Here is a "Basics" on the subject.
"Basics of Basics" Paint together or in pieces?
By Brian Martin
One decision that must be made during your cars restoration will be if it should be painted in pieces, with the doors, fenders, trunk lid and hood off the car, or with all the body panels on at once. There are many reasons to do it one way or the other and it should be well thought out prior to laying the paint on.
What is the “best” or the “right” way is very different to most anyone asked. It really depends on your expectations, skills and passions. Do you want the car accurately restored? Do you want the easiest way? Do you want the highest quality result? The “best” is not always the way to accurately restore it. Many times the factory did things that are far from “show quality”. They were simply building a car for the masses, not building a classic. Most ever car built has the doors installed on it when it’s being painted. Yesterday, today and tomorrow, new cars being built have the doors and trunk lids hung on them. In some cases such as sixties GM and Ford cars, not only were the doors and trunk lids installed on them, so were the latches and strikers! Yep, they painted right over the latches, strikers and the bolts that held them on many cars made in those days. This is the practice with many manufacturers up to today with strikers, they do usually leave the latches out though. That is certainly not very “show quality”. Some cars in those days had their front fenders, hood and cowl top (if it used one) painted on a rack out in front of the cars body. I started in the autobody and paint industry in the 1970s and I have to tell you, it was common to see a GM car where the fenders didn’t match the doors because of this practice of painting the body/doors and fenders and hood separate. These were single stage lacquers and a little difference in distance or pressure could change a metallic color pretty fast. There were sometimes bare spots under the lip of a trunk or the bottom of the door inner jamb (especially in the corner up at the hinge area) where the paint and primer was very thin and there would be a minor rust forming when the car was still only a year or two old. So, this is “correct” for restoring many cars, but it certainly isn’t the “best” way to do it.
Most cars today are painted in an interesting way. They are painted with robots, some are painted in a “shower” like booth. It is actually kinda freeky to see them painted. They sort of just “change color” like a computer special effect. They are painted with the doors, trunks, hoods all on as they always have been. But now often they will shoot a base that is similar to the final color. Then they shut the hood (and sometimes the trunk) and paint the outside of the car and door jambs with the final color and clear it. Under the hood, and the trunk in many cases gets no clear or final color! And to throw another odd trivia bit out there, this is interesting. Toyota, probably the most effective manufacturing company in the world paints their cars this way. But after painting the car they remove the doors, for the cars component assemblies to be installed and then the doors are reinstalled as one of the very last steps! Now, if Toyota and all their amazing manufacturing processes do this to ensure that all the parts are the same color, I think it is safe to say painting the car together is a good idea.
Have you ever looked close at the cars you see at shows? Do you see the ones that are painted apart (or at least look like they were) compared to the ones painted together? Do you know the difference? Most of us check out these cars and never even look close enough to see if they are that well detailed. Only you know for sure if you want nothing but the best and are willing to spend the extra time to paint it apart, then do it. If you have seen at shows that cars look good to you even if they have those small tape lines in the jambs, then painting it together may be the way to go.
The benefits to painting it in pieces are there, first off, a super detail job. You can spend all the time you want prepping all those nooks and crannies for a super nice paint job. No tape lines, it just looks awesome, however is it practical for you and your car? Bolting newly painted parts on is pretty taxing. If you do go this route, be sure everything fits first. Read my “Basic of Basics” on trial fitting parts. It is very important that all these parts fit if you are going to paint them off the car. If you have any doubt, any doubt at all, paint it together. I have seen many, many cars where the guy thought the parts fit, he was certain that the parts fit. After the car was painted he had very poor fitting panels when installed. I don’t care if they are NOS, I don’t care if they fit well before the body work on the adjacent panel was done, what ever, you must trial fit them. If you are going to toss the dice and you lose, you lose big. If you want to save the time of trial fitting, just bolt it together and paint it that way.
First, do you have room to shoot it in pieces? Now, this can be a great way to shoot something when you don’t have the room as well, depending on if you are shooting it all at once or in pieces over days or weeks. If you feel that you can paint it in pieces (IF you can will be covered later) this can work out great. You paint your fenders, then put them away somewhere and paint the doors and so on until the car is done. If you plan on painting it all at once while in pieces, than you better have a big booth to spread it all out.
Painting cars in pieces can be a little easier in that you have a number of small projects that are easier to handle. Painting a complete can be overwhelming to a newbe, the many smaller steps make it more manageable. But you must be sure that you are not learning on your car. If you start painting parts as “practice” you will most certainly not be painting the same by the time you get to the last pieces, and they will likely look different. If you have some help putting it together it is not that difficult to do with it painted. It just takes care, lots of it.
If you do paint it in pieces, you must have the parts (especially with a metallic, but with solids colors as well, more on this later) hanging in the same “attitude” as it is on the car. In other words, you don’t lay the doors down on their back to paint them. You want them hanging vertically just as they are on the car.
When you spray them, you need to maintain the exact same distance, pressure, surface/shop temp, solvent temp, amount of coats, reduction, etc. This is very important, the consistency is key when painting a car apart. When spraying a panel off the car you want to “pretend” that the next panel is there and take each pass well off the panel you are painting onto this imaginary panel. This will keep you from stopping right at the end of the panel and creating more or less (depending on exactly your trigger technique) film build at the end than in the middle. This can create a different color in those areas. Metallic colors being different because of air pressure is a given, most understand that. But solid colors can change with a little varying of distance and pressure as well. It is simply because of film build. Today’s lead free paints don’t cover nearly as well as years ago. Where you think a few coats have covered, it may not have. Sure, if you have applied those four coats uniformly over a single color substrate like a completely gray primed door, it is a uniform color. But apply one more coat and you have a different color. Therefore if you don’t run the gun off the panel onto the adjacent imaginary panel, and apply exactly the same amount of coats you could put a little more or less material at the edge creating a different color there. If you do it a little different on the REAL adjacent part, the two won’t match. This is very common on something like the back of the door to the quarter panel. You are painting the quarter totally different because you have the jamb to paint as well. So right at the edge of the quarter you are going to have more material applied being you coat the jamb as well as the quarter with a little overlap at the edge. On the door, you don’t paint it that way because the jamb side is painted from the back. So if you were to stop the gun short right at the edge, you are going to have a little different film build. You could very well have a color that is slightly different from the quarter.
