from the front to the
rear of the car. On the door, for example, do not run the sandpaper vertically.
- Use the full extension of your arm for sanding strokes. These should match the longest
possible lines on the panel.
- Let the sandpaper do the work for you. Apply only light pressure to the board. Excess force
causes uneven sanding and deep scratches.
- Keep continuous with your movement, not dwelling on one stroke.
- Primer will be removed from edges and body lines more quickly than flat surfaces. For
example, sanding through the primer occurs quickly in places such as around the headlights or
down the main creased body line.
Step 5: Problem Areas and Second Coat
Focusing on dents and body filler areas:
- Low spots in the primer can sometimes be identified by sight, as in the picture below. Other
times, watch for spots where you can tell your sandpaper is not reaching the surface. Scratches
may follow a different path than you are sanding, or previous, deeper scratches may be visible.
- Many times, the eye alone cannot completely identify a dent or wave. We found it very effective to
physically feel for them with our hands. Use your non-dominant, more sensitive hand, and look
away from the area in question. This removes what your eyes see (or think they see) from the
equation.
- If you find a low area, sand the surrounding primer down until they meet, and vise versa for high
spots.
- While sanding, work towards a mirror like finished product, and this will give you an intuitive
idea of the coreect processes
- Keep in mind that you may need to repeat some of these steps multiple times. Also, if you find
difficulty with a certain area, feel free to spray only that spot with additional primer and sand
again.
With most major problems removed, spray a light coat of primer. When mixing this coat, add much more thinner than before. This will not create much build up, but it should fill in large scratches left by previous steps. This way, you can save time sanding these out and work towards finish sanding. Proceed with the same sanding process with 220 and 320 grit sandpaper.
Step 6: Wet Sanding Processes
Wet sanding (using water with fine grit sandpaper) keeps both the paper and surface free of dust that accumulates from sanding. During this step, the surface and paper must always remain wet.
1. Fill a bucket with water.
2. Wrap the flexible wet/dry pad in 400 grit sandpaper.
3. Dip both the block and paper into the bucket. You should squeeze water on the area you will
be sanding with the sponge.
4. Sand the entire car in the longest possible strokes, following the same process as outlined in
Step 4 (replacing the large wooden block with your wet/dry pad).
5. The rubber squeegee can be used to clear the body of residue to view our work.
6. Make your way round the vehicle again using 500 and 600 grit sandpaper. We noticed with
these finer grits, the primer started to show a little shine. This reflection helped us check for
straightness.
If sanding with a flexible pad or simply your hands, keep your fingers perpendicular to the sanding motion. If they are parallel, ridges form matching your fingers. Try to think of your hand as if it were a block. Do not press with excess force on any one finger or finger tip.
Note: No single step of the sanding process will remove every dent, wave, or imperfection. It
is imperative during each step to actively look for and sand out these problems, even if it
means backtracking.
Step 7: Color Sanding
At this point, you could go ahead and paint. We chose to "color sand" the car, or spray a layer of the base coat paint and wet sand once more.
1. Wipe or spray all dust particles and residue off the car.
2. Mix a small batch of the base coat color, and spray on to completely cover the primer.
3. Once dry, wet sand the entire body as described in Step 6 with 600 grit sandpaper only.
You can easily identify high or low spots due to the sharp contrast between the paint and primer. Feel free to go all the way through this color coat if necessart to remove these spots. Do not sand to quickly, take your time as this is the final step of preparation.
Step 8: Finishing the Project
Once you are happy with the straightness of the car, you have finally finished the sanding process. To clean the body, wipe it off with clean, dry rags to remove all dust, and it is ready for paint!
Even if you are not painting the car yourself, completing the prep work can save a lot of money at a restoration shop and is a great way to spend time with family or friends. Overall, patience and perseverance are key with any auto restoration, especially body work.
Good luck with your projects!
