Autobody 101 Part II

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addo

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Following from Phil's topic, here's some more "FAQ's"

Question: How much might it cost to paint my car?

This is impossible to answer generally, yet is a frequent enough question! Bear in mind the following (in approximate order)

  1. Initial condition of the car. If you start with a rusty or damaged car, then obviously it’s going to need bodywork at the going shop rates. Sure, you can try yourself. Remember that topcoat paint is often less than the thickness of tissue paper, so your “foundationâ€￾ work better be good. Also beware of the car that looks good on first inspection. Closer up, all the seams may be rusted and there’s a lot of remedial work needed if a repaint is to endure. More work, more money. Also, stuff can be so deteriorated on the car that when it’s removed to prepare, it won’t go back on without work.
  2. Present colour vs Finished colour. This is more self-evident. A nice repaint job does all the internal details and spaces – inside the engine bay and luggage areas, door edges… Time taken to prepare all these areas is staggering until you realise they add up to a lot of extra surface are, and are frequently dirty, damaged or neglected to begin with.
  3. Quality sought. “You get what you pay forâ€￾ never loses validity. There’s no free lunches in the autobody business. The people who get decent jobs from “budgetâ€￾ outlets usually start with a good car, do a substantial amount of pre-prep themselves, pay for the premium quality paint offered and have sometimes been known to “induceâ€￾ the employees with a few dollars out the sight of management. Be realistic in your expectations. It’s better than having to be realistic later down the track.
  4. Location of car – shop rates vary so much by area, you should only rely on local prices to you. Their prices reflect what customers will tolerate, the shop’s hired labour skill content and costs, premises and equipment. Sometimes it can be cheaper to ship a car out for work, if you have a confident level of rapport with the business contracted to perform the work. If you just shop locally, might miss out on some savings.
  5. Level of competent owner input. Another detail where people can get ahead in their refinish budget. If you’re confident to not just wash a car top to bottom and degrease, but remove, clean and store parts for refitting (don’t leave the cleaning until after), you’ll save the shop staff, and your money for better tasks.
Question: If I do the bodywork and primer, how much might it cost to paint my car?

See the question above on painting your car! There are a lot of variables. So many that this is not a recommended method unless you’re looking for a functional-grade paintjob only. Once again, the repairs, filler and primer are the foundation upon which a successful topcoat is laid. Possibly, if a bodyshop is kind enough to teach you the basics of wet sanding a properly applied primer, you can save a day’s labour for two guys, by spending a week or two doing it yourself after hours. Note that after wet sanding, the car should be painted before exposure to weather or any use.

Question: OK then, think I want to paint my own car! How hard is it to do?

It’s not easy. Bodywork courses typically have up to 1000 hours of training at college, plus equal or greater shop hours required before qualification. If you put in 2500 hours on your car’s paintwork, you’d be reasonably entitled to feel experienced. Typical problem areas include:

Lack of basic hand skills and endurance/perseverance
Woefully inadequate tools
Inappropriate work space (do consider others!)
Failure to consider occupational HEALTH ISSUES
Poorly planned course of action
Insufficient budget to complete the task

The best way around these is Planning, with a capital P. There are stories of people who’ve attended a community college hobby course or similar, gained a little experience and insight, and then been able to walk the line to get a result they can live comfortably with. You’ll find these types are capable of planning a little. Even when a plan goes awry, you are able to backtrack and analyse its failure points. No plan=no idea.

Question: What tools and materials are involved in preparing a car for paint?

