Painting a Classic Car with Cellulose
Firstly, I should say that I am no expert on painting; however, I have resprayed a number of classic cars at home myself and achieved excellent results.
This article is an edited version taken from my Citroen DS Restoration website. This page is intended to give a little insight into my experiences and to help other DIY painters along.
A word about equipment. You're going to need a few obvious things to paint a car :
- A compressor
- At least one spray gun
The choice of compressor is very important. You want something big enough to power a pro spraygun, and something that isn't going to be cutting in every few seconds. My compressor will supply 14cfm (10cfm FAD) of air, which is plenty for almost any air tool around. If you're looking to buy a compressor, look for 14cfm. The 8cfm ones are alright for filling tyres, but it won't power a top spraygun. A big tank is good too, so buy the biggest you can. The secondhand market is a very goodplace to get compressors; I got mine from eBay for £200; new it would have been over £600. It had been well looked after (under a service contract from Ingersoll), so I wasn't worried.
A mistake a lot of people make when painting a car for the first time is to use a cheap gun. As an experiment I painted one panel with a cheap (i.e. around £10) gun, then painted another with a pro gun (around £180). The finish from the pro gun was almost perfect, the finish from the cheap gun was crap. Basically what I'm saying is buy the best gun you can afford. Again, I picked mine up second hand; the gun I use is a DeVilbiss JGA, which is the 'industry standard' amongst pros. They are around £180 from Machine Mart in the UK but it's well worth it. Bear in mind that a pro gun will use a lot of air, so you need to make sure your compressor will keep up.
Preparation is everything. No two ways about it, you'll spend most of your time preparing the panels. Here are the steps I took in preparing the rear wing of a Citroen DS:
- Remove all old paint if unsure about metal underneath. Otherwise flat old paint.
- Use filler to correct any low spots in the panel. You may need to repeat this step a numer of times to get the panel flat.
- Sand the entire panel with 400grit sandpaper until all old paint is feathered and filler is perfectly flat.
- Apply a coat of etch primer to any bare metal; this is a special primer which will burn itself into the metal and ensure that the paint sticks to it.
- Apply 2-3 coats of Primer Filler. This is a high-build primer which will help hide any smaller imperfections.
- Flat primer filler with 600grit paper. Apply more coats as necessary.
- Examine panel and use stopper on any tiny imperfections, e.g scratches or chips. Stopper is a product similar to filler, except that it is much smoother and easier to sand. Look for the 1K stopper, which comes in a tube and doesn't need hardenener; it's much easier to use!
- Flat all stopper and apply a futher coat of primer (normal primer would do here)
- Flat the panel with 800 grit paper, this will give a perfectly smooth surface for painting
- Apply a guide coat. This is a very thin coat of dark paint, usually you would use an aerosol of dark blue for this. (Black takes longer to sand apparently)
- Flat the guide coat back, this will reveal any imperfections you missed in the earlier stages. Repeat above steps until panel is perfect
- You're ready for painting!
Here's the rear wing after having stopper applied. Each little white patch is where there was a tiny imperfection.
The DS Rear Wing With Stopper Applied
Your panel should now be ready for painting, but before you do anything you need to use a combination of a blowgun, tack rags and spirit wipe to remove any dust or silicon from the panel. You can buy all of these things from a paint shop. You need to go over the entire panel with the tack rag and spirit wipe, and blow out any crevices with the blow gun. You'll know if you get silicon on your panel, the paint will fish-eye and you'll have to start again...
Paint - the only paint that is suitable for home-use is Cellulose. Don't even think about using 2-pack paint at home unless you want to commit suicide, you need specialist breathing gear to spray 2K. Cellulose is a little harder to find than 2K, but look in the Yellow Pages under 'Cellulose Enamel and Lacquer' and you should find somewhere that sells it. I've paid between £12 and £16 a litre for cellulose in the past. For a medium (such as my Citroen DS) sized car you'll need about 4 litres of paint. If you buy more, you'll have plenty left to touch up and believe me you'll be glad you bought too much rather than too little! You're going to need thinners as well; don't bother with the 'standard thinners' paint shops sell; ask for 'top-gloss' thinners, it costs a little more but is worth it (just ask to guy in the paint shop). It comes in 5 litre cans, I would buy two - you wont use it all for spraying but it's handy to have.
OK, so you're ready to paint. First you need to mix the paint. Blow off the dust from the lids of the paint and thinners first, and then mix 50% thinners 50% paint and stir very well. Often people filter the paint into the spray gun, and it's worth doing this. The paint shop will sell you some special filters for this. Now, you need to set your gun up. Follow the manufacturers instructions for this as it varies from gunto gun, but you basically want a nice wide spray pattern, with not too much paint coming out.
