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................- Bodywork & Painting Page 2 -
........................................................- Priming -
Paint can be a real personal thing, so bearing that in mind I'll tell you what I use and why and also how I put it on, but these step can be done different ways with different products and still achieve good results.
.....................................- PPG DPLF40 Primer -
I coat all of my bare metal and bondo areas with PPG's DPLF40.
Note: The number at the end denotes the color as this comes in a number of different colors. If you are going to be using a light final color you could use a light color here. Not so important at this stage, but the DP can also be mixed as a sealer and you want your sealer to be close to your final color so you don't have to use as much base color to hide the sealer. Also I used DP on my truck and it is now been replace with the DPLF (LF standing for Lead Free). Only time will tell if it is as good as the DP that came before it.
I am not sure of the other paint suppliers having a product quite like the DP and would like to know if they do. It is very corrosion resistant and bonds very well to bare sanded metal and bondo. It is an excellent foundation between the metal and high build primers. It is a non sanding primer though that is not meant to fill and has to be top coated within one week with another primer or other compatible top coats. The reason for this is that paint bonds to a surface through either a mechanical bond (the need for the fine sand scratches) or a chemical bond (epoxy) and this paint does both, but since you don't sand it the paints on top of it have to be applied within a week for the chemical bond to take place since there isn't a mechanical bond between them and the DP. This is the reason I don't put it on and then bondo over it, since working as a hobbyist I might not get the bondo done and the whole works topcoated within a week. So I do the bondo work and then shoot the DP followed by the K36 in the appropriate time.
This combination has worked great for me and with over 110,000 miles on my GMC it has not failed in any way and I've been on the salt flats with it for over 35 days and this is an excellent test plus I've put on many miles in the rain and snow. If I lived in the rust belt and had a car I wanted to keep I would for sure use it.
A note here about etch primers. Personally I don't use etch primers. I feel the DP is superior for my projects as it provides an excellent bond and also protects the body from corrosion (read rust). I've noticed that a lot of times the rock chips I get in the paint go down to the K36 primer or the DP primer, but hardly ever to the bare metal. So if I get a chip down to the DP level it still isn't going to rust. Etch primers are cheaper and have their place. That place I believe is in production work. Now you don't want to use both, so decide if it is going to be DP or etch, but I would use one or the other for the first coats on the bare metal unless you are using a system that has something else.
I first blow off the bare metal and the repaired (bondo) areas to be painted with my air nozzel. Next I clean it with PPG's wax and grease remover #330.
Next I spray the panel with 2 coats of the DP (mixed as per instructions). You can use 1, but I prefer the 2 to make sure of my coverage and paint thickness. One other thing is the DP can be kept for a while after it is mixed. I've kept it a few days in the frig and it was still good. Read the instructions and don't forget after it is mixed you have to wait 15 to 30 min. (depending on the activator you use) before you can spray it.
Paint Mixing Tip: Here is something I learned from a painter friend a couple of years ago and now use all the time. You can mix paint in all kinds of ways, but I've found that the most accurate, simplest and easiest for me is the following. I bought the glass Pyrex mixing bowels (the clear glass with handles and graduation marks on the side) in 4 sizes going from their smallest on up.
You mix your paints in ratios, for example 4:1:1, which might be 4 parts primer to 1 part reducer to 1 part hardener (this is only an example). So if I wanted to spray a small part I would fill the small mixing bowel up to the 4 oz mark, then pour the reducer in to the 5 oz mark and the hardener in to the 6 oz mark. This would give me the 4:1:1 ratio.
Say I'm going to paint something larger like a panel. I would get a larger bowel out and fill it to the 16 oz mark (4 parts) with primer. Then I would add fill to the 20 oz mark (1 part--4 oz) with reducer. Finally I would fill to the 24 oz mark (1 part--4 oz) with the hardener.
It is simple just keep the ratios the same.
It is then easy to pour from these containers through a strainer into your gun. I clean the gun parts in them and they are easy to wipe clean with a paper towel and paint thinner. Keep them and you gun cleaned spotless every time you use them and your gun will keep working for you the same way.
..............................................- PPG K-36 Primer -
Note: the K-36 is a high build primer designed to fill low spots and sand scratches from body work. It will be sanded and then top coated. I used K-200 for the primer on my pickup, but even though it is a 2 part primer it IS NOT WATERPROOF. I didn't have any problems in the years I ran around in primer because the DP40 was under it and provided the moisture barrier. K-36 is a superior product to K-200 and it is waterproof, so it is a better product than the older K-200. It also sands super.
After spraying the DPLF40 I will wait the appropriate time (but not over a week) and then spray on 3 wet coats of K-36 mixed as the normal build. I'll usually do this the same day or the next.
Before spraying the K-36 over the DP I first blow the area to be painted off with my air. Next I clean it with PPG's wax and grease remover #330.
The purpose of the K-36 is go give you some paint thickness so you can sand it down to fix minor imperfections on the surface. Think of it as your tool to fill the low spots that are left at this stage. If you do your body work before this stage good you don't need to mix this in it's high build form ( I always mix it in the normat regular build vs. the high build ratios). If you do mix it in the high build form, don't forget your spray gun might need a bigger tip to allow the material to pass through.
