How to paint: part three
At last – we get to spray! But is it all worth it?
Finally, we get to paint! But there’s a reason professionals charge good money – it takes time to get good at it, it takes money and it takes patience. Is it worth it?
Finally, our hard work and perseverance of preparing the panels and parts for painting can pay off. Our final pieces are either in bare material or, if we know what they were painted in, rubbed down for a keyed surface. It’s now time to spray.
Why not aerosol paint?
Most of us have used aerosols to paint before. Providing they are of good quality and are prepared (warm enough and thoroughly mixed by shaking – THOROUGHLY shaken!), they should give a good coverage with a uniform finish. They mostly use cellulose paint, which has the benefit of not needing to be mixed with a hardener as it is air drying. But that does mean you have to put on thin coats so it dries or you’ll get runs. It is designed to give a decent finish without lacquer, but you’ll need a lacquer coating to protect from petrol. I have seen a two-pack spray can which mixes actuator with the paint, but never used one. Aerosols don’t, however, need cleaning afterwards – a major bonus!
Spray guns
Spray guns need a compressor fitted with a moisture trap. Most common guns now are gravity guns, where the paint is held in a container at the top. There are many different sorts and prices range from £15 to £1500 – and they look the same! I use a £25 Sealey 1.8mm (spray hole size) gravityfed gun for primer work and a secondhand DeVilbiss 1.3mm gravity gun, which cost around £100, for top coat and lacquer (or clearcoat as Americans call it – because it’s clear…).
The difference is amazing; the Sealey one blocked up because the coating was coming off the aluminium body and everything feels cheap. The old DeVilbiss, which has led a hard life as a professional gun, feels like new and is a pleasure to use.
Paint
There are a number of different types of paint. Most commercial bodyshops have to use water-based paint systems, but classic and bike painting can still use solventbased paint. Also called 2K, or two-pack (as
the paint is mixed with an activator and thinners) it is, for many, the best method for bikes due to a nice finish. It is hardy and will cover many different surfaces, like steel, aluminium and plastic.
The parts generally need three or four different coats – an initial layer that helps to key the surface, acting as a barrier and as a gripping surface, then a primer layer to fill in any minor imperfections and leave a smooth base for the colour layer, which may also have a lacquer on top to protect.
Etch primer (gives a key for paint to grip to).
Filler primer, or high-build (gives a thick layer to fill any minor imperfections).
Base coat (the colour – looks satin finish). Lacquer (or clearcoat – gives the shine and protection).
Find your local professional paint supplier and tell them what you’re doing. They should be a useful fount of knowledge for how much of what to order, what works best, and how to use it. But remember they are professional suppliers, not a DIY helpline.
Other equipment
You will need a host of other goodies.
First, somewhere to spray. This should be unaffected by wind or drafts, yet preferably ventilated. I use plastic sheeting around and above the area in the workshop, but must improve my ventilation if I’m to do any more than just small bike parts. I also sweep the floor an hour or so before, then wet it with a watering can to prevent dust or dirt hanging in the air.
Light is essential, which is why professional booths look like a tanning shop. Florescent strip lights are best for showing up problems or the finish, and you cannot have too many.
You need something for the parts to be held on, but that won’t mark them. Welding wire is handy for hanging parts, while I made a weird stand ‘thing’ out of old steel, as bike parts like mudguards, oil tanks and stays are tricky. The pressure the paint comes out at will move the parts if not secure.
Although 2K paint will work in a wide range of temperatures, I have a room heater for the air and a hot air gun to heat up the panels before and during painting.
You will also need masking tape, panel wipe and rag to remove any grease from your fingers, or anything that may cause the paint to react. You then need paint measuring glasses which help with getting the right mix, stirring sticks, 2K thinners and some paint sieves to prevent any lumps going into the gun.
You’ll also need a good breathing respirator mask, as two-pack paint contains cyanides, while a plastic overall will help prevent fluff getting in your paint. Get some goggles, and plastic gloves are good, but they will disintegrate in thinners when cleaning the gun.
Cleaning up afterwards
After mixing the paint, pouring it in the gun and spraying the part, you need to clean the gun. The quicker you do it, the easier it is. You can buy gun cleaner, but it’s just recycled thinners – it’s as cheap to use cheap thinners – though be sparing.
Strip them all down in a baking tray and use pipe cleaners, bottle brushes, rag and thinners to give everything a good clean. Filler primer is the worst and takes the most time. Use an air gun to blow through all the jets, then leave it all to soak.
What do you do with all the thinners?
This is a tricky one, as thinners is a nasty chap. You will need to check with your council, who will treat it as hazardous waste, so you will end up paying to dispose of it. Please do though, as it kills most things it touches and going down a drain is irresponsible. I keep it for cleaning as it is superb for unpainted parts like carbs, calipers and oily parts, especially with a toothbrush.
