Tech articles about anything related to Eastwood Tools, Paints, and Chemicals.
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One of the big, time consuming jobs on any project vehicle (unless you are building one from scratch with raw sheet metal,) is stripping off years of old paint, primer, and anything else on the body panels. There are as many different ways to strip paint as there are types of paint to apply. Many times, especially with older projects, there may be multiple layers of primer, urethane, lacquer and enamels between the bare metal and the outside world.
Matt took an extra hood from a Chevrolet Monte Carlo that was a perfect example of this and used it to show the various mechanical, chemical and abrasive methods that Eastwood offers to take off old paints and primers. Here on the table you can see various sanding, grinding and other a mechanical methods to get the paint off the surface. Right by Matt’s elbow you can see several sizes of the Eastwood Gel Chemical Paint and Powder Remover. And on the right of the screen you can see the big blue tank of the Eastwood Abrasive Media Blaster, for spraying various grits of media at the panel that will eat the paint off.
Of course you always want to wear proper safety gear no matter what you are doing. Besides the normal dangers when you are grinding and sanding, working on old cars can expose you to lead paint and body solder, as well as rust and tetanus. You should at least have a pair of safety goggles on, and a filter over your nose and mouth to keep the dust out. A pair of sturdy leather gloves gives you something else to cut or burn before you get to your actual skin. When the particles really start flying, a clear fold down full face shield is a good idea as well.
Hand Sanding with a Block
This is the cheapest and easiest method, but that is only if you don’t value your time, or you are just looking for an upper body workout. Mister Miyagi had great luck with tricking local teenagers into doing this by promising to teach them karate.
The advantages of the paper and sanding block method are that there is very little to buy before you get started, it is gentle to the metal, and you can get into really tight, irregularly shaped areas. The main disadvantage is that it will take what seems like a year to sand off the old paint on the whole car. After 30 seconds of work, Matt barely was able to get through the top layer of black paint and down to the white.
Dual Action Sanding Disc
Next up is the same 80 grit sand paper, but this time spun by a dual action sander, sometimes called a DA or random orbital. This works very much the same as the hand sanding, only the air or electricity provides a lot of the work, instead of your arm, shoulder and back muscles.
As you can see, in the same 30 seconds the DA Sander was able to take off all the black paint, and in the one spot Matt focused on, three other layers to expose the base metal. The downsides of the DA method are you will burn through a lot of sand paper, you need a good air source, or an electric DA to keep up and do the whole car, and it’s really only suited for larger flat panels. The advantages over doing it by hand are obvious, but it’s not the best way to remove paint from a whole car.
4 1/2 in Flap Discs
The next item often used to remove old paint is the flap disc that attaches to your common angle grinder. It’s basically a flat disc with little pieces of sand paper glued to it in an overlapping pattern. All the edges of the paper give it a much more aggressive bite than just a flat disc like the one on the DA.
The problem is it’s usually too aggressive. Sure this tool will make short work of all the old paint, but if you aren’t careful it will leave a ton of gouges in the metal. Use too much pressure and it will even grind grooves in it. All this means more work after stripping with filler or high build primer to undo the damage you just caused taking off the paint. The flap disc is especially dangerous around edges and body lines as they can grind right through the metal. They do work great though for grinding and smoothing welds and surface rust.
Hook & Loop Cleaning Disc
Next up is the Eastwood Cleaning Disc, which is like a super heavy duty version of the green scrubby you use to clean pots and pans when washing the dishes. It’s available in a similar form to the flap disc, glued to a fiberglass backing for use with an angle grinder, but for big jobs it’s much easier to use the Eastwood hook and loop version. The hook and loop kit has a dedicated disc that screws onto your angle grinder, and cleaning discs that stick to it with a heavy duty version of Velcro. The discs are available in 80 grit and a 320 grit and are easy to change.
The woven material of these discs is great because it doesn’t come apart when you are using it and fling pieces everywhere. The flexible nature of the disc and backing pad make them much less dangerous to edges and body line too, and they don’t gouge if you push too hard. As you can see they make short work of blasting through all this old paint too. But if you use the disc in one place for too long it is possible to get the panel too hot and warp it, so keep moving.
Hook & Loop Stripping Disc
Next up is the less aggressive 320 grit hook and loop disc. This one does the same job it just takes more time. It’s less aggressive and more suited to taking off the clear coat and prepping a recent car with just 1 coat of paint on it.
As you can see it leaves a smoother finish, but it takes longer to cut though the paint. Eastwood sells a kit with both discs and the hook and loop attachment for your angle grinder. It’s great to start out with the more aggressive 80 disc, cut through the old layers of paint, then smooth it all out with the 320 disc.