What a list! Firstly, your safety gear. Eye, ear and breathing protection. Whenever you’re working with chemicals, READ THE LABEL FIRST. Now, in no order:

  1. Dual-action sander (aka random orbit sander or “whizzerâ€￾). This will go well with coarse paper to remove a lot of paint. Air powered is best – more grunt.
  2. Grinder with twist-knot wire brushes. Choose the brush styles you like and can use. The flying broken wires will embed in your flesh. Trust me. Grinding discs are good, too.
  3. Die grinder with assorted grinding, cutting and wirebrushing attachments. You will be surprised where this will go with its small size and the flexibility of a wire brush.
  4. Electric drill – large, corded.
  5. Small cordless drill.
  6. Heat gun – often handy for persuading stuff to come apart or off.
  7. Scrapers and chisels for hard to reach areas, and cleaning up after paint stripper.
  8. Files, sanding blocks, assorted sandpaper. Again, different people have different methods. Common is a few rough files for smoothing stuff out (including filler), a “speed fileâ€￾ or strip sandpaper holder, couple of different size rubber hard blocks, also soft foam backing pads
  9. Sanding sponges, Scotchbrite red and grey, white sandpaper from P60 through P220, and wet & dry ranged from P400-P800.
  10. Paint stripper of a recommended type is often a real timesaver and dust minimiser. Read its directions carefully, including details of any neutralisation process required. Most are not recommended to be used in seams of panels.
  11. Media blasting is popular for detail parts cleanup and may save some time. It requires a compressor capable of airflow to meet the blaster’s needs. There are safety hazards with blasting, such as dust and debris, that should be fully guarded against.
  12. Priming and filling materials – see other “101â€￾ topics.
  13. Masking tapes, brown paper, wax and grease remover, acetone for stubborn contamination, rust conversion agents. Quality is reflected in the price. Cheap tapes will either fall off or leave residue. I don’t trust wax and grease remover of the cheap brands to be water free, nor cheap acetone. Use a rust conversion recommended by the maker of your primer, and follow the paint maker’s directions where they may differ from the rust converter label.
Question: What should I take off the car when painting?

The bare minimum when repainting in the same (or very close) colour is front and rear bumpers, grille and trim, badges/emblems, chrome trim strips, hubcaps, all lights and their trim, trim around glass, door outer handles, door mirrors, outer weatherstrips on side windows. This is all assuming no repair has been needed and prep work is minor. If more has to be removed for the purpose of prior repair, the better. Ugly outcomes include overspray on headliners, wiring harnesses and underbody, so ensure these areas are appropriately protected. The budget approach of masking around stuff is bound to come out looking like a budget job! If you have removed whole panels for painting, often it is best to paint the edges and undersides first, then mount again and spray the outer as a whole. When reassembling, remember to consult the notes you took on panel gaps, order of washers, types of screw used and so forth. A digital camera may be a fine asset, but especially so in conjunction with a notepad. Don’t be too surprised if the new paint makes the parts removed prior, look a little shabby!

Question: Spraying paint – what equipment is needed?