Mixing your paint
The different paints need different mixing. Etch primer doesn’t have to be a thick layer; it just acts as a key to hold the paint to the panel. I mostly use an aerosol for this, as most bike parts are small. It saves time and thinners cleaning the gun.
Then its filler primer, or high-build, as some call it. As you’re putting more material on than etch, it’s best done with a spray gun. High-build is mixed with activator to make it go off; you can also thin it with thinners to give a different finish – I tend to thin by 15% in winter and 10% in warmer weather.
Use the plastic measuring glasses to get the ratios right – the primer I use is 4:1, but others may differ. Then stir and stir. And stir again – many issues with painting is poorly-mixed paint.
Once dry, you may find you want to rub down a bit of grit, or an area that is slightly ‘orange-peel’, so use a 800-1000 grit wet and dry most carefully. It is so easy to rub
through the primer to the metal, especially on a crease, or the edge of a mudguard, where you’d have to do it all again.
This is a classic example of why it takes time to learn how to spray. Re-wipe the panel once you’re happy in preparation for the top coat – primer is porous, so don’t leave it too long before applying the base coat.
Finally it’s time for the colour, but no need to rush it. Basecoat is thinner than high-build primer, hence use a finer jet – 1.3mm in my case. Basecoat is easier to apply than colour from an aerosol, is mixed 1:1 with 2K thinners, and is delightful to use. Once thoroughly mixed, use a paint sieve to pour the paint through into the gun. Pop a dusting coat on first, to help it stick on. Then apply a coat and let it rest for 10-15 minutes. Let each layer rest a few minutes before applying another. If you see any dirt or runs, let it dry fully – around an hour at least – then rub down gently as before and reapply the basecoat. Try not to touch the finished basecoat once you’re happy. It should look disappointingly flat or have a satin finish. It is also porous, so lacquer needs to go on within a reasonable timeframe. The 2K lacquer I use is 2:1 lacquer to hardener, then 10% thinners. Pop a light coat on first, waiting a few mins until it has started to go off; then your layers can be thicker.
While lacquer can be rubbed down, the better the finish from the gun, the better the panel will look.
Technique
Using a spray gun takes time to master. And so often we only spray when something needs painting – we don’t practice enough. There are a few ways of tuning the gun, so take a piece of card to practice on. The top dial adjusts the amount of paint coming out when the trigger is fully squeezed – the triggers are variable, which really help. The lower dial is the fan – how wide or narrow the spread of paint is. It’s not a circle, but more of a line of paint. This helps prevent overspray and on bike parts can be narrower – but then you may wish to turn down the amount of paint coming out. The main jet has two side jets; if they are horizontal, the spray pattern will be vertical, and vice versa. The last control on most guns is at the bottom, which adjusts how much air is coming through. The more air, the more paint is needed, but the easier it is to put too much on and get runs.
But don’t be afraid! The dials will quickly find their happy place and stay there. Only if you change paint will you need to adjust. Quite simply, the more you practice, the better it gets. But the more it costs…
A spray gun isn’t light, made worse by the fact that an airline is attached and you mustn’t touch any of the panels you’re
spraying! Like our example mudguard, try to practice how your hand will move around to cover the whole panel, while keeping the same distance away. Also plan where you will paint and in what order – I sprayed the inside of the mudguard first, then the edges, then finally the outside, each time I did a layer.
Look at the panel as you’re painting by getting the light in the right place. That way, you can see the finish more easily. As you apply the paint, it settles. Straight from the gun it may look a little like orange peel, but give it a few seconds and it will settle to a smoother finish. If you’ve applied too much paint, you may see it slump and slowly run. Only time and practice will teach you this.
If you see, quite quickly, that the base coat is reacting, there are two possibilities. One is that something below has reacted – grease or something on the primer, or even something seeping through the primer from below. The other possibility I’ve seen is too much paint applied too quickly. If you feel you have done this, try using a heat gun after each layer – it may help evaporate the thinners more quickly. Either way, it all has to be rubbed back to primer and started again.
Is it worth it?
I love painting panels. The satisfaction is immense, and it’s another job I don’t need others to rely on. But we have the space, we have cars, bikes, tractors and other things that can be painted, and I have learned over the years from people who really know how to prepare and paint beautifully. But is it worth it?
I’d have to say no. The financial outlay for painting a bike is hundreds of pounds. You need space, and you need to practice. And practice. And practice... which costs time and money.
But all is not lost! All that preparation will not go to waste – it will save money when you go to a bodyshop. And the fact you know what is involved means you understand why you are charged what you are. You’re paying for time, patience and years of learning.
I feel bad coming to this conclusion and if a few of you can get together, then that may be a better idea. But if you get a chance to do some spraying, give it a go. The feeling when you get it right is worth it.
One last note: this is how I do it. Any professionals out there, please share your knowledge with us. The idea of this feature is to show how possible it is to paint your own panels, but also to highlight the issues. Any advice gratefully received!