Introduction
I looked around and there seems to be no thread about how to spray paint here, so i thought 'why not make one?'
I work for a certain Italian supercar company that uses a little horse as a logo, i don't paint cars everyday anymore but during my apprenticeship (2 years ago) i had to study paint, bodywork and painting technique.
I'll also talk about different types of paint and the advantages and disadvantages of each.
Types of Paint, Their Advantages and Disadvantages
Paint comes in many types, the most common are Lead based, Polymer based, Water based, Gelcoat and Powdercoating.
Lead based paints are old fashion which takes many hours in a oven to cure. Due to the fact that they take so long to cure, they also do not require a clearcoat to give a glossy surface (you can if you really want colour depth). If you have studied chemistry then you will understand why.
Lead based paint were used on cars in the old days, but as monocouqe cars became more popular lead based paints were not used. Why? because lead based paints are very hard and can crack when the monocouqe shell flexes during high speed corners, or when the bodywork gets hot and expands.
Lead based paints are also very toxic, so a mask with charcoal filters is highly reccomended when using lead based paints.
The most common type of polymer based paint is Acrylic paint, acrylic paint is also quite hard, therefore it will not scratch as easily as water based paints, but will crack if flexed too much. Commonly used in model making it is easy to use and not toxic. However, i still reccomend you use a mask.
Due to the way the polymers arrange themselves it is also quite easy to get a glossy surface without clearcoat, again if you really want colour depth then you will need clearcoat.
The largest portion of water based paints is auto paint (paint you use on cars). Water based paints are flexible so they won't crack as easily, but is also very soft and will get scratched just by rubbing it with a cotton cloth.
Water based paints can give a semi glossy surface if delivery in a large amount but teardrops (paint sliding off the surface) will start to become a problem. The solution? Use just enough paint to cover the surface then add clearcoat.
I don't have much experience with gelcoat or powder coat so i will not comment on them just yet. Maybe in a latter update.
Painting a Computer Case
There are different ways to paint different things, first i will do a step by step guide on how to paint computer cases (since most people here are more luckly to paint a computer case than a car). If i get loads or requests on how to paint other things for example then i will add them latter.
Step 1: You will need your case obviously! Most cases are powder coated so this is a very good base to start with. So get some 800 grit wet and dry, a sanding block and start sanding any surface ripples. When using wet and dry always use plenty of water, not only will this stop dust from flying it will allow you to see the surface you're working on. If you find there is alot of resistance between the sand paper and the surface you're working on than you can add some washing liquid to the water you're using.
Note: When using 800 grit do not sand through the powder coat! If you do happen to do so after you have painted the case there will be a imprint of where you have sanded through the powdercoat. To save it you either have to sand back all the powder coat until you are left with the primer or back to bare metal. You really don't want to do either then your only option is to use putty. *Guide on how to use putty is at the very end*
Then spray a very thin layer of paint on top (choose a colour that has high contrast again the colour of your putty) and start sanding with some 1200 grit wet and dry. While sanding you will notice any high spots as those places will loss the paint you just applied faster than the low spots. Repeat process until you think you have a perfectly flat surface.
Step 2: If you sanded all the way back to bare metal then you're going to have to use acid etch primer so your lovely paint job does not flake off in the future. Always use gloves, goggles and a mask when dealing with acid etch primer unless you really want your lovely paint job to continue from your case on to your limbs, it contants sulphuric acid which eats into the metal to give a really good bond.
If you didn't sand back to bare metal or have already added acid etch primer, then you will need to add high build primer. This serves the purpose of filling in some surface defects, aswell as giving the paint a good surface to grip onto.
Spray just enough to cover the entire surface then let it dry for it's reccomended drying time.
If you do see any ripples/surface defects/teardrops or in general just want to go that extra step, sand it with 1200 grit wet and dry. Then 2000 grit to smooth out the scratches you added with the 1200 grit. Remember, any defect you leave here will show through at the very end, so make sure it's perfect.
Step 3: Now onto masking. Mask all places you do not want covered in paint. Use masking tape developed for painting they are flexible, will not leave a sticky residue when pulled off, and has a very low stickyness so it won't pull off existing paint if you're going for a fancy paint scheme.
If you can't find them or think their too expensive then there is an alternative, take ordinary masking tape and drag the sticky side over your t-shirt. This will lower the stickiness of the tape, and is very ghetto if you're into that sort of thing.
Step 4: Now you get to do some spray painting! For computer cases i reccomend using acrylic paint and not a water based paint (like auto paint). The reason for this is that acrylic paint is more resistant to scratching aswell as being cheaper than water based paint in most cases. The final outcome between the two is going to be the same.
If you're spraying with a spray can then make sure you give the can a good shake before you use it.
Find a clean spot away from any flames when you start spraying.
