The Stovebolt Site Forums The Shop Area Paint and Body Shop Types of Bondo?

I am curious what is the difference in bondo colors. Is obvious that the previous owner of my 55 used a white filler. Is it a better type. I have only found grey with red hardner when I have bought some.
Please educate me on bondo...............

Thanks,

Roger

Oh, boy, where to start..... There are several different types of fillers, each with it's own purpose. I'm no using the term "bondo" as it is a brand name. The gray/red is the common stuff that is used as a base filler. It cad be primed and painted over, but it is somewhat porus. There are also what they call "spot/glazing" putty. That is most likely the white stuff that you are seeing. It usually somes in a squeeze tube, and is either white or orange/red. There are also blue and green varieties as well, depending on maker. There are also finishing/glazing putties that requir a hardener like traditional filler, they are susually yellow/gold or white in color, depending on the hardner color.
Generally, you will use the regular filler to do the bulk part of your repair, then the glazing putty to get the smooth finish and to seal the base filler. The stuff in the tube is best left for small repairs, they dry like paint (evaporation of solvent) and have to be left to dry for several houres before sanding. The other types can usually be sanded in 15 minuits or so.
You'll want to get quality fillers, go to the flaps or auto paint store to get the best fillers. Personally, I prefer Dynatron's professional products, Dyna-Lite for base work and Putty-Cote for finishing. Auto-Zone carries them. Bondo brand is also good, they are a division of Dynatron. Evercoat has quality products as well, I personally have not used them though. You'll want to get some rattle can sandable auto primer to spray a guide coat to help find high and low spots when you sand. I prefer the dark gray myself as it's easier to see.

"Bondo" is a trade name for putty resin. I don't have any experience with these filler putties, but I've been working in the composites field for darn near forever...at least it feels like it sometimes. There are basically three different components that make up the compound: resin, catalyst, and filler. From the performance perspective, epoxy resins are better than polyesters. ("Bondo", as I recall, is polyester.) Polyester is also the base resin in what is generically called "fiberglass", like the old Corvette bodies.

You add a resin-specific catalyst to get it to change from a liquid to a solid. Different resins require different catalysts. Some catalysts are "hotter" than others. Think of Devcon epoxy that you buy in the hardware store. You can buy 1 minute, 3 minute, and 15 minute epoxies, but this is really just a tweak to the catalyst. Not enough catalyst and your resin will take forever to cure. Too much can make it unworkable. More isn't better.

Filler is the stuff that makes it great for body filling. It is usually pulverized on a microscopic scale- the finer it is, the smoother it can sand out. Too much filler will reduce the amount of resin, sorta like aggregate, sand, and portland in concrete. You want the right ratios.

Like Bill said, you want to make sure you get the right one for the job. Don't think they are all the same because (I believe) each one is formulated for a specific application. You don't want to do the work twice, so I would recommend buying on the expensive side "just in case."

Bill

Thanks fellas! That was the info I was lookign for.

Thanks fellas! That was the info I was lookign for.

One last thing that I forgot to mention: those resins are generally clear to amber in color. Fillers can be gray to white, depending on the material. Catalysts tend to be fairly clear. The manufacturers usually add a pigment to the catalyst. This is to help the user know that the catalyst is evenly mixed throughout the putty. If you have streaks, keep stirring! The pigment has no effect on the performance. One manufacturer's "red" filler can't be compared one-for-one with another manufacturer's because it is nothing more than their choice of pigments. I'm not aware of any industry standardization of color/application.

Bill