Stripping paint
From Crankshaft Coalition Wiki
(New page: Although it is possible to paint over old paint, you may choose to get rid of it. This might be because the paint is cracked or peeling, or that there are already too many layers of paint ...) |
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==Inspecting the panel before stripping== | ==Inspecting the panel before stripping== | ||
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==Methods of stripping paint== | ==Methods of stripping paint== | ||
===Chemical=== | ===Chemical=== | ||
| − | There | + | There are a few effective brands of chemicals for stripping paint from vehicles. However, this practice may be inappropriate for novices, as these strippers are messy unless you know a few basic techniques. They can also be acidic and toxic, so wear gloves. |
| − | First, take the vehicle or part to be stripped to a well-ventilated area (outside is ideal). | + | First, take the vehicle or part to be stripped to a well-ventilated area (outside is ideal). ''(Should a respirator be used? Some people are saying that makes it even worse.)'' |
| − | These chemical strippers are more commonly used on hoods, roofs, and trunk lids as they need to be left alone after applying. | + | These chemical strippers are more commonly used on hoods, roofs, and trunk lids as they need to be left alone after applying. some strippers would just run if put on a vertical panel, and thus would be somewhat ineffective. So, find one with the viscosity of mayonnaise, and use tar paper on floor where paint can fall; this makes cleanup much easier |
| − | + | All areas besides the areas you want to strip should be properly masked or removed. Stripper could seep behind a molding and be problematic later. Stripper will damage plastic lenses. | |
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| − | + | After paint has lifted, scoop it up with a putty knife or credit card, and discard the paint/stripper mixture into a cardboard box. Don't get any on your skin -- it burns. If you do, wash it off IMMEDIATELY with water. | |
| − | + | Once you've scooped up most of the mixture, wash off the rest with lacquer thinner and a red scuff pad. It will dilute the stripper and render it less volatile. Then, pull off the three layers of tape covering the gaps; the paint underneth will be softened up just scrape it up with a razor scraper. | |
| − | + | Wipe underneath the hood or trunk before reaching under it. Stripper will surely have seeped there and leave you with a nasty surprise if you don't seal the gaps with tape. | |
| − | + | After the area has been washed off, wipe it dry with a clean cloth and wax & grease remover. Remove any remaining paint or primer with an orbital sander using 40 to 80 grit. See [[Stripping paint#Orbital sander|Orbital sander]] below. Always use gloves when working with bare metal -- the oils in your hands will instantly start the rusting process, even under the primer. | |
| − | + | ====Lacquer paint==== | |
| + | When used on lacquer paint, chemical stripper will run and make a big mess. You should be ready to catch it with masking paper taped to the car, and by pushing the soupy paint onto the paper and pulling the paper off as you go and throwing it away. Lacquer paint can be stripped by soaking clean rags in lacquer thinner, applying them to the vehicle, and then leaving them there a while in a well-ventilated area. Covering the rags with plastic also helps, and keeps the thinner from evaporating too quickly. You can scrape the softened paint off with a razor scraper. | ||
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| + | ====Stripping a roof==== | ||
| + | Surrounding areas should be properly masked with several layers of tape and masking paper, as stripper will work its way through tape glue. Just scrape the mess onto one layer of paper and pull it off; the sheet underneth will be ready when its needed. | ||
| − | === | + | ====Stripping a hood==== |
| − | + | Pop the hood and slip lengths of cardboard half a foot underneath it, all around the perimeter. Or, put three layers of 3/4" masking tape over the gaps so the stripper doesn't get down into engine compartment. Close the hood tightly. | |
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| − | + | ====Stripping a trunk==== | |
| + | Same as hood. Tie weight to the latch to keep the trunk from rising, or tape with the same three layers and close the deck tightly -- the three layers of masking paper at the back edge of the deck and push the mess onto the paper then pull the layer off and throw in trash. | ||
| − | + | ====Chemical paint strippers==== | |
| + | *Aircraft stripper (blue can) | ||
| + | *XXX paint stripper (black can with red X's) | ||
| + | ===Mechanical=== | ||
| + | ====Razor blade scraper==== | ||
