whats the best auto body filler to use
There is non a more maligned automotive product than "bondo". Plastic body filler is most often referred to past the make name "Bondo" (made past 3M), and its bad reputation comes from decades of poor application and misuse. Virtually every loftier-cease custom car or restoration has some amount body filler on it. Using it on your daily driver or project is not a bad thing, every bit long as you utilise it the right style. Learning how to utilize Bondo the right way isn't every bit difficult as you call up.
History of Bondo
Similar almost plastic body fillers, Bondo is a lightweight polyester-based plastic body filler that was originally developed as an alternative to lead body solder. Old school torso shop techs used to cook strips of lead with a torch to fill body imperfections and joints. The Bondo brand name was created in 1955 by Robert M. Spink, just a few years after the use of lead trunk solder began to be prohibited. Many bodyshop men of that age were non sold on the thought of using plastic body fillers, but over time, information technology became apparent that the lightweight, easy to utilise nature of torso filler was a do good over lead. Not to mention that lead body solder is very unsafe to work with given the need for a torch to heat it, pb fumes, and even lead dust 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 awarding. We've probably all seen a motorcar 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 make full large dents, rust, or other major trunk damage. Information technology does non move or or behave like a metal body panel. Why would you waste material fourth dimension laying downwards a gorgeous paint task if you know the gigantic hulk of plastic body filler behind information technology could really pop off in the hereafter?
You tin can actually bank check whether a auto has too much body filler by using a refrigerator magnet. Put a slice of paper between the steel body panel and the magnet (to protect the paint), then meet if the magnet sticks to the car. If a magnet won't stick to a steel trunk console, information technology may be loaded with plastic torso filler.
Working With Bondo The Correct Way
Now that you know a little more than about plastic body filler, yous can start working with information technology the correct way. Just at that place are a few key points that you should know before working with body filler:
Thickness Matters
There is no minimum thickness for Bondo, but there is absolutely a maximum. You do not want to utilise torso filler to anything that is thicker than about a 1/iv". That does non mean information technology tin can't exist done, but the repair will not last as long. Eventually the filler volition compress and possibly crack, or even pop off! The full general dominion of thumb is that if the dent it deeper than 1/viii" you demand to do metal work first. Recall, your overnice paint job depends on a solid foundation. Simply troweling on the filler may look like the easy push, but that slab of filler may decide to fall off some day (we've seen it happen).
Set up The Foundation
What yous are working with needs to be properly prepped BEFORE y'all employ any trunk filler. Exercise not slap Bondo onto a smooth painted surface, it is not going to stick very well. The pigment should be sanded off, to the blank metal, and and so use the filler. A 36-grit to 180-dust surface is ideal for body filler application so that the filler has a good rough surface to grip.
Not For Every Location
Don't use torso filler on full gas tanks, or anywhere that gets hot. Bondo is resistant to fuel, but simply after it is cured. If you lot are smoothing out a gas tank, that is swell, it yous are trying to ready a rusted out gas tank, this is not going to do a good job. Don't confuse Bondo with JB Weld, the two are non the aforementioned.
It Won't Magically Fix Rust
Torso filler is non expert for rust repairs. You cannot slather some Bondo over rust and expect information technology to end the rust or stick to it for that matter. For rust repairs, you must first remove any rust scale from the metal. If in that location are holes in the metal, y'all are much better off cut it all out, patching it with new metal, and then working the body filler from there. Any rust left under the filler will continue to grow, and so don't be surprised if a pocket-sized repair turns into a bigger problem down the road. If you absolutely must use body filler to make the repair, then you should remove all the rust scale, add a backup screen to cover the holes from the back side, then utilise Bondo Bondo-Drinking glass over the rusted area, sand and terminate out with regular Bondo body filler for a stronger repair.
Pay Attention To The Mixing Ratio
The mix is crucial. Nigh of this comes from experience, simply yous can get close to the optimum mix with this tip- use ane:1 ratio of inch diameter of filler to inch-length of hardener. A 4-inch diameter of raw filler needs a 4-inch ribbon of hardener at room temperature. If it is hotter (above 85 degrees), utilise slightly less, if is colder (below 65 degrees), employ slightly more. If your filler hardens too fast, y'all used too much, if it takes too long, y'all didn't use enough. You only want to mix what you tin can use in most 10 minutes. Properly mixed, torso filler will begin to thicken in 10-15 minutes, and be fully cured in thirty. Until you get the hang of mixing it is wise to buy a bit more than plastic body filler than your project needs so you have room to endeavour once more without running back to the shop.
Practise not whip the body filler while mixing it. This will incorporate a lot of bubbles in the filler, which means more than pinholes to fix subsequently. Use a ho-hum and deliberate figure-10 pattern, wiping the filler across itself.
Awarding Technique Is Key
You can use plastic or metal spreaders, choice is upward to your personal preference. Metal spreaders last longer and provide a more defined border, only plastic spreaders are cheap and can be custom cut to match shapes. Use the filler to the panel, pushing the filler into any crevices. Wipe the filler as polish and level as possible, simply leave plenty of extra filler to a higher place the surface level to sand the repair smooth. Better to accept a picayune too much filler and sand it off, than accept to mix up some other batch of filler for a depression spot.
Get Fix To Sand…A Lot
In that location are two schools of idea on when to sand filler. If yous are doing general bodywork, leveling wavy panels, fixing small dings, etc, and then wait until the filler is fully cured, almost xx-30 minutes. If you are using a lot of filler or doing some shaping with the filler, you can apply 36-grit sandpaper when the filler is in the "greenish" stage, this is solid, slightly rubbery, just not fully hardened. Using low-cal force per unit area, you tin knock off large amounts of filler to rough-in the shape needed before the filler hardens, making sanding more than labor-intensive. And don't forget the respirator and prophylactic glasses, fine filler dust tend to go 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. You should non be able to feel where the metal stops and the filler begins. Any defect yous see or feel in the filler will be amplified when the pigment is on the trunk, so check the panel repeatedly. Large repairs require extra effort, as yous can easily get waves and ripples in the bodywork when working a large area. Never sand in straight lines, instead use a criss-cantankerous pattern, up and downward, side to side. This eliminates waves and results in a much better repair.
Bodywork is a slow, dull task that takes time to master, simply is like shooting fish in a barrel to learn. Don't be afraid to use Bondo, every bit it is a good quality production that is a must-take for whatsoever body repair project. And don't worry if you screw up, you can always sand it off and start over.
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Jefferson Bryant View All
A life-long gearhead, Jefferson Bryant spends more than fourth dimension in the shop than anywhere else. His career began in the car audio manufacture as a shop director, eventually working his way into a position at Rockford Fosgate as a product designer. In 2003, he began writing tech articles for magazines, and has been working equally an automotive journalist ever since. His work has been featured in Machine Craft, Hot Rod, Rod & Custom, Truckin', Mopar Muscle, and many more. Jefferson has also written iv books and produced endless videos. Jefferson operates Cerise Dirt Rodz, his personal garage studio, where all of his magazine articles and tech videos are produced.
Source: https://knowhow.napaonline.com/bondo-101-basic-for-working-with-plastic-body-filler/
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