Also this stuff hardens fast so don't mix more than you can use in the next 60 minutes (see it's instructions) or it will harden in the gun. Clean the gun immediately after spraying and follow the directions for flash time between coats.
After the K-36 has dried, preferably overnight, you will block sand. Spray on a guide coat first (as mentioned earlier). Next I sand with 180 grit dry or 220 grit. USE YOUR COTTON GLOVES TO KEEP OIL FROM YOUR HANDS OFF THE PAINTED SURFACE. Different people use different grits in the steps I mention here, but there again this works for me.
Use your different sanding boards and blocks for this step. Use the longest board that will work in the area you are doing. This is the most important step to a great paint job, so do it right and don't rush it. I buy the 180 in a roll and then tear it to length for the block or board I'm using it on. In this form it has an adhesive back and works a lot better than sheets of sand paper, but you can do that also. Change you sand paper as soon as it stops cutting. Don't push it or you will start wallowing out spots. Knock your paper often to remove sanding dust from it and wear a mask.
Remember you are sanding, but really you are cutting off the high spots down and removing the 80 grit sand scratches. Sand in your X pattern and constantly move the area of the X around and do the X from different angles on flat areas. Do the curves like before, by sanding over the curve in an X pattern and not along it. You sand until all the guide coat is gone. If you see an area where you start to sand into the DPL40, but next to it you can still see guide coat then the guide coat area is low.
Now it is decision time. If if is so low that you can almost sand it flat then the next coats of primer might fix it. Don't sand into the DP. It is okay at this point if you barely sand into the DP, but don't sand to bare metal.
The exception to this is if you really screwed up earlier and you have a definite high spot that needs to be knocked down. If so take your hammer and dolly and gently knock it down. If you do this and/or you have a definite low spot this area is going to probably need more bondo. I say bondo, but the stuff you used on the bare metal is not the best for this stage. Get a type that is meant for this. Make sure it is 2 part and not the old stuff in the tube. Buy it the same time you get your main bondo. Dupont's name is Final Fil. These products are made to go over primer and they sand extremely well. If you use it at this step (it can also be used in your panel repair steps) be sure to sand it with 180.
Now spray on 3 more coats of K-36 over any of these repaired or low spots. Before spraying again blow the area to be painted off with air and clean it with PPG's wax and grease remover #330.
Next guide coat the area and sand it with the 180.
When everything has been sanded flat (no more guide coat showing) with the 180 then shoot on 3 more wet coats of the K-36. Before spraying again blow the area to be painted off with air and clean it with PPG's wax and grease remover #330.
I sand these coats of paint flat with 400 wet sandpaper (here again some will then go to 500 or 600, but the 400 has worked with the sealer, base and clear I've used). This paper I get in sheets.
Get a bucket of clean water and squirt some dishwashing detergent into it (just one squirt). Get a large sponge. Put about 3-4 sheets of the 400 sandpaper in the water. You want them wet and soft. Put on some latex gloves or you will sand your finger prints away ;-).
Get a good stir stick that is thick and straight. Wrap one of the sheets of the wet sandpaper around the stir stick over and over until it is all wrapped around the stir stick. This will be your sanding block for most areas. For sharp curves use a hard rubber sanding block and for real tight curves use a softer one.
Guide coat the panel next. Now put some water on the panel with the sponge and sand in the same manner as before (moving X patterns). Try to keep the sponge with water on it above the area you are sanding. Keep dipping the sand paper into the water to clean it and keep water on the sanded area to remove the sanding residue you are creating. You can use two hands on the stick, but stop often to rinse the area with water. This actually goes pretty quick. As soon as the paper is not cutting tear off the paper down the length of the stick and the width of the stick. Since the paper is wrapped around the stick you keep having new paper each time you tear it down the stick until it is all gone.
During this step we need to keep the flatness achieved in the preceding step when we sanded with the 180 grit (that is why it was so important to get the final flatness during that step). Our main objective is to sand the primer down until the we get rid of the 180 sand scratches and to provide a very flat smooth finish for the sealer, base and clear. Sand until the guide coat is gone. You will see there is also orange peel created when we spray on the primer. This has to be sanded flat and the guide coat will help you here.
It is also possible to still find low areas. If so this is your last chance to fix them. If they are there then do what you have to to fix them now, but be sure once they are fixed they have been sanded down with the 400.
Note: Long flat areas like hoods, doors, and sides are going to really show if they are not flat. Wet the primer and get some lights on them so you can look down them and make sure they look good with no waves or ripples. Curves, such as fenders, are going to be more forgiving and small curved areas, such as jambs, and window moldings are going to be the most forgiving if they are not perfect. I spent too much time on some of the small curved areas and didn't need to, but it is better to error on too much attention to detail. After this stage what will happen is that when you put on the clear it will highlight the bad areas not cover them up. They won't go away. Not to scare you too much, but get it right before you go to the next step. The guide coats won't lie to you. If you sand things flat and don't go into an area and just sand the guide coat away (wallow out the area) you will be fine and you'll have a great paint job. Everyone asks who painted the car, but it is these steps that make a great paint job, not the painting of the base and clear.
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