It is currently Fri Feb 22, 2019 4:36 am

All times are UTC + 10 hours

Forum locked This topic is locked, you cannot edit posts or make further replies.  [ 1 post ] 
Author Message
PostPosted: Mon Jun 14, 2010 2:09 pm 
ausmini admin
ausmini admin
User avatar

Joined: Sun Sep 23, 2007 6:12 pm
Posts: 245
Location: Under the bonnet
Thanks to Phat Kat for the effort of putting the How-To together.
Don't get me wrong however..God doesn't paint, he just creates a new car when he wants one with a freakin big lightening bolt.
Oh and while I'm on it..the evangelists are correct, I do create the crude oil..its limitless. So feel free to invest in a large petrol guzzling Viper or whatever tickles your fancy.

Alright, I'll just take this skirt off and get on with it.

This version (as the thread title suggests) is just a draft, so in the final copy will include the suggestions made by others in the thread and some photos.... and it I can work out how, some links to youtube with videos on it.

This how too is for a bare metal respray (the final will include metallics and repairs).

Oh yeah, and just for cush, I will eavn tri to ficks some of the spelling mistax Smile



tools & Materials

• Sand paper (carbide paper), in 240, 400, 600, 800, 1200, 1500 and 2000 (1500 and 2000 are optional)
• A rubber sanding block, and a soft block. For the soft block, I just use a 6"X 4" rectangle that I cut out of a thong (that’s as in foot ware thong, not a G string, this is Australia mate)
• Soft grade of scotch brite (maroon in the 3M range is quite good)
• 4lts of prepsol (also called grease and wax remover) you may have some left over but don't worry it goes great with orange juice.
• 4lts of Multi Purpose thinners (this is for mixing etch primer and cleaning.)
• 20lts of Acrylic Thinners. This only for Acrylic Paint, you can use it for cleaning but its not nearly as effective. You will need 20lts; you may have as much as 5lts left over but 20lts is cheaper than 3X5lts. It is maybe 10% more expensive than Multi Purpose but it is more refined than Multi. You will not get a pro quality job using Multi for mixing paint.
• 2lts of 1k etch primer (that’s 1 part or acrylic, "k" is the first letter of the German word for component, 1k one part 2k two part or 2 Pak).
• 4lts of primer surfacer
• 1lt of black paint or GMH Black if you like, this is for guide coat so it won't be staying on the car, it gets sanded off. GMH Black is a cheaper than full quality black paint. Another name for GMH black is body black. Its poor quality paint so only use it for guide coating
• A tack rag (you can get these at paint shops for about $2.50)
• 4lts of colour
• 1-4lts of retarder thinners (this is a slow drying thinners ideal for final coats of paint. If it is humid buy 4lts as you can replace 20% of your normal thinners in the paint mix with this and it will cure humidity defects)
• 4lts of clear (if a metallic is to be used otherwise just one liter)
• An air compressor at least 10 CFM, 16 CFM or more is ideal but 10 will get you by.
• Spray gun. For Acrylic people will tell you that you need a 1.8-2.00mm tip, but any size will do provided the Air/Material is adjusted correctly. As far as Suction feed guns V's Gravity feed guns go, originally gravity fed guns were the only HVLP (high volume low pressure) guns. Which meant that when you spray more of it goes on your job and less bounces off and goes into the air. It has been said that you save 30+% paint using a HVLP gun. Now days you can get both Gravity and Suction feed guns in HVLP. You can pick them by the number of holes in the nozel. A conventional gun will have 4-6 holes for the fan and one for the fluid, and a HVLP will have 8+ holes
• Cutting compound.
• Wax (make sure that it does not contain silicone. Silicone does give an unbelievable shine but it will cook your paint if it is in direct sunlight for extended periods or even short periods over a long time. It also makes it very, very difficult to touch up or repair paint work, you need to remove all paint on panel before repainting)
• A LOT of clean rags. You will go through these.

Lets get started!!!

We are going to assume that by this stage that all panel work is done. Any problems with bodywork must be rejected and sent back to the panel shop (so to speak). First I will cover solid colours. DO NOT SKIP A SINGLE STEP, IF YOU DON'T READ THE WHOLE THING, YOU MAY STUFF UP. IT WILL TAKE YOU 10 MINUTES TO READ THIS OR 20+ HOURS TO REPAINT YOUR CAR PLUS THE COST OF MORE MATERIALS.

1. Sand entire car with 240 grit, use the hard block on flat panels and the soft on ones with shape. Assuming that there is no paint on the car, sand dry, avoid getting water on bare metal for obvious reasons. If there is paint, sand wet. You will hear that most paint shops at the moment prefer dry sanding. This is because they can save time not having to wipe slop and water off the car and they wait for it to dry. But the only reason they are able to do it dry is because they are doing it with special dust extraction. With out it, the paper clogs and scathes the surface. The other way they do it dry is using Fre Cut paper. Proper Fre Cut is made by 3M, if you can't get 3M Fre Cut, don't bother. It does cost more than Carbide paper as well. For any of those hard to get places, where it is hard to sand, use the scotch brite. Inside the gutters use the scotch brite wheel, it's much quicker and easier.

