Sanding body filler. Newbie question.

Thats what I do. I went to HS VoTec in '79~'81,,and learned that way. While that seems like alot,, it shows when you're done. I've won local car shows and received business just by the cars appearance there. We have some real HotShots here on the Hamb and I'm sure they do even more than those steps.As a Great Hamber once said :
It's body work not body fun.

 

Thanks for the advise guys, this has really helped.

 

Clearly, there are many ways to do this. The point is, you want to sand the Bondo smooth enough so sanding marks don't show through the paint later on. If you are using filler primer, you might not have to sand the Bondo quite as smooth as otherwise. If you can see the marks through the primer, you will see them throught the paint, too. Good luck.

 

sure, there is many ways to skin a cat , and they all will work.

the question here was whether you CAN prime over 80, not whether you should or shouldnt. i would agree that the finer the better, but some situations will require that to keep a panel flat you may have to finish with 80. i just wouldnt want a new guy to body work not knowing all the options , and the fastest way to straight panels



skull

 

If you have nothing better to do for three or four years I'd suggest you final sand the filler with 400 grit.

 

180 before first coat of primer, 360 after..........

 

wheres the popcorn icon?....

 

There's a great NING sight for questions like this. I know the HAMB is just the best all around site, but try www.autobodystore.com if you want professional help with paint and body questions.

 

I guess there are no rules, whatever works but........the coarser the paper when sanding filler the smoother it will come out. I do a final block on filler with 80, then load it up with a good CATALIZED primer then final block with 400 or 600 depending on the color your going with. Do not wet sand any kind of filler it will absorb the water and cause problems down the road. You can also use a softer filler,I use Evercaot, over the final shaped bondo to fill scratched and pinholes before the primer. Its worked for me for years

 

Just for a little of the body world by Palos. I like others have been at it for longer than I care to remember and have seen and expierienced the evolution of automotive paints & materials.

As far as finishing bondo in 80 grit question goes . This was common practice for years in the shop in the days of lacquer finishes. This practice was part of the reason for some of the earlier comments of having your paint job look like hell and not to do it. Finishing the plastic 80 was not the reason for the problems , using a low quality fast evaporating lacquer thinner in the primer was the cause of many issues. What would happen is the fast thinner would allow the primer to bridge the sand scratch of the 80 grit paper . Once the panel was primed , prepped and ready for color, things would sometimes be ok and other times all hell would break loose. The choice of the color thinner , temp and humidity conditions, as well as how wet the lacquer was applied was instrumental as to what result you got. If you used a hot thinner or added retarder to the color and applied it over a primer that was thinned with a cheap/fast thinner, the hot solvents in the color would reflow the primer , causing the primer to sink into the bridged sandscratch . These aggressive solvents could also cause a host of other paint problems. The best cure for these resulting issues was to always use a quality mid to hi temp thinner in your primer. Most production shops at the time did not like to do this since it slowed down production and cost more for the good solvents.
Todays materials have been reengineered to overcome these past problems. Most of todays materials cure by cross linking and not by solvent evaporation. There is no difference in finishing in 80 and applying several coats of an epoxy primer and blocking to finish or applying a coat of polyesther putty to plastic finished in 80 and then blocking it in 180 to finish your panel. It is sometimes just easier to evenly apply a couple coats of primer than apply polyesther putty with a spreader.


If you dont have any formal training in the products and their application , please be careful about the info you provide and use. Yes it may have worked for you in one or two situations even though you misapplied the product or used the wrong one for the situation. Always refer to the manufacturors tech sheets and MSDS before using and applying materials . You would be amazed at the amount of important information contained in the papers , as well as how much easier it makes things when you use the product for what it is designed for. These instructions are from the people that designed, tested and manufactured the product. Working in a shop or garage for a short time without proper training does not make one an expert on these materials.

I dont mean any ill by my statement but my point is this.

I have met many skilled techs in may time and I have also come across many that think they are skilled techs . The difference is in who, what and how they were trained. Yes there are aspects of the trade that some are naturals at but even the greats in sports needed the right coach.

 

With the modern Waterborne paints, a lot of manufacturers are starting to see bleeding as a problem again even with the blue green hardener.

I am not saying not to prime over 80 grit scratches, I am saying to follow your manufacturers reccomendations to a tee.

There are a lot of top restoration shops out there that do finish there cold filler in 80, the only difference is that they generally coat that with sprayable body filler and then let that sit for a couple of days. At that point, they will block their work into 180 and then use a conventional primer/primer surfacer or an epoxy.

 

Amen

 

If you DA with a 180 the finish will be same as hand rubbing with 360.

 

catylized sealers and primers should help avoid bleed.

in the 2 years we have had water here, we havent expeirienced any bleed as yet, who knows down the road.
we are using ppg wich is the only true all water, and seems to be less violent than some of the others that are actually a water soulable solvent system.
on expensive custom jobs, i still sneak in solvent base and use the methods i know will hold out in the long run. the water does seem pretty good so far though

 

im sorry if you prime over 80 but dude i have never seen that done ...i have been around old skool motor heads and body men my whole life my god damn grandfather was a body man for christ sake and so on and so fourth ...and been in many custom shops .. worked in custom shops and never ever saw anyone do as you described .but your proboblyright it might work for you and also ..just because i dont have blah blah blah body shop under my name that certinly does not mean i am wrong and dont know what the f^ck am talking about .. i do $hit the way it was taught to me by very exceptional body men . dudes that sell there cars for over 100k sodont go telling me i dont know what i am talking about

there are alot of ways to do body work .. if you dont agree with me fine but dont tell me im wrong becasue you do it differently ...im not a expert but i know how i was taught and i know how it should be done in my opinion..

maybe i was wrong for telling the dude not so prime over 80 grit ...i guess it can be done i just have never seen it done ever

 

Decontrol is absolutly correct with his info. If anyone reading this thread is doing so just to confirm what they are doing is right, and not listening to the proper way, than we will continue to see paint failures at 3 months to 5 years. If you take a PROFFESIONAL auto body course and not some course offered by someone who has "done" bodywork for 30 years but still mixes his filler on cardboard then you will be okay.