A short, snappy and useless answer would be “more than you thinkâ€￾. Just for the spraying process, ignoring all the preparatory tools such as air sanders, the list is basically:
  • Compressor – check your cfm at spraying pressure. This is way different from free air cfm – the rating manufacturers like to show. For high pressure work, you need 8½ cfm minimum. With a decent size receiver (tank) on the unit. HVLP will require more cfm, and often a compressor with somewhat different operating characteristics.
  • Regulator – The combined trap/regulator is a good buy. I suggest one size up from your air lines. If you run air hose with 3/8â€￾ internal diameter (ID), then get a regulator with ½â€￾ internal fittings. The regulator should be mounted uphill and a good way from the compressor. Compressed air can carry water vapour in suspension if it is warm. Making it run uphill and have time to cool off, causes some of the moisture to drain back into the compressor tank where it can be let out later. The regulator gauge should be a decent quality. A pro shop will have a refrigerated air drier at this stage, too.
  • Air lines – these need to be longer than you think! 60 feet from the wall outlet adjacent to the regulator, in the spraying area, is good. The hose couplings should be a high-flow type, typically with steel fittings for improved wear. Use an appropriate chemical resistant hose; it should be clean outside (especially from contaminants like greases or silicone), and never been used with “oiledâ€￾ air lines, as they will coat the insides of the hose.
  • Blow nozzle – You will always use a couple of these. They also get trodden on and broken (don’t ask me why; everyone seems to do this now and then!). Make a hook of wire to hang it out of harm’s way the rest of the time. Good quality blowers have a nice smooth progressive trigger action and non-corroding internal parts.
  • Moisture filter – This should be as close to the final “runâ€￾ of hose as possible. It will trap the last microscopic droplets of water and oil in the spray air, possibly making it safe for breathing. Check with the manufacturer, such as Motorguard. NEVER breathe regular unfiltered compressor air. It contains oil particles which may cause illness such as pneumonia. Remember that the filter will obstruct flow and reduce pressure a little, and that elements need to be replaced regularly at some non-trivial cost.
  • Spraygun – these are almost like underwear; everyone has a slightly different preference and feels uncomfortable with another person’s “rigâ€￾. HVLP has a large following but you need to be set up for it with the correct sizes of hose, and flow rate of compressor/filter. Good old-fashioned high pressure setups are frequently the best for amateur use. You NEED a gravity gun no matter which type. They waste less paint, clean up faster, and can be had cheap with a couple of different size nozzles. Not everyone needs a SATA or IWATA gun. A decent gun will have pressure regulation on the handpiece, control of paint volume and pattern width, as well as trigger pull, and can be fitted with a gauge to show incoming pressure. Some people in humid environments put a “last chanceâ€￾ disposable air filter canister on the gun as well. For a gravity gun at high pressure spraying primer/surfacer, a 1.8-2.0mm nozzle is recommended. Topcoats in urethane or air dry acrylic go well with a 1.5-1.6mm nozzle. Nothing beats practice to gain “marksmanshipâ€￾ dialling your gun into your environment and materials.
  • Fashion – you want to keep dust to a minimum so disposable hooded coveralls are a good move. These are readily available and often seem to turn up NIB at swap meets!
  • Safety – Pollutants may enter through your skin, eyes and airways. That is why pro painters wear a full face setup which restricts these possibilities. If you choose to paint your own car, you should use one of these with its dedicated breathable air supply line. Should you just decide to wear goggles and a mask, be aware that this is not fully safe, and you have been warned here! Remember; live long enough to inconvenience your children in return…
Question: How do I buff/polish paint, old or new, for better appearance?

Buffing is an illusory activity. It’s about hiding or replacing big scratches with lots of little scratches.

The first determinant is the durability of the surface under polishing. Is it new and soft, old and thin? You can burn through either of these types easily with overzealous mechanical polishing or pre-sanding. A lightly aged intact finish is the easiest to deal with. All the types may require initial topical repairs, the lightest touch of wet sanding here or there with ultrafine paper, then follow a buffing compound system – 3M, Meguiars, Farécla from one end to the other. Try the finer grades to start with. Firstly it can save you money on these materials, which in pro brands and quantities aren’t cheap, and secondly, it will erode less paint. All systems will work by hand, although some discourage it with the coarser compounds as marks are difficult to remove with hand polishing.

A proper rotary buff with a variety of pads recommended by the compound manufacturer will get you started. The lambswool pad on a drill shaft is a poor substitute. Often, you will have to detail small areas by hand or seek out alternative means of reaching them with a rotary tool to polish. Some people now prefer a random orbit buffer for the final “glazingâ€￾ of the surface. Again, industrial products are rated much better than home style ones, so do not expect otherwise in performance. Always follow the manufacturer’s recommendations for application, including temperature and sunlight exposure. Again, observe SAFETY.

That's about it for now! I've got some thoughts on rust repair, too, but they can wait. The topic is locked, so relevant questions can be posted separately without diluting the FAQ content.

Thanks, Adam.
 
Thank you so much! I think I'll print this out and send it to all potential customers.

Thanks,
Jon
 
Two great postings. Just what I needed when I needed it. Could I make a request. Could you discuss what (and maybe how) to do to get a car as ready as possible to take to a painter? You have covered what to take off but how about things like wet and dry sanding, chemical (?)cleaning the surface, etc. I sure it would really be appreciated.

Thanks,
Tomtron
 
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