2. Mix up your etch primer. Etch primer must be used on bare metal as normal primer will not adhere for long. Etch primer contains a light etching acid that bites the metal. Mix it at 1:1 with multipurpose thinners.

3. With your primer ready to go, Wipe done entire car with Prepsol. This stuff is a very diluted and gentle Hydrocarbon, gentle enough not to melt paint, strong enough to remove chemical contaminants. You can never Prepsol your car too much, you can never be to safe.

4. Tack Rag the whole car. The Tack Rag has a sticky resin on it that picks up any lint, dirt or dust. If you don't you will be sorry. It's not always possible to see every spec of dust so do a good job.

5. With your Etch Primer mixed, apply 2 coats. You must allow at least 5 minutes between coats, this is called flash off time. It is important to allow it to flash off between coats. For acrylic to cure, the solvents must evaporate, if you put it on too thick or too quickly, the solvents get trapped in and create little bubbles that become Pin holes when you sand. The ideal temperature for painting acrylic is 25-28 degrees. If it is cooler you need to leave it longer to flash off. If its only 20 degrees, you will need to leave it for about 15-20 min between coats. If it is more than 35 degrees don't paint. It will flash off too quickly and you will get pin holes. Despite common belief, it won't burn unless the car body is about 75 degrees or over. People mistake the solvent pinholes for heat bubbles. They are totally different. Leave for at least 3-4 hours

6. Ok time to mix your primer filler/surfacer. You are mixing it as Primer filler. That means that you only dilute it with 15-20% Multi Purpose Thinners. For primer surfacer you would mix it at maybe 50-70% thinners. The only difference is the mix. In days gone by, painters used to etch prime, then use primer surfacer, then spray putty to conceal fine scratches, then use primer surfacer to cover the spray putty, then guide coat, then put down the colour. What I am showing you is the modern and far more efficient but in no way a lesser quality method. We will use the primer surfacer for spray putty and surfacer. Apply 5 coats. Leave it a week to cure and shrink back properly, you can sand after a couple of hours but you will have problems.

7. Now it's time to guide coat. Mix up your black about 60% Acrylic thinners and 40% black. You only need to dust coat the car. The aim of a guide coat is not to paint the car black but to put down just enough to make the Grey primer just ONE SHADE DARKER. All you want is a little darker. It should only take 1-2 seconds to dry. With your hard block and 600 grit sand paper wet sand the car till all the orange peal and any visible scratches are gone it will not take long and it will be really easy to see when they are gone, you will have one consistent shade of light Grey. You may find that some places take longer. If you encounter one of these places in the middle of a flat panel or some where that doesn't make sense, you probably have a low spot, send it back to the panel shop. It may require bog or further beating.

8. So all guide coat is gone. Because we're doing this the new faster way, that's the end of your undercoating. If you managed to rub through all 245 microns of the primer filler that should have been on there, touch it up, but that is otherwise it for under coats, time for colour.

9. Mix up your colour as per the instructions on the can. Paint manufacturers vary in how much they require you to thin their paint, it can range from 50% thinners to 75%. The reason it varies is because straight paint already has thinners in it. The more that it already has, the less you need to add. The age of the paint will effect the amount of thinning it requires to. Just start by mixing a small amount of paint using their recommendation and add paint or thinners as required. For a good point of reference, the mix should be about as runny as full cream milk. Stir it till its all the same colour and consistency and then lift the stirrer out of the pot and watch the paint run off, it should do it and the same speed milk would. There is a correct method for measuring viscosity where you time how long it takes to drip, considering that the difference is purely academic just run with the milk analogy. I have never seen a painter measure it properly, they all just look at it running off the stirrer.

10. With your paint now ready to go, repeat steps 3and 4.

11. To test that the gun air/material ratio is good test it on some paper or something that isn't your car. To test it, start by getting your distance right. Holding the gun in you spraying hand, get your other hand and put your thumb on the fluid tip (the part the paint comes out of) and stretch your pinky finger out about ½"off the job. That is about the correct distance for spraying, a palm width. Now, on your gun you should have at least two control knobs, one to adjust the amount of paint and one to adjust the "fan". Wind the paint control and fan all the way in so that when you pull the trigger all that comes out is air. Moving the gun from left to right as though spraying, gradually increase the amount of paint flow until it just looks wet and not powdery. If it is too wet it will run, so make sure that it is only wet enough to stay glossy for a couple of moments but not so wet that it runs off. Now you may find that there is a lot of the material bouncing straight of your test piece and going in to the air as dust. That means the air pressure is to high, you may be able to adjust this on your gun but you may just need to turn it down at the regulator. For a conventional gun, you want about 30-35psi and for HVLP about 25-30. Now that your air is right you may need to tweak the paint adjustment again to get it right. Now, spray the gun in one spot holding it still for about 3 seconds. Look at the shape of it when it hits the job, you should have a small circle. Now wind the fan out until your circle starts to become a vertical oval, now turn the gun 90 degress so that the oval is horozontal, keep winding it out. You will see that when you wind it out all the way your oval becomes a pea nut and the paint runs more at the ends of the pea nut than the center. Start winding it in again until it becomes an oval again and the paint is dripping on the test piece evenly from one end of the pattern to the other.