I have seen people throw sunshine up their own a$$ about their paintjob where a blindman on horseback could have done a better job with a roller.

If you are proud of your accomplishment then that is great. But, if you are teaching someone (even on this thread), then you better have more to back it up than "I have done it this way for years".

 

I have never seen the "don't mix bondo on cardboard" argument proven one way or the other. I heard about it in '96 but the guy didn't stay long as Foreman of the shop..

 

The styrene liquid in the bod filler absorbs into the cardboard.

 

OK,,I'm saying I haven't seen a single failure since '78 due to mixing Bondo on cardboard,,however I'm open to learning something new.

 

I dont see the prob with shootin primer over a rough surface???????? I've primered over 36 for a temperary seal, I wouldnt primer over 80 then paint if that what you guys are trippin on

 

It is not that you WILL have a problem, its that you COULD have one. Styrene liquid is the solvent within our body filler. If you were to paint a car without a thinner or reducer, could you make it work? yes. Would it work better with the recommended amount of thinner? Yes.

My point is, people that teach any topic should know how to do things properly. I go to many training seminars all around north america every year to learn about new and changing technology with regards to auto body. What was considered industry standard just a few years ago now seems archaic.

I know of several body men that got their body ticket 30-40 or even 50 years ago and have never gone for update courses. They will be the first to admit that they have fallen behined. There are also many who keep on top of changes and strive to out do their own work every day. Those are the people that I have always looked up to

 

Your not supposed to mix bondo on cardboard?????? Man i've got alot to learn

 

I'm one of the old guys that has always finished my plastic in 80g; prime and guide coat, block with either 180g or 220g, maybe reprime or another guide coat and finish with either 280g or 320g. The 280g would be good enough for the acrylic enamels and I've use the 320g for BC/CC.

I almost never use a cheese grater, just a grinder; flat like a file. I usually put my plastic on and let it sit for about an hour and grind, then another coat of plastic if needed. I always felt the cheese grater pulled the plastic away from the metal.

 

Make sure you use a sanding block. That will defenately help...

 

you should prep(sanddown or sand blast w.e./ base coats of primer)
sand with 180-220
skim whole car
sand with 80 grit( i know, very controversial but its true) real quick to knock down the poorly spread filler(no offence)
once knocked down proceed from 80 to-180-220-400
filler primer
sand with 220 and 400
Surface primer sand with 400 and 600 and wetsand as much as youd like (theoretically)

longer the block you use, better the finish( on wide open areas like a quarter panel or door etc

i have NOT been doing this for YEARS seeing how im still in college however, i apprenticed the guy who painted these cars and also work at an industrial finishing place where i do prep work, paint and powdercoat and its what I have picked up thus far.

doesnt mean im right^ but it also means even though theres somewhat of an art to body work, it also means there are SEVERAL other ways of approaching it.

dont forget to criss cross pattern, and the more times you repeat the steps the smoother it'll lay out

 

NO!! Not only can the cardboard absorb the resins and catalyst which will change the fillers proporties but you can also get tiny particles of the cardboard in the filler that can trap unwanted solvents, excess amonuts of catalyst /resin etc that can all casue problems later on.

 

Every thing i know about body and paint i learned from my daddy, then i took classes and learned the right way to do things! I now just do it as a hobby for myself and friends, so if something fucks up? Oh well! The kid that started this thread is doing it for himself i'm sure his first job wont be a 100 point job. So all this technical bicering is just plain silly!
Boulderdash, get yourself a gallon of bondo, a quart of evercoat, a long block, some 36,80,and 150 dry, a gallon of catalized primer (its not legal in some areas but who cares) and then some 220,320 and 400 wet and have fun. If you fail the first time grind it down and try again, it aint brain surgery and it dont have to fly so we're good

 

It is not technical bickering there is a right way and a wrong way to do things so why let someone teach someone new the wrong way. Just like paint there is a standard process that filler manufactures recommend for using their products. They do this because they test these products endlessly and know what works best. You are right his first attempt will probably not be 100% but why make it harder and less enjoyable or reduce the chances of him succeeding by saying just do it anyway you want or do it in a way that is not recommended because it happened to work for me in the past?

 

so , you and decontrol dont think you should prime over 80 on filler. decontrol even states he has never seen it done before.......reasonable statement, but dont mean that its wrong to do it that way.

the professional courses you speak of , generally are for production work on newer cars. they are in a different world than a guy doing a 15,000 paint job on a custom. sure, if i was fixing a small dent on the hood of a honda, i would go much finer than 80, as they teach ya in ppg school(yes, i had to attend all those clasess, last april most recent)

but for a guy who just chopped his top, or is doing a qtr on a merc, or cad, 80 and reprime is gonna be neccesary. these body schools dont teach how to do those kind of jobs, you gotta learn on your own, or from guys who have been doing it. i would take the advice any day from people who do the work , than from some one who just reads the msds papers. sure , they are important, and should be read, but expeirience is the best teacher.

after a few years you get a feel for what works , and what dont. not only do i prime over 80 on filler, but also re-prime over prime tht has been 80'd
msds sheets and overhaulin aint gonna teach ya how to paint.

but to say something is "ludicris" because you havent tried it, is equally missleading to the new guys trying to learn.



skull

 

SKULLHAT, good point when blocking a car, 80 prime, block w/80 prime, block again w/80 prime again, done it a hundred times. I dont think you could do a very good job blocking a car w 600?????