| + | There are instances where using a 4" flooring razor blade scraper or smaller razor scrapers made for body and paint work will be the quickest way to remove a layer of paint. However, if the paint has properly adhered to the primer, using the blade might not be possible. Once paint has been removed, you may want to remove the rest of primer and areas of paint that were not possible to remove with the blade . | ||
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| + | *Never start off with a used blade -- nicks will scratch deeply in the metal. As soon as you get a dig, change the blade. | ||
| + | *Try using straight back blades for body work. | ||
| + | *If the ends of the blade are rounded (slightly) from use it will keep you from gouging the metal. An excellent way to start is by rubbing the new blade quickly back and forth over glass like you're trying to scrape off overspray; this removes small burrs in new blades. To lessen any further risk of gouging, run the blade backwards against old smooth paint 4-5 times. This will push up the burr and permit the blade's edge to glide much more easily. | ||
| + | *You will have to pay attention to the way the body curves. | ||
| + | *Use two hands and steady amount of pressure & the paint will fly off in tiny little chips. | ||
| + | *Keeping the proper angle to the surface is critical. | ||
| + | *It seems that if you try not to take too big of a bite and try to make b "C" shapes or curves, it lets the paint come off easier. | ||
| + | *You will need to use both sides of the blade by switching sides often. This keeps the blade from getting too dull to get under the paint. | ||
| + | *Gloves, eye protection, and dust mask are mandatory. Little slivers of paint will go everywhere. A shop-vac while working is great for the cleanup. | ||
| + | *You may find that a conventional razor blade holder is difficult to use for stripping paint. The flakes tend to bunch up between the blade and the tool. To solve this problem, us a regular vise grip to hold the razor blade. Turn the vise grip upside down for a less dramatic angle of attack. Too sharp an attack might cause the blade to catch, which could gouge the sheet metal. | ||
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| + | ====Homemade scraping tool==== | ||
| + | Start with a stiff putty knife or drywall tool. Round the corners, then re-sharpen on a belt sander. Only sharpen one side, not both, then on a knife sharpening stone. Hold the knife with both hands, at a 90-degree angle to the surface. Start to scrape, and adjust the angle until you get the best results. As it wears, you can resharpen the blade with a DA sander: 80-180-320. that'll get it razor sharp again. | ||
====Media blasting==== | ====Media blasting==== | ||
| − | + | See [[Media blasting]]. | |
| − | + | Blasting with media that removes rust is one way to ensure the rust is removed from the bottom of the pits. Contrary to what the advertising would tell you, most chemical methods do not fully remove the rust from the bottom of a pit. Sanding to the bottom of a pit is likely to warp the panel through heat and the fact you are making the metal thinner. | |
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| − | + | Warpage of the metal is a common worry, but not an issue if one understands how and why the metal warps. The metal warps because of expansion of the surface of the metal from the impact of particles -- impingement. A small amount of impact will not cause enough damage to do anything more then make the surface a little bit rough. When the media is given enough energy through speed or density (faster or heavier hammers) then you will get the surface expansion that causes warpage. | |
| − | ===Methods of NOT stripping paint | + | To blast safely you need to run a low pressure and limit the amount of media in the stream of air. This will mean a much slower removal of material, but no chance of panel damage. One setting that has worked is 40 PSI on the pressure pot blaster and open the media valve just enough to see the sand mixing in the air. This setting will not damage the metal even with prolonged working in one area. |
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| + | The siphon blasters are more likely to cause warpage. This is because you can not easily regulate the amount of media in the stream. | ||
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| + | Keep in mind more significant more panel warpage is done while trying to repair a panel. See [[Sandblasting]]. | ||
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| + | ====Soda blasting==== | ||
| + | See [[Soda blasting]]. | ||
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| + | ====Sanding==== | ||
| + | See [[Sanding]]. | ||
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| + | Always use a respirator when using sanding tools. | ||
