Greetings from the UK!
I'm an utter noob here, however I work with commercial spray paints on a daily basis respraying everything from plastic to metal and laminate surfaces. I know a lot of the basics have undoubtedly been covered here but I'd just like to reitterate several fundamentals when it comes to respraying, rules that essentially I swear by and that I think will come in handy for anyone looking to do a custom spray job on their keyboard, or anything else for that matter.
1) Preparation
I know this is the really boring part and whenever we begin a project everyone has that urge to just grab the paint and get busy, but I cannot emphasise enough the necessity of putting time and effort into preparing your surface. Ideally all surfaces that you wish to paint should be sanded to a fine degree and thoroughly cleaned and brushed down so as to be clear of all grime, dust and detritus, paying particular attention to burs and moulding marks on corners and edges. Previous posts in this thread seem to have it spot on in terms of what type of sand/glass paper to use, however a quick and easy alternative to sanding can be fine sand-blasting should you happen to know of anyone with the appropriate facilities.
2) Location
The location in which you choose to conduct your re-spray job is very important. You should have available to you at least one flat surface and one wall against which to rest your keyboard case. This should preferably be either indoors or in another form of 'still air' environment (i.e. garden shed, greenhouse or garage). Additionally, if this is not a designated painting area and getting paint everywhere is a problem you might want to consider covering these surfaces with well taped-down material such as newspaper or ideally cardboard or plastic. Always cover a greater surface than you think you need to because spray paint does have a tendency to travel and the last thing you'll want is to end up doing is repainting the entire garden shed fluorescent green because Mum, Dad or Auntie Doreen did not appreciate the creative finesse of your accidental overspray. Again, having masked the area ensure that any dust, dirt or debris is removed from the surrounding environment in which the painting will be taking place.
3) Climate and Temperature
Of key importance to any spray painting project is the climate and ambient temperature of where you choose to paint as paint particulates react to whatever atmospheric conditions they encounter upon leaving any form of compressed spraying device. Consequently if you spray in wet or cold conditions spray paint, like any liquid medium, is prone to condense 'mid-air' and will therefore leave your incredibly well prepared and buffed down surfaces with a very obvious bobbly, dimpled or stippled effect. Therefore ideal temperature conditions should be between 17 and 25 degrees centigrade (sorry for those not in the UK I'm not sure what the Fahrenheit equivalent is). And once again I cannot emphasise enough the importance of spray painting in a still air environment. Personally I am fortunate enough to have access to a proper spray painting booth with an extractor fan so if you, or anyone you know, has access to similar facilities I'd highly advise making use of them if you can. Obviously though the vast majority of us will not have such facilities in which case finding an appropriate location where you can avoid drafts and sudden gusts of wind is vital - certainly try to avoid areas in hot direct sunlight, under trees or anywhere your pets might have easy access to because picking out bits of leaves, dead bugs or pet hairs (or anyones hair for that matter) from a half completed paint job is a chore best avoided.
4) Ventilation
When inhaled commercial spray paints are damaging to your health so before doing anything ensure you have an appropriate mask to prevent you inhaling fumes and particulates. Your cheap DIY dust mask will normally do for the odd small job here and there however if you plan to use spray paints on a large project or on a regular basis the I would highly advise investing in a decent particulate mask with replaceable charcoal filters. Additionally, while as I mentioned,you should ideally be spraying in a 'still air' environment it should nevertheless be a place with adequate ventilation to allow fumes to escape.
5) Paint Prep
While all off-the-shelf spray paints come ready mixed they often spend a significant part of their lives either sat in boxes or on the shelves of your local paint/DIY store. As a result this can cause any paint (even polymers and enamels) to congeal and separate, the heavier particulates sinking to the bottom of the can and the lighter at the top. This process can also be exacerbated by their being stored at varying degrees of temperature. Therefore before using any type of spray paint it is firstly very important to ensure that the can is at room temperature and, secondly, to spend at least 5 to 10 minutes agitating the can so that the metal ball inside does it's job of returning the paint to an even consistency. Ideally you should shake the can vigorously for the fore mentioned time or at least until your arm starts to actually ache (or you get what we call 'wankers cramp' here in England) before swapping to your other arm for an equivalent amount of time.