12. With your gun now working and you panel prepsoled and tack ragged, you can start painting. Always plan how you're going to paint the car, e.g. don't paint the side and then try painting the roof because you'll end up leaning in the wet paint. Always do the roof first and start in the middle and work to the edge so that you aren’t leaning over wet paint. Same goes for any panel you need to lean over. As for everything else, start with your edges first making sure to get paint on both faces of the edge and then start filing it in. Start at the bottom of vertical panels and work your way to the top. Keep a constant distance from the job and keep you angles the same, don't swing the gun left to right otherwise you will have a thick build in the middle and a light one at the ends. Make sure you overlap each stroke 50%

13. After each coat allow the panel 5 min to flash off, remember more time when it's cooler. If you are using a solid colour, you will need to apply 5-7 coats depending on the level of finish you are after.

14. With your last coat you can do what's called a "flow coat". This is a different mixture that you still apply the same, it should provide instant gloss off the gun. The appeal of flow coating is that hard to get to places still get gloss on them, places that are hard to compound like door sills and engine bays. It is also much easier to compound a flow coat. To mix a follow coat for a solid colour, use 10% colour, 10% acrylic clear, 25% retarder thinners, and 55% acrylic thinners. This is a very runny mix and that is the intention as it will have a self leveling effect that’s highly glossy and almost flat (it will still have light orange peal but will look no worse than an average 2K job).

15. Leave paint to cure for at least 7 days before going to step 16.

16. You now need to compound the paint. This is the final stage, this is where we bring the paint up to a flat, high gloss.

17. Start using 1200grit paper and CLEAN water. You may want to get a CLEAN rag and wet it so you can use the rag to keep the panel wet. When you sand it is important to do so only with light pressure and that you pay attention to make sure that the paper isn't clogging or it will scratch the paint. It is also important that there are no jagged edges on the paper, they will also scratch. Try sanding in a circular motion until all the orange peel is gone and then sanding in a straight motion until all the circular scratches are gone. This way you will hardly notice any sanding scratches.

18. Depending on the level of finish you are after, you may wish to progress to a 1500 and then 2000 grit paper that ultra fine finish, but it is optional.

19. Once all the sanding is done its time to compound. If you are doing it by hand, dab a small amount onto a section of the panel and then spread it around, there should only barely be enough to cover the panel, there should not be so much that you can only see the colour of the cutting compound. Work it in a circular motion until a high gloss appears. Only do a small section at a time as it takes a while and the compound will leave funny marks if left too long. You do not need water if you are doing it by hand, it just makes it take longer.

20. If you are compounding by Machine... Once the sanding is done, apply compound to the panel as per step 19, and wet the buffing pad. You can use a lamb's wool or foam pad it’s a matter of preference… But I will say that I know for a fact that accredited BMW smash repairers have to use lambs wool not foam… any way, again work a small section at a time using a circular motion until a high gloss appears. It does not take a lot of pressure, usually the weight of the machine is all the pressure it needs, maybe a little bit more. Speed should only be about 300-500rpm. Excess speed or pressure may burn the paint.

21. Once all the compounding is complete wash the car with a car washing liquid that is a soap only, not a wash and wax in one type deal. It's important to remove all traces of the cutting compound. TIP use a paint brush to get the compond out from between panels etc.

23. With all previous products removed, its time to wax.. DO NOT WAX FOR AT LEAST 5 WEEKS FROM THE TIME THAT ALL SPRAYING WAS COMPLETE, otherwise the wax will trap the evaporating solvents and cause them to ruin the paint finish.
The idea of the wax is to seal the paint and stop it oxidizing and loosing is shine. All waxing should be done by hand. Just make sure that its silicone free, it should tell you on the packaging. The ideal one to go for is Carnuba wax (that is a type of wax not a brand). Just follow the directions on the bottle. One handy tip I will give you, after you have finished buffing the wax after it hazes, buff it another 2 times using clean dry cloths. It will shine even more and it won't smear as easy.

Display posts from previous:  Sort by  
Forum locked This topic is locked, you cannot edit posts or make further replies.  [ 1 post ] 

All times are UTC + 10 hours

Who is online

Users browsing this forum: No registered users and 2 guests

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  

© 2016 Ausmini. All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.