Bondo Dent Puller How To Use

There is non a more maligned automotive product than "bondo". Plastic body filler is most oftentimes referred to past the brand name "Bondo" (made by 3M), and its bad reputation comes from decades of poor awarding and misuse. Virtually every high-end custom automobile or restoration has some amount torso filler on it. Using it on your daily driver or project is non a bad thing, every bit long equally you lot employ information technology the right mode. Learning how to use Bondo the correct way isn't equally hard equally you retrieve.

History of Bondo

Like most plastic torso fillers, Bondo is a lightweight polyester-based plastic body filler that was originally adult as an alternative to lead body solder. Old school body store techs used to cook strips of lead with a torch to make full torso imperfections and joints. The Bondo brand name was created in 1955 by Robert M. Spink, just a few years after the use of lead body solder began to be prohibited. Many bodyshop men of that age were not sold on the idea of using plastic body fillers, but over time, it became apparent that the lightweight, easy to apply nature of body filler was a benefit over atomic number 82. Not to mention that lead body solder is very dangerous to work with given the need for a torch to rut it, lead fumes, and even lead grit from sanding. In comparison to working with molten lead using plastic body filler just made sense.

Bondo Abuse

Where the bad reputation comes from is misuse and incorrect application. Nosotros've probably all seen a machine in the parking lot that looked like someone slathered on body filler with a trowel. Don't do that. Plastic body fillers are intended for small dings and smoothing out warped panels, not a major repair itself. It was never intended to fill up large dents, rust, or other major body damage. It does not move or or behave similar a metal body panel. Why would y'all waste product time laying down a gorgeous paint chore if you know the gigantic blob of plastic body filler behind it could actually pop off in the future?

You can actually check whether a automobile has besides much body filler by using a refrigerator magnet. Put a slice of newspaper between the steel torso panel and the magnet (to protect the paint), then see if the magnet sticks to the car. If a magnet won't stick to a steel body console, information technology may be loaded with plastic torso filler.

rust damage — Poorly applied trunk filler might work in the brusk run, just somewhen, it causes way more problems down the road.

Working With Bondo The Right Way

Now that y'all know a little more than nigh plastic body filler, yous can beginning working with information technology the right fashion. But there are a few key points that you lot should know before working with trunk filler:

Thickness Matters

There is no minimum thickness for Bondo, only there is absolutely a maximum. You practise non want to utilise trunk filler to anything that is thicker than about a 1/iv". That does not mean it can't be done, only the repair will not last every bit long. Eventually the filler will shrink and possibly crack, or fifty-fifty pop off! The general rule of thumb is that if the dent information technology deeper than 1/8" you need to do metal work first. Remember, your nice pigment job depends on a solid foundation. Simply troweling on the filler may look like the easy button, but that slab of filler may determine to fall off some solar day (we've seen it happen).

Fix The Foundation

What you are working with needs to exist properly prepped Earlier you apply any body filler. Do not slap Bondo onto a polish painted surface, it is not going to stick very well. The paint should exist sanded off, to the bare metal, and so apply the filler. A 36-grit to 180-grit surface is ideal for body filler application and so that the filler has a good rough surface to grip.

Not For Every Location

Don't use body filler on full gas tanks, or anywhere that gets hot. Bondo is resistant to fuel, but only later it is cured. If yous are smoothing out a gas tank, that is groovy, information technology y'all are trying to fix a rusted out gas tank, this is non going to do a good job. Don't misfile Bondo with JB Weld, the 2 are not the same.

It Won't Magically Fix Rust

Body filler is non good for rust repairs. You lot cannot slather some Bondo over rust and expect information technology to end the rust or stick to it for that matter. For rust repairs, y'all must first remove any rust scale from the metal. If in that location are holes in the metallic, you lot are much ameliorate off cutting it all out, patching it with new metal, and then working the body filler from there. Whatever rust left under the filler will continue to abound, so don't be surprised if a small repair turns into a bigger problem down the road. If you absolutely must use trunk filler to brand the repair, and so you lot should remove all the rust scale, add a backup screen to cover the holes from the back side, then use Bondo Bondo-Drinking glass over the rusted area, sand and finish out with regular Bondo trunk filler for a stronger repair.

Pay Attention To The Mixing Ratio

The mix is crucial. Most of this comes from feel, but you lot can get close to the optimum mix with this tip- use 1:1 ratio of inch diameter of filler to inch-length of hardener. A iv-inch diameter of raw filler needs a 4-inch ribbon of hardener at room temperature. If information technology is hotter (above 85 degrees), use slightly less, if is colder (below 65 degrees), utilise slightly more. If your filler hardens too fast, you used also much, if it takes too long, yous didn't use enough. You only want to mix what you can use in most 10 minutes. Properly mixed, body filler will begin to thicken in ten-xv minutes, and be fully cured in 30. Until y'all go the hang of mixing information technology is wise to purchase a bit more than plastic body filler than your project needs so you have room to endeavor again without running back to the store.

