Best kind of BONDO?

Canada_Dry

Hello,

I need some bondo, or some sort of body filler/putty to fill in and smooth out my old school case. I will be adding a custom look to the sides and definatley the front of the case (plastic) and need to know what the best kind of bondo/putty is for this.

I need to build off of the case as it is, and add alot of bondo to make it look entirely different, so it has to be strong, not strong as in hit it w/ hammer and not break strong....but if i bump into it i don't want it to break off all brittle.

thx

Forlorn

Theres car bondo. Check a craft store, they may have a bunch of different kinds of hard drying putty.

Canada_Dry

i know there is fiberglass bondo, and automotive bondo, w hich works best on plastic?

deadly-app

just rough up the plastic. I have used automotive...works alright, but it does chip off and such fairly easily if it comes far up off the surface.

Canada_Dry

i have the plastic all sanded and scuffed...anyone use any putty? seems bondo isn't going to work so well :(

Uncle Dirt

I never really used it, but you could call an Auto Body shop and ask someone who knows all about polymers and puttys. They could give you more details than we could. You could also use a good friend of mine called Google. Google is my best friend on the internet and helps me with almost everything I could ever want to know in life.

TimberWolf

In general, if you're just filling small flaws or "blending in" a small and low feature - a raised panel, for example - you can use glazing putty (also referred to as "spot putty"). Glazing putty is generally laquer solvent-based, so it tends to bond with the polystyrene plastics commonly used for case bezels, and will also bond to primed metal.

If you're trying to blend in a larger feature that projects above a panel surface, you need to first ensure that "the feature" is securely mounted to minimize panel flexing or feature movement, which can cause cracking along joint seams. Molding in features like this, or creating effects to simulate a "carved" appearance should be accomplished with Bondo - but "the fill" needs to be built up in layers of approximately 1/4" to allow for proper curing, and to minimize the effects of shrinkage. If you're simply creating raised areas for that "carved effect", you can build up the work area with strips of plastic first to minimize the amount of filler required. The strips can be secured with glue or sheetmetal screws - but the point to keep in mind is that you want to use only as much filler as is needed for the task . . .

Use regular Bondo on areas and features that are well-supported; use the figerglas reinforced stuff to provide additional strength where needed - but the 'glas filler will take more effort to sand into it's finished form. Mix the catalyst (hardener) as per the directions, and strictly avoid the n00b tendancy to use too much hardener: It will drastically shorten the time you can work with the mix before it "kicks" (starts to cure), it can generate enough heat to melt certain plastics; and it will cause the cured filler material to become harder to sand, excessively brittle, and prone to cracking.

There are various types of "Sur-form" tools - they're sold as blades and handles, and they look a bit like cheese-graters - that can be used to roughly shape Bondo as it starts to cure. You don't need to buy the handles, as the blades alone will be fine for "hobbyist" projects. You use them to knock off excess material so you don't spend as much time on sanding; and they're handy, but not absolutely required. If you are using one, you wait until the filler is just hard enough that you can leave a scratch in it with your fingernail, and then perform any rough shaping. They're relatively useless if the filler is fully hardened, so at that point just use 60 or 120 grit sandpaper for your shaping work.

Once the filler is sanded to it's final shape, you may notice small voids and / or pinholes - this is normal, and they should be primed and filled with glazing putty as needed.