help with bondo and fiinishing

i have asked this awhile back but am back again. i built a helmet and asked what type of bondo i should use before sanding. i was given some suggestions and got some from my uncle but when i put it on and let it dry i would not sand at all... so if anyone has any links to the good bondo that everyone uses that would help alot.

I use the automotive bondo you can pick up at Walmart, Autozone, or Advanced Auto. Make sure you read the side of the can to find the mix ratio, as too much or too little hardener could cause issues. When you start sanding you'll want to use a "higher" grit sand paper. Start with an 80-120 grit and work up from there. The lower the number, the rougher the sand paper.

Hi. I'm surprised that the bondo you used couldn't be sanded. If you're not familiar with working with the material you may need to apply more pressure with a rougher (low) grit sand paper around a sanding block to more effectively sand down the hardened bondo.

I say I'm surprised because bondo, which really is a brand name of an auto body finish, is made to be sanded. Anything with the bondo brand should work for your purposes. Below is a link to Home Depot for typical bondo (a gallon of this runs around $20, the least expensive that I've found is at Walmart). If you can find a gold or professional grade bondo I find that this is easier to sand. Below is a link the bondo product found at AutoZone. I couldn't find it on Autozone's website but you can find an off-brand gold filler there for around $32 a gallon which works great.

http://www.homedepot.com/p/3M-1-gal-Lightweight-Body-Filler-PN0265/202077783
http://www.autozone.com/paint-and-body/body-filler/bondo-professional-gold-filler/392484_0_0/

You can find various selections at auto stores, hardware stores (usually somewhere near the paints section), or places like Walmart (in the automotive section). Take a look around to find where stuff is cheapest. In addition to straight up bondo or other body fillers you may find products that combine filler with fiberglass threads. I'd suggest avoiding this material for your purposes as it's intending for greater strength applications and would cause you extra difficulty in sanding as well as a rougher surface to start with (since threads would be present in the mix).

Hope this helps. Again, you may want to see if some more elbow grease will allow you to sand what you've already got but if it doesn't then it's always good to try out new things. Good luck with your project.

Edit: I didn't see the shiznite88's response while I was typing but I agree 100%.

thank you both for the Info, the bondo i used seemed kind of to thick and hard, it might have been old. and it some what would sand but i live in oklahoma so the weather is weird, so when ever it came close to drying in warm weather it would get super cold out and the bondo would remain gunky. but i will get the bondo and sand paper like you guys said and try from there.\

I wrote a big step-by-step guide on using Bondo for this very occasion: http://robtaylorcase.com/blog/?p=399

That should cover any questions, I think. Don't bother wasting money on "Bondo Gold," it's not significantly better than regular Bondo. If you later feel the need to upgrade to high-grade filler, look into Evercoat Rage Gold. I haven't looked at pricing on that yet, but I'm sure it's expensive. Regular 3M Bondo is about $20 a gallon at Home Depot in the paint department.

If you're not US-based, you'll have to clarify. There are definite regional variations.