The general rule is to add a line of hardener across the diameter of the filler pool. This will get you pretty close at room temp. — The general rule is to add together a line of hardener across the diameter of the filler pool. This will get you pretty close at room temp.

Exercise not whip the body filler while mixing it. This will incorporate a lot of bubbles in the filler, which means more than pinholes to prepare subsequently. Apply a slow and deliberate effigy-X pattern, wiping the filler across itself.

Slowly pull the filler across itself to mix it in an X pattern. This will reduce the air pockets, which become pinholes in your body work. — Slowly pull the filler across itself to mix information technology in an 10 blueprint. This will reduce the air pockets, which become pinholes in your torso piece of work.

Application Technique Is Key

You lot can apply plastic or metal spreaders, choice is upwards to your personal preference. Metal spreaders last longer and provide a more than divers edge, but plastic spreaders are inexpensive and tin be custom cutting to lucifer shapes. Use the filler to the panel, pushing the filler into any crevices. Wipe the filler as smooth and level equally possible, just exit plenty of actress filler to a higher place the surface level to sand the repair smooth. Better to have a little likewise much filler and sand it off, than take to mix upwards some other batch of filler for a low spot.

Apply the plastic body filler to a cleaned and prepped surface using a metal or plastic spreader. Always cover a larger area than just the dent for feathering. — Apply the plastic body filler to a cleaned and prepped surface using a metal or plastic spreader. Always encompass a larger surface area than simply the dent for feathering. The goal is to blend the repair in smoothly.

This dent is about the size of a quarter in diameter, but the filler patch is 4x4. Most of it will end up on the ground. — This dent is virtually the size of a quarter in diameter, simply the filler patch is 4″x4″. Nigh of information technology will stop upwardly on the footing.

Go Ready To Sand…A Lot

At that place are two schools of thought on when to sand filler. If you are doing general bodywork, leveling wavy panels, fixing small dings, etc, so wait until the filler is fully cured, about 20-30 minutes. If you are using a lot of filler or doing some shaping with the filler, y'all tin utilise 36-grit sandpaper when the filler is in the "green" stage, this is solid, slightly rubbery, but not fully hardened. Using low-cal pressure, you can knock off large amounts of filler to rough-in the shape needed before the filler hardens, making sanding more labor-intensive. And don't forget the respirator and safety spectacles, fine filler dust tend to get everywhere when sanding.

The key to a quality body console repair is seamless filler work. The edges of the filler should feather out to the existing panel. Y'all should non be able to feel where the metal stops and the filler begins. Any defect you come across or feel in the filler volition exist amplified when the pigment is on the body, and so check the panel repeatedly. Large repairs require extra try, equally y'all can hands become waves and ripples in the bodywork when working a large area. Never sand in straight lines, instead utilise a criss-cross pattern, up and down, side to side. This eliminates waves and results in a much ameliorate repair.

Always use an X pattern to sand the repair. This keeps the repair flat and not wavy. — Always use an X design to sand the repair. This keeps the repair flat and not wavy.

Here is the final repair in 80-grit. To finish the job, the filler needs to be sanded with 180-grit, primed, blocked with 300 grit, re-primed, blocked again, and then sealed and painted. — Hither is the final repair in 80-dust. To finish the job, the filler needs to exist sanded with 180-grit, primed, blocked with 300 grit, re-primed, blocked again, and then sealed and painted.

Bodywork is a dull, boring task that takes time to master, just is easy to learn. Don't exist afraid to utilise Bondo, as it is a good quality production that is a must-accept for any body repair project. And don't worry if y'all screw up, you lot can always sand it off and start over.

Cheque out all the paint & torso productsavailable on NAPA Online or trust i of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more than data on how to use plastic torso filler, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Jefferson Bryant View All

A life-long gearhead, Jefferson Bryant spends more time in the shop than anywhere else. His career began in the motorcar audio industry equally a shop director, eventually working his way into a position at Rockford Fosgate equally a product designer. In 2003, he began writing tech manufactures for magazines, and has been working as an automotive journalist ever since. His work has been featured in Car Craft, Hot Rod, Rod & Custom, Truckin', Mopar Muscle, and many more. Jefferson has also written 4 books and produced countless videos. Jefferson operates Red Dirt Rodz, his personal garage studio, where all of his mag articles and tech videos are produced.