When applying bondo and ect. is it best to use thin coats and build it up or use a thick coat or two ?
When is the thickness of a dime laid flat then its done with one coat, right? Its best with better metal work but if necessary filler in manageable layers. Just be sure to break the surface fully with sandpaper before adding the next layer. Try to keep each successive layer bigger than the last, meaning each batch is mixed bigger and covers more area. There's not much worse than finding a low spot in a panel that's been filled and blocked and then trying to fill that and block it down - it messes up the earlier work and you just about gotta start over with one more coat. The example on the right will make you work 5 times as hard, put more mud on the floor, more money out the window, for a result that makes you "one more coat" insane. If you have a panel that has 42 dents, fill 42 dips. Maybe you need to fill and DA them twice to get them up. THEN skim the whole panel. Don't skim the panel, block it all down and try to fill 33 of the 42 dips you find left in the blocked mud. Knowing when you're ready for the final skim coat means you only have to skim coat and block the whole panel once. It's the high spots in the metal that really ruin a days fun of body work. To get a car straight the entire surface of the panel needs to come up and meet that hight spot in a smooth transition. High spots go away with a hammer and dolly and or shrinking. Think of a polished granite counter top, now glue a Nickel in the middle of it, that's one high spot. How do you build up to that high spot? Cover the entire surface by the thickness of that one Nickel .
Doesn't make the slightest bit of difference. It does not dry from the outside like paint. It hardens chemically like cement. Put it on as thick as you like.
31Vicky and Rusty, Thank you for your answers, you have been a big help. I need to redo some work someone else done before I bought the car. Thanks, Ray.
The biggest problem I see with fillers is that the filler and the metal expand and contract at different rates. Around here, temperatures can go as low as -40 and as high as 100. The thicker the filler is, the more likely it is to crack or come loose from the metal. It looks good for a few years then cracks.
This is true to a point but there are a couple of issues that I see all the time when guys try to load it all on at once. They almost never get it pressed into the metal properly which can lead to adhesion problems. Your first swipe of filler should look almost like there is nothing but resin there you should be pushing mostly resin right down into the sanding scratches. When guys try to apply all of there filler in one pass they almost never do this because they don't have the work time to accomplish this. That leads to the second problem you see when guys try and do it all at once they under catalyse their filler so they have more work time. As I mentioned in a earlier post that can lead to a pile of other issues. Finally the top will actually cure faster than the inside if it is warm out or if the metal you are working on is cool as temperature does effect cure times with polyesters and this can trap air inside which can drastically increase the number of pinholes in your filler which will mean you will have to reapply anyway so you haven't really saved yourself any time and if you have taken the other short cuts mentioned above you will have other issues to deal with and some of them maybe down the road. As I mentioned in a previous post this happens due to improper use not the material itself. I live where we get the exact same type of temperature swings and deal with shops every day that use filler and in 11 plus years of doing this I have not seen a single example of filler cracking or falling off if properly applied unless the paint surface hasn't been compromised and water has gotten into the filler.
between coats of filler : In order to show,highlight the low spots between coats of primer it's suggested to shot a dark primer over the filler I,ve been doing this with a( Rustoleum) rattle can primer . Now I,m told this is not compatible with most other paints because it is a oil base ,not to use it for this purpose. True ?? Gene
They make a guide coat specially formulated for that, plus Almost any filler or primer has a quality of a guide coat built right in generally being darker where its not been sanded yet The guide coat product works better than almost anything else and won't make you ask questions.
My friend had a Lamborghini , we stripped it it and the whole car was skim coated from the factory.....blew my mind , couldn't believe it......
Thanks for the pic '31Vic. Great point about filling the individual lows first and then skimming the whole panel. I'll be paying more attention to that in the future. If I ever try plastic filler......
I'm guilty of some scuplting in my younger years. Pop rivet a patch, catalyzed resin in the seam, pound the seam in with a ball peen, fiberglass both sides of the seam, and lay on the bondo brand filler. The 2 cars I did this on would have gone to the scrap gods if I hadn't put them back on the road, 65 impala 4 door, 67 chevelle, both 6 cyl. Saw the impala 10 years later and all the repaired areas were holding, but it was rusting in other places, I couldn't believe it. Earl Scheib paint job still on it all chalked to hell, blue metallic looked like it was dipped in flour. So the guy that is now trying to restore them, is cursing me, but at the time, mid 90's, they were beat to shit rusty cars that no one wanted. I parted a lot of cars out and these were borderline parts cars, only reason I saved them is they fired up, trans shifted, and I needed a winter car each year. These 2 cars are why bondo gets a bad name, but it has also kept a lot of cars on the road to be restored later. I'm a reformed bondo abuser, skim coats of evercoat products is where I'm at now.