When spraying with either a airgun or a spray can always start spraying off the surface of the item then bring it over the top of the the place you want to paint, then stop the spray when the paint is not spray on the item. Then continue the in the same way until the whole surface has enough paint just to cover the surface, and let it dry for atleast the reccomended drying time more if possible.
You may add multiple coats of the same colour if you want, but there is no real gain in doing so.
Step 5: Inspect the surface under a good spot light (or a torch) to look for defects (dust spots, orange peel, or ripples where you didn't give the surface enough paint). If you don't see any and think it is perfect then you can proceed to using rubbing compound. *Guide on how to use rubbing compound is at the end*
If you have defects then you will need to get out some 2000 grit wet and dry again and start sanding. Sand the problem areas until the defects are gone, take care in not sanding through the paint, if you do then it's putty time again then applying more paint.
Step 6: Now that the surface is perfect you can add clearcoat. Clearcoats come is two main types, fast curing and slow curing.
Fast curing types are designed for DIYer, the surface is softer which means it will be sratched more easily, aswell as being not as reflective.
Slow curing type is designed for professional use, it alot harder and alot harder to work with aswell as taking several hours in a oven just to dry (not cure). However, it's alot more rewarding if done properly.
Applying clearcoat is done in the same way as applying the coat of colour, start spraying off the item and stop spraying off the item.
Spraying multiple coats of clearcoat will increase the effect of colour depth, but if you have dust spots or any imperfections then you will need to sand with 2000 grit wet and dry then use rubbing compound. You may also notice some defects in the coat of colour now, which you did not see before this is due to the clearcoat acting like a magnifying glass and making any imperfection very obvious, the only solution is to sand the whole thing back to the coat of colour. So make sure you get the surface perfect before you do clearcoat or you will have to start over again.
Now that you have finished takes loads of photos to impress your friends!!
**Extra Guides**
How To Use Putty
There are again quite a few types of putty, i love to use epoxy putty, they won't pop out like some other types of putty would when flexed too much, but they do come at a price.
The key to using putty is to get a flat surface and getting the mixture correct. There are loads of different types of putty knives to choose from, any type would do. Of course choose a size that is bigger than the area you are doing, you will find it very hard to apply putty on an area the size of your palm with a putty knife the size of your thumb.
However, if you want to cover mistakes like sanding through the paint then you will need a putty knife that is hard and not flexable, just to get a very small amount of putty inside the indent.
After the putty has dried, spray a very thin layer of paint on top (choose a colour that has high contrast again the colour of your putty) and start sanding with some 1200 grit wet and dry. While sanding you will notice any high spots as those places will loss the paint you just applied faster than the low spots. Repeat process until you think you have a perfectly flat surface.
Rubbing Compounds
I normally don't like using rubbing compounds due to it causing loads of micro-scratching, but sometimes you're left with no choice only use rubbing compounds with a high speed polishers and then a orbital polisher. Applying by hand will leave localized scratches which looks like there's a dull patch.
I'm also not goin to reccomend nor not reccomend any brand of rubbing compound or it would most likely end up into a argument.
High Speed Polishers
High speed polishers are basically, angle grinders with large foam pads or lambs wool. The main use of a high speed polisher is to remove material.
The old fashioned way is to squeeze an amount of rubbing compound onto the surface you're working on and then use the high speed polisher with a lambs wool attachment to work the compound. This is the INCORRECT way to do it, new compounds have been developed and new foam pads are appearing monthly. They just get better and better.
The modern way of using a high speed polisher is to contact a company called System One, and ask for a set of their compound and foam pads. Their compound is one of the new types of compounds that does not carry abrasives. My guess is that their foam pad does the cutting, and the compound acts as a lubricant as well as filling in the micro-scratches left by the high speed polisher.
If you're looking for a good brand polisher, Makita has some of the best around.
How do you use a High Speed Polisher correctly?
1: Pour a amount of compound on to your surface. The amount will depend on the surface area, temperature, humidity, as well as how porous the surface you're working on. The judgment will depend on you're experience. Normally between a radius of 1-2cm.
2: Turn the high speed polisher's speed to 1 (lowest) and place it flat on the compound as close to the center as possible without letting the compound get into the hole at the center of the pad.
3: Slowly, pulse your finger on the on\off switch, to gradually bring the speed of the polisher up (this will prevent compound splashing all over the place, hard at first but practice will make perfect), once at full speed dial the speed up to around 2 or 3 on the makitas. At first you will find it very hard to control the high speed polisher, as it will move around on it's own, as well as being heavy in the first place.
4: Separate the area you want to work into areas, and target each areas one at a time. Never place the high polishers on the same spot for more than a couple seconds, this will burn the paint.
Areas with a lot of micro-scratching or orange peel use a bit more force. Stop when compound dries up or dust starts to appear, then reapply compound and continue.
Tips
Use the center of the pad, never use the tip! Using the tip will make the machine jump and move around a lot more. Obviously if the machine jumps then the surface won't be perfect.
Orbital Polishers
Under Contruction