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| + | Removing paint from a panel using a random orbit sander is the least messy way of stripping paint from large panel. Use 40 grit sandpaper for the quickest job. | ||
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| + | After sanding off all traces of paint and primer, sand the surface smooth with 80 grit on the random orbital sander to smooth out 40 grit sand scratches, as they will show though the finish. Remove dust with a blow gun and a clean cloth. Don't touch the metal with your skin; it will contaminate it. Immediately spray on etching primer to keep ambient moisture from contaminating the panel. Always wear a respirator when spraying etching primer. | ||
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| + | =====Orbital sander safety===== | ||
| + | Prolonged use of orbital sanders can cause a condition known as "Vibration White Finger", or "Hand Arm Vibration Syndrome". For more details, see [[Health and Safety in the Shop or Garage#Vibration protection|Vibration protection]]. | ||
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| + | Commercial shops tend to use a hook and loop 80 grit pad on a larger sander. Several shops who participate on forums have commented that they have found this method to be the most economical in time and materials after trying all other methods. | ||
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| + | Bear in mind that paints on cars may contain lead. | ||
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| + | ====Wire cup brush==== | ||
| + | A wire cup brush will take paint off rapidly, almost as fast as 40 grit sandpaper on an orbital sander, when the wheel is mounted on an angle grinder. The wire wheel will not scratch the metal as deeply as the sandpaper, making prepping for primer a bit easier. | ||
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| + | Wire cup brushes come in two basic types - with kinked wires, and with twisted (or knotted) wires. Although it seems like the twisted wire would be faster, as it is more agressive, the kinked wire actually will strip faster, as it is more flexible and can make contact with a larger area of the panel with every pass of the tool. | ||
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| + | Wires will come loose and fly off the wheel during use. It is recommended to wear a face shield and thick clothing when working with one to avoid injury. | ||
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| + | ===Infrared paint strippers=== | ||
| + | ''(Is this a viable method for automotive work?)'' | ||
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| + | ===Crud removal air tools=== | ||
| + | Like a pneumatic angle grinder, but designed for rotary stripping discs. Used for removing seam sealers, [[rust]], paint, and underbody coatings. Used with an eraser wheel for pinstripe and [[Removing decals|decal removal]]. | ||
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| + | *[http://buy1.snapon.com/catalog/item.asp?P65=yes&tool=all&item_ID=76499&group_ID=13078&store=snapon-store&dir=catalog SnapOn PT280THUGA Air Removal Tool], [http://www.snapon.com/international/21pdffiles/pt280thug.pdf Info sheet] -- also known as the "Crud Thug". | ||
| + | *[http://www.tptools.com/p/1385,221_The-Stripper-Air-Operated-Rust-and-Paint-Remover-Kit.html "The Stripper", from TP Tools & Equipment] | ||
| + | *[http://www.autobodysupplies.com/MBXBlasterTools&Accessories.htm MBX Blaster] | ||
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| + | ===Other methods=== | ||
| + | If the paint is brittle when you chip it off, it could be acrylic urethane. If so, try using a heat gun. You might be able to peel the paint off after applying a little heat. | ||
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| + | Peeling paint can be removed with a high pressure pressure washer., be careful, you can damage plastic parts. Northern tool makes a wet blaster that you hook up to the pressure washer to wet sandblast, no dust but it makes a mess. | ||
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| + | ==Methods of NOT stripping paint== | ||
Using an angle grinder is not a recommended way of getting rid of paint. The grit is too coarse and will damage the metal and would require some type of body filler: extra work you really don't want or need to get into. | Using an angle grinder is not a recommended way of getting rid of paint. The grit is too coarse and will damage the metal and would require some type of body filler: extra work you really don't want or need to get into. | ||
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| + | ==Supplies== | ||
| + | *[http://www.tcpglobal.com/autobodydepot/paintremove.aspx Paint stripping tools and products from TCPGlobal.com] | ||
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| + | [[Category:Body and exterior]] | ||
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