Here’s a before and after on the same patch of hood we used the cleaning disc on originally, showing how you can use the stripping disc to finish the job and get down to smooth bare metal. Here is before.
And this is after.
3M Plastic Bristle Disc
Next is the plastic bristle disc from 3M. These bristles are very tough and come attached to a disc that screws onto a common 4 1/2 inch angle grinder. It works exactly the same as a wire wheel would, only the discs don’t fall apart as easily as wire wheels do and they are gentler on the metal.
As you can see, it’s a little more aggressive than the red stripping pad, but not as much as the hook and loop cleaning pad. And look at how smooth it leaves the metal after the paint is all gone! These bristle discs are very durable too and last a long time, so they are great for big jobs like a whole car. Be careful around edges though, because the bristles can catch an edge and get broken off, and they will hurt if they hit bare skin, so wear long sleeves and a face shield.
Roloc Quick Change Surface Conditioning Discs
These little discs are very similar to the hook and look stripping discs, only they mount differently and they are more flexible for sanding irregular surfaces. On the back on these discs is a little threaded stud that screws into a flexible rubber mandrel you can attach to any drill.
The softer, flexible nature of the mandrel allows you to use these for areas that aren’t flat. Also because these are so small, they are great for getting in tight areas like window frames and such. They are available in 2 and 3 inch sizes, and are commonly referred to as “cookies.”
That’s it for the mechanical methods of stripping old paint, but there are other ways to take off paint that don’t involve spinning discs.
Eastwood Paint & Powder Stripper
Guys often wonder about stripping paint off with chemicals. How well does it work? Is it safe for the panel? It is safe, and it works great, especially in areas that have tight curves or something that would prevent you from getting a cleaning disc or bristle disc in there.
You do need to wear rubber gloves though, because if you get this stuff on your bare skin it will burn.
Then it’s just a matter of brushing it on, use these acid brushes that are made of a plastic that won’t melt in the chemicals.
Wait 30 minutes or so and start scraping it off (Matt cheated and applied the stripper before the cameras started rolling so it would be ready now.)
As you can see the first application took off almost all the layers of paint. You could use mechanical means to strip the rest down to the metal, or apply the stripper again and you should have a totally clean bare metal surface. To make it even more effective, especially if dealing with modern clearcoat, use the DA sander to scratch through the surface first, then apply the stripper.
Finally, the last best method, and the most expensive to get set up to do, is media blasting. Media blasting sprays various small particles like ground glass, aluminum oxide, silicon carbide, and walnut shells, at the panel with high pressure air. For softer surfaces like fiberglass and urethane, soda blasting does the same thing with a softer media similar to baking soda. You do have to be careful though because media blasting can still warp a panel if you stay in one spot for too long and it gets hot. You also need to tailor the media to what you are stripping. Use too coarse of a media on a soft metal like aluminum or pot metal and you will be left with a rough surface that will take a ton of work to correct.
Eastwood offers big, pressurized media blast tanks that are great for doing entire cars, or blasting a frame and chassis if you are doing a frame off restoration.
If you don’t want to spend the money and make the commitment to a big set up like this, Eastwood also offers a Small Blast Kit that is very affordable, and great for doing just the problem areas of the body panels.
The best places to use the Small Blast Kit, or any media blasting really, are problem areas like these intricately shaped edges of the hood. There is no way you are getting a cleaning disc or wheel in there, which means you could be there for hours with a piece of sandpaper stripping the paint by hand. The media blaster will make short work of this.
Eastwood Fast Etch
Once you are down to bare metal, you need to make sure you protect it so it doesn’t rust immediately. Eastwood Fast Etch not only helps eat away minor surface rust and prep the bare metal for paint, it also leaves a protective phosphoric coating. The coating will protect it for a good long time, and can easily be wiped off with PRE painting prep with just a rag before painting.
If you do have surface rust on bare metal, you can spray the fast etch, let it work for a few minutes, then just wipe it off. Here is before.
And this is after. Obviously it could have used a few more minutes.
To use Fast Etch as a protective coating, just spray it on and leave it on. It will eat into the metal, then react to create that phosphoric protective coating.
So those are basically the most popular methods of removing paint and getting down to bare metal. Of course if you don’t want to do it all yourself you can always send the whole body out to be media blasted by a professional. There are also places with tanks of stripper so large a whole car can be submerged to eat away the paint and rust, but there is no way you are going to do something like that at home.Click Here To Read Full Post...
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How to Choose the Right Sanding Block
The sanding block gets its name because once upon a time it was just a block of wood with sandpaper stuck to it. The hard, flat block allowed you to sand to a much more uniform surface. Later, the heavy rubber style “alligator” or “vampire” sanding blocks were invented with teeth in them to grip a 1/4 strip of sand paper, but that compared to today that is still stone age technology. Now there are blocks of all shapes, sizes and materials, for use on different shaped panels, and make all of our lives easier.