6) Setting Up
So once you've ticked the boxes in terms of location and paint prep you'll want to set up your case ready for spraying. As mentioned earlier in this thread it is important that you do not spray your case while it is lying down horizontally. Ideally, your spray paint can should always be held at right angles - a vertical 90 degrees to the surface you wish to cover. It may sound obvious but doing this will ensure that the paint is always delivered from the bottom of the can and therefore your paint feed will not be interrupted, sputter or spit as a result of the air inside the can entering the paint feed. To work against this take your case and lean it against your wall vertically ideally with it base (the shorter edge) on something other than the floor. I normally rest whatever I'm painting on a wire basket or plastic bottle crate which are both useful as the ridges prevent leaning objects slipping mid-spray while also allowing any overspray to pass right through and not pool at the base of the surface I am spraying. Not doing this and simply placing your keyboard cover on the floor, or in fact any smooth flat surface, will inevitably lead to overspray bouncing back up onto your cover from that same surface and thereby create an uneven delivery while also inconveniently adhering whatever dust and dirt has remained on the floor/surface to your lovely paint job.
7) Technique
Once again to reiterate a point previously made in this thread the key to a consistent spray job is to build up layers slowly... ever so slowly... in a series of very light layers. I cannot emphasise this enough!!!! Your first coat, regardless of colour, should hardly be noticeable and should, at most, only show up as a very light 'misting' upon your well-prepped surface. If you are worried that you will run out of paint then please please please just let let the paint run out as opposed to trying to cover it all in one go. After all you can always buy another can of paint tomorrow if needs be and it's far better to take your time and do a job properly than expend extra time, effort and money because you rushed to get everything covered in one go only to create a horrible gloopy mess. Also be aware that as the paint runs out in your can the more likelihood there is that air will enter the feed. Therefore it is often wise to try and not use every last drop of paint in your can should it start spitting and spotting on your otherwise perfect paint job.
When starting to spray you should have your spray paint can at least a foot away from your cases surface (ideally slightly further for your first few layers). You should begin at least half a foot from the outside edge of your cover and move across it horizontally - left to right or right to left dependent on what feels best - only releasing your finger from the nozzle once you are at least half a foot past the opposing edge. While this might seem wasteful in terms of overspray it is nonetheless very necessary in that it will ensure your paint will hit your surface when it is at its optimum flow, and also reduces the chances of any unsightly drops or spatters hitting your surface due to temporarily congealed paint in the spray nozzle. It is very important that you maintain an equal distance across the spray plane as you make this action. Naturally your arm will want to make an arcing movement that will bring the can closer to the surface of your cover as you move your arm across your body. Being aware of this and resisting this natural inclination is very important otherwise more paint will condense in the middle areas of the case than at the edges.
Have Patience
When undertaking any spray painting job it is vitally important that you have patience and take your time, especially when it comes to building up layers to get a smooth surface. I personally have never seen a decent spray job that did not involve more than 4-5 layers (excluding undercoats) therefore having the patience to apply thin layers with sufficient 30 - 60 minute drying times (temperature depending) in between should be a pre requisite for anyone looking to do a decent job. There are several important things to remember here:
- don't attempt to rotate or turn your case until it is totally touch dry.
- instead of changing your angle to spray difficult edges and corners wait for your case to dry then rotate your case so that you cover these areas as part of your regular spraying action.
- don't try to patch over any areas you may have missed in between layers, just remember to cover these areas with your next layer.
- while the paint may be touch dry in a relatively short time it will not be fully dry for over 24 hours, often longer!
9) Drying and Finishing
Before attempting to do anything with your finished case it will need to dry for at least 24 hours. Once it has you may still find misting, stippling or fuziness across your cases surface. Should this occur simply take a clean kitchen cloth or sponge, dampen it slightly with water and give your case a very light wiping down and that should help smooth away some of the more pronounced differences in texture. If you are especially fussy your local auto parts dealer should sell special finishing cloths that auto spray repair experts use to remove these 'bobbles', however I'd advise against using these if your case is anything other than metal as some of them contain a chemical residue that may react with plastics. Another way to combat this problem is use a clear polymer lacquer to smooth away these differences, an added benefit is that this will also make your paint job a lot more hard-wearing. To apply a clear lacquer these simply follow the same procedure as you did with the painting, though this time be even more aware of giving your layers sufficient drying time as the last thing you want to do is ruin your perfectly finished case with a nice big finger print or congealed drip.
Hope this has been of some help and apologies for any typos it's been a long day, good luck.