One VERY important thing is that ALL the parts have the exact same primer color. Even colors that cover well are going to have a hard time over a gray primered body and a black urethane bumper! You WILL have different colors when finished. Be sure everthing, including substrate color along with pressure, solvent, distance, etc.
Another very important issue is that you must be sure that you have all the paint you will need. Buy at least 30-50% more than you think, that is my personal target. I want to have a quart or more unreduced paint left over. I’m sorry, when it comes to paint problems, and redos the price of a quart of paint is not a big deal. If you need it, it is priceless. So, buy your paint and get a couple of gallon cans and intermix them. Stir them well, being sure to get everything off the bottom of the can. If you can have the paint store shake them, that’s good too. I like to scrape the bottom of the can with the stir stick and then run the very bottom of the stick on the inner edge of the can and look close to be sure there is not toner on the bottom of the can that isn’t stirred up. Pour the paint back and forth until they are thoroughly intermixed. Let me explain, you have two one-gallon cans, with lets say a gallon and a half of paint, one gallon can full, the other half full. Pour about a quart or so out of the full one into the half full one, then stir it up. Now, pour a quart or so back, then stir that up, do this a few times back and fourth until you are certain to have the cans intermixed. You do this because there may be a slight difference between the two mixes. After all they were mixed by a human being. Now, after using one can you can go to the next knowing they are exactly the same color. If you should run out and go back for another quart, you could find yourself with a much different color! This is a very hard learned lesson, avoid it, simply buy enough and intermix it right from the start. This practice should always be followed, be it painting the car in pieces or not. But it is particularly important if you are.
Another alternative is to do both, paint it together but like the factory with the doors and trunk and maybe even the hood hung. Again, there are lots of choices. Many cars were painted with the hoods hung, hinges and all got painted, you could do the same. I have never actually done this, but seen many painters do so. They open and close the panels (leaving the latches out so they swing freely) with every coat. Painting inside and outside at the same time. You need a lot of room to pull this off, but it can be done.
You can also do things like bolting parts on like fender extensions with washers behind them to space them out so paint gets behind them. This is a favorite trick of mine. That way you jamb behind the extension first, then with it spaced out a quarter inch or so, it gets painted just like it was bolted on. Works like a charm even with a metallic color. The washers are removed after the painting is complete and the extension is bolted on properly.
Now, painting it together, what are the benefits? Well first off, you know the parts fit. You know that it all works and after unmasking you are going to have a nice fun time bolting on all the chrome and trim. Half the work is already done, you are home free. You will have some tape lines, it may not be the ultimate show car, but it still can be darn nice.
One thing to do when painting the jambs first and the body complete is to be sure that all the body work and priming is done before you do the jambs. There is nothing that will send the quality of your work going down the drain faster than painting the jambs and then having to apply primer on the panels and mess build up more of a line, get overspray on the jambs, etc. Do all the blocking, all the priming, all the panel and trim fitting before you paint the jambs.
When painting the jambs, mask off the surrounding outer panel. Don’t let the overspray fall out onto the panel thinking you are going to be sanding it anyway, what is the harm? There are a number of reasons why you don’t want to do this. First, you want the body do have a uniform substrate color. Second, it will take a lot of sanding to feather this out and you can damage the blocking you did to get the body straight. Third, if you don’t feather it out completely you have a very thin film there at the edge of the overspray where solvents when you paint the outside can get under and lift it. To avoid a lot of problems, just don’t let the overspray out onto the outside. Mask it right up almost to the corner of the outer panel, leave about a sixteenth inch of primer around the corner into the jamb.
After painting and assembling the panels back on the car, when you are sanding the car for paint, pay close attention to those edges of the paint in the jambs at the primer on the outside. For detailed tips on this read the “Basics of Basics” on taping jambs. Basically, you want to carefully sand those edges away. Mask the jambs off by back taping to allow the paint to fall over the edge onto the painted jamb about an eighth inch or so. That means that only about a sixteenth inch or so of the paint in the jamb is exposed when masked. That little edge can be sanded and buffed out leaving an almost invisible seam.
To the guy who wants to make his car as flawless as humanly possible and paints his car apart to the guy who paints it together and gets out on the road with a smile on his face driving it, you have my respect. It is your car after all, make the decision with as much information you can get on the subject. Don’t take it lightly, it is an important decision to make on the restoration of your car.
And last but most certainly least, One VERY important thing is that ALL the parts have the exact same primer color. Even colors that cover well are going to have a hard time over multiple color primered parts. You WILL have different colors when finished. Be sure everthing, including substrate color along with pressure, solvent, distance, etc.
So either have the every single part primed in the same color, ready to paint. Or, seal the every single part in the same sealer before printing. But you must have all parts the same color prior to painting. Even when applying many coats, it would blow you away how much the substrate color (the color you are painting on top of) can change the final color. You don’t want to “ask the paint to do to much”. If you have all the panels the same color prior to painting, you have a MUCH better change that all the panels will be the same color when you are through.