Sandpaper has come a long way too, but nothing much has changed about how you use it. It’s just formulated with different abrasives, glues and backing to cut faster, longer and not fall apart. There are also neat innovations like adhesive backs and hook and loop attachment. But even with the advances since the 1980s, it’s pretty much the same process Daniel used in Karate Kid, back and forth, back and forth, until you build up the muscle memory to defend yourself, or block sand a car. Remember, when sanding with a block use alternating, crisscross strokes, and always push the broader edge of the sanding block as the leading edge, not the narrow one.
If you need more information of block sanding and body work, the Eastwood YouTube channel and Tech Library are full of helpful how to stuff. Kevin Tetz has done quite a few videos demonstrating exactly how to do body work and prep for paint. According to his expert opinion, any paper with a grit coarser than 220 is for shaping, and finer than 220 is for sanding.
Shaping is what you do to grind down welds, smooth body filler, and remove tiny waves from the metal work. Often times you are staring with something like 36 or 40 grit to grind down patch panel seams or body filler. Gradually you get finer and use something like 200 grit to shape high build primer before applying a sealer, and starting to paint.
Sanding is what you do to promote adhesion of the next coat of paint to an old coat that is beyond the time window where it will chemically bond. Sanding is also what you do to get rid of paint imperfections like orange peel and drips. You can and will use sanding blocks at both of these stages, but they are different types.
Rigid - Typically when doing initial shaping you will be using a very coarse paper, and a hard block, or even some sort of power tool, depending on what you are shaping. No one needs an explanation of how to grind a welded seam of a patch panel down with an angle grinder. Once you are beyond that stage though, you likely will be using a rigid block.
This block is really the least advanced and can still be a hunk of 2 x 4 cut the size of your hand with adhesive backed paper stuck to it. For more advanced options try the 2 handed Eastwood Contour Rigid Sanding Board (#31056 or #31057), Dura-Blocks (#31160 7 piece kit, or sold separately), or the Adjustable Flexible Sanders (#20326) with all their stiffening rods in place. You can even make your own blocks to fit in unusually contours, or tight spaces out of a piece of dowel, a paint stirrer stick, or anything handy.
Shaped - If you are doing a repair on a surface that crosses over a body style line, or is a concave panel, you’ll want to find a shape that matches it as closely as possible. This helps you get an accurately shaped repair without a lot of artistry and free hand sculpting. This is where making your own sanding block is useful.
Eastwood has lots of different types of these, including soft blocks that can be shaped to your will for sanding large contoured areas. Again Dura-Block makes a great kit (#20553) including round, and teardrop profile nearly rigid blocks, the Style Line Soft Sanders kits (#12555 or #19311) include different rigidity, and a wide range of profiles for most any part that needs sanding.
Semi-Rigid – Semi-rigid blocks are prefect for fine shaping, contouring, and curved, crowned surfaces. Let’s face it we talk a lot about body panels being straight and flat, but even on a boxy Volvo, there are subtle curves stamped into every body panel. In order to properly smooth and shape these you need semi-rigid blocks after the initial shaping has been done.
A great tool for this is the Adjustable Flexible Sanders (#20326) with the removable rods, because you can start with them full hard for flatter areas, then make them less rigid as needed. To make short work of large areas try the 2 handed Eastwood Contour Flexible Board Sander (#31007). Then there are the palm sized Semi-Rigid Sanding Blocks (#34046) for smaller detail areas.
Flexible – The final shaping you do, and most of the block sanding of paint imperfections, is going to be done with more flexible blocks. It just makes sense. The softer and more flexible a block is the less aggressive it is going to cut into the surface of what you are sanding.
The Adjustable Flexible Sanders (#20326) with no rods in them are good for this, if you are doing a large area at once. Otherwise the Flexible Sanding Blocks (#34055) are great, or even the softer side of the Semi-Rigid Sanding Blocks (#34046) is it’s a relatively flat panel you are shaping.
Block Sanding Paint
Funny that many people when they think about block sanding are thinking about this step. Block sanding paint happens after the paint and primer are all done and you are just fixing the final imperfections and getting the mirror smooth gloss. This type of block sanding doesn’t really need all the various blocks at all. A simple semi-rigid, or flexible pad is really all you need. For larger flat areas even the old fashioned rubber palm block will work. Or use the more modern version of that old stand by the 6” Flexibility Palm Sander (#31171)Click Here To Read Full Post...
Hopefully this little run down of sanding blocks and their proper use has helped you out. Of course if you have any questions you can find answers in our tech library, our online restoration forums, or our help line. The Eastwood YouTube channel is also full of helpful videos showing how to use the products we sell, and how to do just about anything when it comes to body work.