Difference between revisions of "Spray Painting"
Revision as of 18:29, 7 February 2005
Hey mate, first in reply to Benneth, no, the thinners is for mixing with the flat black and undercoat, NOT for removing the paint. Ok any Auto One, Autobarn, Super Cheap etc type outlet should sell paint, thinners and undercoat as well as the Automotive Paint outlets. You should need approximately 4 litres of Acrylic Primer undercoat, 4 litres of Flat Black, and a 20litre drum of thinners, you won’t need all the thinners for the paint but you will use it for cleaning the gun after use etc. You will probably use around 10 rolls of 1/2inch masking tape to back tape and tape everything up. Grab a few Paper masks to stop you inhaling the dust from the acrylic paint, the ones with two yellow rubber bands on, not those useless ones with a single thin strand of elastic. It may pay to grab a litre tin of wax and grease remover so you can wipe it over with a clean cloth and wipe off with a dry clean cloth to remove any traces of wax, grease from finger prints, hand prints etc, you would be surprised how well a hand print will show up in the finished paint if someone especially has been eating chicken before helping you rub down. Normal rule of thumb is to mix 1/3rd paint then 2/3rd's thinners to get a mix that doesn’t spray on to dry nor too thin and runny, don’t fill the pot all the way to the top otherwise when you tilt the gun the paint will dribble out and onto your paintwork. If you stick with Acrylic paints any mistakes are very easily rubbed out with water and the use of a small rubbing block. Super Cheap sell good 1/2 Sheet Sanding blocks, they’re normally a reddish orange in colour with metal clips on each end and take half a sheet of paper, these help a lot to get the panel sanded flat, remember to use the flat part, never use edges or corners of the block to sand with unless you want ripples and stripes through out the finished paint job. You will need to first rub your car down with 800 wet & dry paper using a hose lightly running water over the all the paint work and whatever else you wish to paint as you are sanding, water prolongs the life of the paper as well as helps to stop it from clogging. When all your paint is a satin finish, that is you have sanded the shine from it, you will then need to wipe down and dry your car off then start back taping your car. Time and patience is needed for a decent finish here. Firstly using the masking tape (white paper tape) back tape carefully along the insides of your doors and rubbers etc so the paint wont spray into your cars interior, same along the inside edges of your front guards, boot etc, you only want the paint on the outside of your car ok, so carefully apply the tape so paint will not get onto or through any of the door gaps or on the window rubbers, chrome strips, glass etc. You can use newspapers to back tape, run a piece of tape half along the paper so there’s half showing, then apply the taped piece of paper you have around the insides of your door frames, centre pillars, inside the bonnet and boot then do the same and tape over all your windows by taping firstly around the edges then filling in with layers of newspaper. Tape up door handles, locks etc if you haven’t removed them or leave them if you have sanded them back so they are the same colour. Then when you have mixed your undercoat and thinners (1/3rd undercoat + 2/3rds thinners) stir with a steel ruler or similar to make sure its mixed well, place the top of the gun on the pot, screw the air pressure up to around 60psi depending on your compressor (ideally at least a 10CFM up) or how long your air hose is so when you pull the trigger you have a nice even fan spray of about 15cm's wide. You can test the spraying technique on an old wall or board etc, what you want to do is hold the gun approximately 30cm's away from the panel and to pull the trigger before hitting the panel and letting go once you have passed over the panel. So say for instance, you are spraying the drivers front door, pull the trigger on the front guard and gently sweep to your left over the door onto the front of the back door then stop, then pulling the trigger pass to the right over the front of the back door back over the front door back onto the back of the front guard, stop then pull the trigger over the back of the front guard then to your left over the front door back onto the front of the back door. Repeat this process over and over each time making sure you are overlapping the last spray by half so effectively you are double coating the panel with each pass.
