Back to Archive

With Chris Curwen & Expert Auto Painter - Dave Gage (Car Cosmetics)

August 8th, 2007 - Issue 15

In this issue:

• We continue on the topic of Bodywork Repair and cover Applying Primer.
• Questions & Answers: This week we answer two of our subscribers auto painting related questions.

The first comes from John Szabo and he asks:
 
'Is there a way to safely remove peeling clear coating from undamaged paintwork underneath?'

Our second questions comes from Peter-John and he asks:

'I'm currently buying a XB Falcon ute with a considerable amount of rust. What I want to do is cut it out and replace it with rust repair panels. I can use a mig or a tig but which one would be the preferred welder?

Then after that, I would like to know how to get to the final part of painting, that is the step by step process for stripping and getting the car ready for paint.

I'm going to be leaving the ute in the same color so do I have to rub back the whole ute or can I wash it and then paint straight over the top of the old paint?'

Primer products are used generally on parts of body work that have sustained repair work or have very minor or shallow sheet metal scratches.

Never use primer as a substitute for body filler. Any layers that are applied too thick will shrink making the sanding scratches and other imperfections even more noticeable.

Once you have sanded and smoothed the top coat of glazing putty, apply two to three coats of primer onto the area.

Once dried, smooth the surface with 320-grit sandpaper, then finish sand with 500-grit sandpaper.

Sometimes the multiple coats of primer don't produce the results you were hoping for with minor surface blemishes still showing through.

This is nothing to worry about, simply apply a few more light coats of primer and then sand down with 320- and 500-grit sandpaper once again.

To help you maintain control when sanding primer, spray a light layer of 'guide coat' or matte black paint over the surface. If auto painting is your hobby then you can always apply the 'guide coat' a little heavier compared with that of a professional.

As you are sanding the area down, low spots will stay dark and high spots will lighten as you sand off the 'guide coat' from them.

A substitute for matte black paint would be to use flat-black paint or any contrasting color paint in very light coats.

It is very important that you mask off and protect any area of the vehicle that you won't be painting.

Since primer will be sanded down, you don't need to apply it in a spray painting booth, which makes life a lot easier for you. However, you will still want to use an environment that is as clean and as free of dust as possible.

The amount of solid material in primer remains high enough so that it can flake off masking paper and onto the work surface. For this reason it is vital to remove masking paper that you used when applying primer.

The dust from sanding is going to accumulate on the surface of the vehicle as well as in the gaps between the doors and trunk lids regardless.

This will require a thorough cleaning using an air hose, wax and grease remover and/or an aerosol glass cleaner and definitely a tack cloth before you can apply any coats of color.

Once you have applied and sanded the primer materials and cleaned off any sanding dust from the vehicle, you can then begin the masking process ready for applying sealer and the actual paint.

So how do we successfully apply primer?

Firstly, your aim here is to carefully mix primer to ensure you attain proper coverage from using it.

Try using a calibrated mixing cup to make mixing primer with reducer a lot easier and always make sure you read the instructions before you do any mixing to learn the correct mixing ratios.

Stir the primer mixture thoroughly. Then, place a paint strainer in the spray paint cup and pour in the primer. You should never pour any kind of paint product into a spray paint cup unless you have a strainer in place.

You can get hold of a strainer for free from where you buy your paint products. If you don't use one you risk having to buy a new paint gun if any debris gets into an area of the gun that you can't clean.

Spray the primer onto the vehicle wearing a respirator, remember your personal safety at all times.

It is important that you hold the spray gun at right angles to the surface as you go along, whilst holding the air line in your other hand safely away from the vehicle. Since all vehicle trim should be well out of the way, you will be able to apply a more even coverage.

To witness a professional demonstration of primer being applied to a vehicle, please refer to 'How to Paint a Car - The System' - Part 1.

As you spray the lower edges of the vehicle, it is important that you bend over or kneel down if need be, so you are able to clearly see what you're doing.

Avoid spraying all the way up to the masking paper, this can leave a harsh line in that area. The method is to taper the primer from a heavy application at the actual repair to a thin dusting prior to reaching the mask line.

You will need to apply primer to the inside of all trim openings such as the inside of door handles and petrol cap openings.

It is important therefore that you clean and scuff these areas just as you would do any other area of the vehicle. While this can be meticulous work, the end result will speak for itself.

Questions & Answers

Our first question this week comes from John Szabo and he asks:

'Is there a way to safely remove peeling clear coating from undamaged paintwork underneath?'

The answer to that question John is no, not really. The clear coat binds itself to the undercoat color. Peeling is usually a sign that poor quality materials have been used to paint the car with.

Our second questions comes from Peter-John and he asks:

'I'm currently buying a XB Falcon ute with a considerable amount of rust. What I want to do is cut it out and replace it with rust repair panels. I can use a mig or a tig but which one would be the preferred welder?

Then after that, I would like to know how to get to the final part of painting, that is the step by step process for stripping and getting the car ready for paint.

I'm going to be leaving the ute in the same color so do I have to rub back the whole ute or can I wash it and then paint straight over the top of the old paint?'

Use mig welding to weld in the replacement panels and as for the paint work, wash the car using a strong detergent, DO NOT WASH AND WAX!

(Primer and paint will not stick to dirt, wax, or grease. This is why you will have to take your time to remove all such debris from the surface of the vehicle being repaired using wax and grease remover. This will leave the surface as clean as possible.

You will need to be meticulous in this area. It is important you do this after you wash the vehicle, before you sand it, after you sand it and between undercoats and top coats. Remember that each paint system will come with its own recommended products.)

Then flat the old paintwork using 800-grit wet and dry flatting paper before applying the new paint.

Hope this helps guys!


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.

Next week we'll conclude the series on Bodywork Repair and cover Preparing Fiberglass.

Happy Painting!

Chris Curwen & Dave Gage
www.LearnAutoPainting.com