The good thing about a car like the Citroen DS is that you can remove all of the panels and lie them out flat to paint them. This helps to stop runs and makes it easier to build up a thick coating of paint. I'm painting each panel individually on this car, it's much easier this way if you don't have much space (or time). So, lie your panel flat and begin painting. I always paint the edges first, and anywhere where paint is likely to build up. If you don't do this, you're more likely to get runs, and more likely to get a thin coat on the edges. Paint the entire panel, in overlapping horizontal strokes. You're looking for a very thin coat on your first pass, you should still be able to clearly see the primer through it.
Now, wait a minute or so and repeat the process. On the DS, I've given each panel about 7-8 coats of paint. This gives a deep colour and importantly provides enough paint for cutting (more later).
OK, so you've applied 7 or 8 coats of paint and your panel is now the colour you want it. At this stage I'll often mix up some really thin paint, say 75% thinners to 25% paint and give the panel one final 'wet' coat. This helps the paint melt back and give a really flat surface. Now clean your gun and put the panel somewhere safe to dry. The paint should be touch dry in a few minutes, but I'd leave it at least an hour before touching it.
If you're painting a light colour, such as white or yellow, your panel should now be looking very smart. If you've done a darker colour, you may not have the finish you wanted. Either way, if you're painting at home you'll no doubt have encountered some problems with either bits in the paint, or runs. Don't panic! The next step will solve that for you.
When you look at a top-notch car, you'll see that the paint is perfectly mirror like and flat. If you look at a cheaper car (and I include cars such as new VW Golfs and Audis in this) you'll see on very close inspection that the paint has a slightly 'bubbly' surface. This is known as 'orange-peel' and is often difficult to avoid when spraying. The final wet-coat helps to avoid it, but you'll be very lucky to have escaped it completely. The secret to the perfect finish is colour/wet sanding.
Modern car manufacturers don't have time to wet sand every car they build, they rely on two-pack paint which gives a near-perfect finish out of the gun, but for a classic car, you have the time and you want to use it. The basic idea is that you sand the top layer of paint down which removes the orange peel, and then polish the undercoat up. This can take a lot of time, and I once watched someone spend 100 hours doing this on a Classic Ferrari! (No, I didn't watch all 100 hours...) Here's what to do:
- Take some 1200 grit wet and dry paper and wet it thoroughly. If you paint is basically good, rub a little soap into the paper as well to lessen the abrasive action.
- Making sure that you keep the panel wet at all times, begin sanding USING A BLOCK. You'll see that the paint starts to go matte, but you'll also see the imperfections disappearing. All you're looking to do is sand until the surface looks completely flat. You need to make sure that you don't get any debris trapped under the sandpaper which would leave scratches, so keep washing the paper out. I always have a hose when I'm colour sanding, that way you get a continuous stream of water with which to wash the panel down.
- If you go through the paint, you'll have to apply a few localised touch ups. This is no problem, I've done it myself and it will be invisible when the job is complete.
The Paint Has Been Flatted and Is Ready for Polishing
- Once the whole panel is done, it will look quite matte, with sanding marks on it. Now use some rough cutting compound such as Farecla G3 (available from the paint shop) on a wet sponge to cut the entire panel back.
- At this stage your panel will still look quite matte, but the sanding marks will have gone. Now take some very fine cutting compound, T-Cut is excellent for this, and polish the panel. You'll find this really hard work by hand, so a polishing mop on a power drill, or ideally a polisher, will help here. Be very careful with any power tool, you will burn through the paint quickly unless you keep the tool moving at all times. I'd recommend practicing this before doing it on the real panel.
- Your panel should now have a deep gloss to it. If not, repeat the t-cut stage until it does.
- Now you need to protect the paint, so apply a good few coats of hard wax such as Turtle Wax to it.
The Colour Sanded Panel
Some Final Words of Advice
Hopefully this shold have inspired you enough to try painting a car yourself. Excellent results are achievable at home - I do all of this on my driveway, it just takes time and patience. Some final words of advice:
- You're going to get overspray on anything nearby, so make sure you cover any cars, buildings, gardens etc before you start.
- Wear a mask! You'll poison yourself otherwise... (Seriously. Wear a proper mask).
- Wet the ground around the painting area, this helps to keep dust down and makes overspray easier to clean.
- Choose a still day. Wind will cause dry spray and drive you insane, trust me! Also, try to avoid very hot days or damp days. Both will ruin your finish.
- Make sure your neighbours don't mind you spraying outside - you will get clouds of solvent everywhere; if they're outside having a party they're not going to be impressed...
- Store your paint carefully. Cellulose is explosive, and thinners is highly flammable. Keep it in a locked cabinet.
- Always keep your gun scrupulously clean. After any spraying session, dismantle and clean it, then store it carefully. There's nothing more annoying than a gun which splutters paint everywhere because it's not clean.
- Don't panic! If things go wrong, flat the panel and correct it. The only major concern is silicon. If you get this, you'll have to flat down to the metal and start the affected area from scratch. Anything else can be easily sorted.