I was just talking to my buddy about this. If you got to a show and look down a car and it's straight. There is filler in it. Go to a car lot and look down a brand new ford. It would make you want to puke. I've worked at a high end rest shop working on fiberglass, steel and aluminum. In any case- these cars all got skim coated or ploy filled (spray able filler.) It's the only way to make the illusion that the car is straight. There are a lot of little things you can do to ensure that your filler doesn't move around onyou. Like not filling grinder marks-rather smooth them out with a finer grit (obviously not to smooth) so then your filler expands and contracts from temp changes. Otherwise you may end up seeing those grinder market in the finish of you paint eventually or as soon as you buff it. That is an extreme condition tho. It all comes down to abuse of filler, it's happens in every industry. There's always someone that thinks they know the better or faster way.
Yeahhhh, the only way to get them Q-ball smooth and lazer straight is by a skim coat on the entire panel and blocking it down with a longboard. Some guys really want to be able to say that there is "no mud" in their arrow straight car, see if they will tell you how many gallons of filler primer or spray Poly are on it?
I bet it's not show quality straight. I work at a dealership and I'll be the first to tell you they get worse every year.
1980 my birthday and my buddies and i got to drinkin and decided to fix a 50 olds fastback that was in backyard for a show the next weekind. was pretty eatup, we stuffed newspapers and anything else we could find in it then gallons of bondo, torched the coilsprings to lower, replaced the rusted off exh. w/homade lakespipes, black primer, flame job, striping by my friend. motor ran good, we drove it 200 miles to show,gas tank fell out on way home. with all that bondo the car was in newspapers, magizines, a band used it on the cover of their album. had alot of goodtimes in that car and the bondo never fell out.
My 57 was punched in the side, they replaced it with a 4 door quarter and the welds were off(over an inch) so they just mudded the piss out of the car until it was level. I knew it was bad when we got the car, but it was rust free and only that dent in the whole car. Took a lot of grinding to get deep enough to cut it all out. That repair was over 20 years old. Currently stripping my unibody and fixing it. almost 2 inch deep mud between the door and rear wheel well. knew it was bad as well but not THAT bad. They never put a hammer to the truck, just a wheelbarrow full of bondo. It sure sticks well. Going back together its getting SOME filler on it again. and maybe thicker than a dime. but for sure not 2 inches deep!
Did you know lightweight body filler was created by the fuel crisis, not by big heavy chunks falling off? It's true, it's true! This and more fun facts here: http://bondo.com/about-us
When you layer your filler it cures at different hardness and makes it hard to block slick that why it better to put a glaze coat on top to really get it slick. But you must do your metal work to the point where it only takes a dime thickness to fill. I worked in a shop for years where you had to buy your own materials because there were two many cave&pave body techs. I always worked my metal longer and spent less time filling it and always ran more hours than the pavers.
Nobody has mentioned cheese grading.. I used to put the filler on [early 80's White Lightening] and once set up some I would cheese grade close, let set up totally and block sand..Still on the car 35 years later, no issues..Never seen Bondo Boyd do it...
Anyone that is still cheese grading filler needs to get caught up with new filler technology and/or application techniques. There is absolutely no need for these types of techniques with today's fillers. If you are needing anything coarser than 80 grit you are either applying way too much filler or using crap products.
Chill...Didn't say I'm doing it now...I said I did it in the early 80's and no one has mentioned it..
I never said you did hence the "anyone". I was just replying to your question about no one mentioning it and I can tell you it does still happens way more than it should.
Old habits die hard I wanted to say that old habits and bad attitudes die hard but I figured I'd better not because someone might think I might be refering to them
Wait, I'm still doing it that way, and I have a tall expensive stack of 36 grit long board paper! I'm still working with the same gallon of filler I've had for years. What does the new stuff do, self leveling?
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