top of 1st spray.______________________________________.top of 1st spray top of 2nd spray.______________________________________.top of 2nd spray bottom of 1st spray.___________________________________.bottom of 1st spray bottom of 2nd spray.___________________________________.bottom of 2nd spray
When the car is completely covered in undercoat and has dried off, spray a light even coat of the flat black over it all as a guide coat, and do not get carried away because the aim here is too sand off only the black off WITHOUT rubbing through to the original paint. Guide coating is an effective way of rubbing back the paint again using water and again using the ½ sheet sanding block, sanding in nice smooth arm length gentle strokes, criss-crossing ‘X’ style so you are not sanding back and forth sanding grooves into the undercoat, you will see how effectively the trace coat comes off, no need to go any further. Then, when it has had the trace coat sanded off, pull all the old tape off, wipe down with wax & grease remover, dry off then repeat the back taping and taping paper over everything again. Fun hey? This is why painters and panel beaters earn their money, on it goes off it comes, on it goes off it comes, again then again then again lol Then once it has all been taped up ready for the flat black, wiped over with wax and grease remover, clean rag for on, clean dry soft rag for wiping off, no nylons, t-shirt material is good (without the transfers) wipe it over with a dry tack rag to remove dust and lint etc (available from most paint places) Then mix up the Flat black acrylic paint into the paint pot, 1/3rd black, 2/3rd’s thinners, stir, lock the gun down then get into it. First I like to go around all the parts where the paint will be light during spraying and coat these parts first, like under the sill panels, front stone tray, rear beaver panel, under the guards etc. Everywhere you think you will forget to get down and spray during the process. When getting into painting I prefer to start at the top of the roof starting in the middle on one side and working my way back to the gutters spraying from front to back overlapping each coat as I go, this I was taught pushes the dry dust from the paint down instead of up finishing up with a rock hard dry cement like finish/ stripe in the centre of the roof. Then once the roof/ rear pillars has been painted, repeat the process and coat the roof again then when finished work your way to the bonnet and again work your way from the middle to the top of the guard , then do the other side, then the boot lid the same way. During this you will need to refill the paint pot often, its always good later into the paint work to have a buddy watching to tell you where you left off when you ran out of paint. I normally spray over each panel over lapping once, then repeat this again, this effectively lays 3 or 4 coats of paint on in each pass of each panel. By the time I am finished I will have done this a total of three times and if done correctly those three times will equate to six or 8 coats of paint, the reason I go around once, then again a second time, then a third is it gives the paint time to flash off so when I come around to that panel again it is dry enough yet still wet enough to take another coating and let the layers blend and bond together. You will work out that spraying over a panel too fast will result in a dry finish, but spraying over too slow will result in a too wet finish resulting in runs, the secret is too work fast enough yet slow enough to lay down nice wet even coats that will flow and blend into each other. Once the roof, bonnet and boot has been covered I then start at say the left front guard, then work my way to the left front door, left rear door, left rear quarter panel, rear beaver panel, right rear quarter, right rear door, right front door, right front guard then finally to the front stone tray. Then I go back to the roof for pass #2, repeat the process until I get around to the front stone tray again, then go for pass #3. By this stage your arms feel like you have gone a hundred rounds of arm wrestle with the Terminator and your legs feel like jelly lol Then it’s a matter of clean out the gun, wipe the pot out, pack everything away, crack a cold one then flake out on the front verandah for a while lol (If you are a Queenslander lol) Then the next day its up early, carefully remove all the tape and paper, refit whatever you took off to do the painting then roll her out into the light of day! Once you have come this far, this is when flat black becomes fun, you get the bug and next thing you will be taping up and spraying scallops on one week, then next week rubbing that back then experimenting with flames etc Flat black is like a blackboard, only your imagination can stop you and if you are adventurous enough you can have a different paint job every month lol Obviously as you will realise there is a lot more to this and this would have to be the condensed version, but spraying is fun, spraying acrylic can be very forgiving as unlike enamel if you stuff up it’s a matter of rub back and recoat, you wont need to sand the whole car down, acrylic is not as deadly as two pack paints, but always wear a mask, preferable one with a filter if you are going to do this often, but mate its your car, have some good clean fun, this is how I started out and partly taught myself a trade before someone was willing to take me on so it does have its benefits too. If I missed anything (Dayamn!! lol) ask away and I will hopefully now have a shorter answer for you lol