BODY, TECH Bondo 101 (Magic dent erasing compound)

[overspray]

OK--Here's the gospel on body filler/bondo over primer. I used to work as a technical/sales rep for the company that makes rage filler. I know the guys (chemists) that developed the resin for rage filler. I've been a bodyman/painter,sales rep and technical rep for 30 years. The resin in rage and other body fillers is fiberglass (polyester) resin. Today's resin technology makes the adhesion of these new resins as good or better than most epoxy adhesives (glue). They are designed to really stick! Also they are somewhat flexible when used properly. Most or probably all filler manufacturers design and reccommend them to be used over clean and prepped (grinding with course-36 grit) and rust free (sandblasted)and dry (free from moisture) BARE metal. They will stick to epoxy primers with mechanical adhesion-they DO NOT chemically bond with epoxies. If you put filler over epoxy primer it has to be fully cured with no solvents (thinner-reducer) left in the primer and still should be sanded with a course grit and cleaned. In other words- It's a wasted step that may or may not cause adhesion problems later on. Most critical is to be clean and moisture free. Body filler resin is a thermal set plastic-it cures with heat. The hardner-MEK peroxide is a catalyst that produces heat in the resin. It needs to be at 64 degrees F minimum to cure-best is 72-80 degreesF. (If you live in a warm climate still read on but it may not apply to you.) If the metal is cold the filler will cure from the outside in and could trap some moisture and solvent from the resin underneath-causing adhesion or bubbling problems later. (Styrene is the solvent in resin and produces the smell/odor we associate with bondo and fillers). Also moisture (humidity in the air) will condense on the surface of the cold metal. This is the same effect you get when the mirror in the bathroom fogs up when you shower. (I hope you all shower). The mirror and the metal of the car are about 10-15 degrees cooler than the air temperature and the humidity condenses on them. If you warm the mirror or the car metal to about the air temperature, the moisture won't condense on the surface. Using a heat source to warm (NOT HOT) the panel will eliminate the moisture being trapped under the filler (which can show up as rust under the filler) and help keep the cure temperature even through the filler. This is the way the chemists designed the product to work. You can use extra catalyst to speed the cure, but too much will cause too much heat in the reaction and crystalize the resin which causes it to be brittle and break down (yup-more problems later). If you head to the autobody supply store for more hardner you may be using too much and looking at problems down the road. PreWARMING the metal and keepin the shop warm will let it cure more evenly with the correct amount of hardner. Heat lamps or lights should be far enough away so the panel feels warm when you put your bare hand on it (NOT HOT). The correct amount of hardner is 1 1/2 to 3%. Here's an easy way to figure it. On the pallet or board you mix your bondo or filler on put the amount you are going to mix up in the form of a circle. With your spreader or mixer divide the circle in half-50%. Divide the half in half-25%-half again-12.5%-half again-6.25% half again-3.125% (this is the maximum) half again-1.5% (this is the minimum). If you have a COLD shop put a small batch on a WARMED test panel to check the cure time-spread to about 1/4 inch thick. It should be fully cured in about 30 minutes to 1 hour depending on the temperature and hardner amount. (Yup, I know you can add a pile of hardner and get it to "kick" in a few minutes). A good cure time lets the gasses come out and gives ample time to work out the air pockets with the spreader. (eliminate "pinholes") After a few times you'll be able to gauge the amount of hardner for the size of the filler batch you are mixing. There is some room here for a little extra-but not a lot of extra hardner. REMEMBER, this needs to work with the temperature of the air and metal. Filler also contains talc (the mineral in talcum powder) which will absorb moisture. If you try to fill holes in a body panel, moisture can be absorbed from the back side and cause the area to swell and bubble. Also bare filler left in the weather (rain) for any length of time can absorb moisture and cause problems later. It will cost a lot less to follow these steps of correctly preparing the metal and working with the correct temperature range and hardner amounts than to even bother with epoxy primer as an underlayer. Between coats of filler DO NOT wipe with solvent (thinner).(Solvent will absorb into the filler). Rough up the areas not sanded and blow the dust off real good then apply a new layer. Thickness of the layers should not be more than 1/4-3/8 inch. If you put filler on too thick the heat in the reaction will be concentrated and higher in the thick area and could lead to crystalizing the resin in that spot making it brittle and subject to cracking later. Also too thick can mean you won't be able to get all the air pockets smoothed out. Use a primer surfacer system that is reccommended for the paint you will use. Self etching primers usually contain an acid and should not be used under filler ( the acid will slow down the cure of the filler resin). I like these primers for bare metal on my projects. I use them but grind them off where I do filler work. Also the acid in the self etching primer activator will affect the epoxy resin hardners in epoxy primers where they may not cure chemically but will still air dry. It is possible to put epoxy primer over self etching primer BUT ONLY if the acid is gone and the etch primer is fully cured. (probably a wasted step anyway). My preference is etch primer on bare sandblasted metal (I'm talking old cars here) bondo or filler on bare metal, a catalized spot or glazing putty (bondo skim coat), a good 2 part urethane primer filler and a good topcoat finish. Yup, I know how to make paint look like primer (suede). Now one more thing to screw up your minds-- today's bondo/body filler technology will adhere to properly cured paint and primers if they are absolutely clean and dry. They stick by mechanical adhesion- they grip to scratches-the rougher the surface the better the grip. Solvents (thinners and reducers) in paints and primers can work under the edges of the bondo/body filler area-and it's easier for this to happen if you have paint or primer under the bondo/body filler. Even when priming over filler on bare metal don't put so much on that you have the solvent affect or "lift " the edge of the filler. Use nice even coats and let the solvents "flash" (evaporate) between coats of primer. overspray

[Petejoe]

Overspray, Thanks for the post ! Great information.
I felt like I was read the Good Book with no indents or itemized portions. http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif I plan to copy this for future use. thanks !

[Deyomatic]

YOU READ MY FUCKING MIND. I honestly JUST looked through Tech-O-Matic to see if there was a Bondo thread already. I'm in the process of TRYING to make the spots I just filled look like they were never there and I'm failing miserably.
Thanks.

[overspray]

If you are beginning-do some test batches first. If what you put on the car doesn't look like it's "right"-grind it off and start over. Bondo is the least expensive part of body work. It doesn't work to keep going over a bad mix. It all takes time to learn technique. I've worked with guys that made Michaelangelo look like a "rookie" when it comes to sculpting. It usually takes me longer to get the shaping the way I want it- but I do okay. I'm glad I helped. overspray

[Nads]

Great tips, but man was it hard to read.
Anyways, what about catalyzed glazing putty?
Can it be put over a surface sanded to 320 grit without problems or not?
Is that too smooth a surface?

[overspray]

CATALIZED GLAZING PUTTY-- is basically a finer textured bondo. It has less pourous filler material added to the mix so it doesn't absorb solvents AS MUCH. A rougher scratch than 320 grit would be better, but that will work. The key to using this stuff or any catalized primer filler or spot putty with a hardner is to remember if you put it over a finish (paint or primer) that does not have a hardner, solvent or thinner will soak into the UN-CATALIZED product and not the CATALIZED product. The UN-CATALIZED product will swell a little from the solvent it absorbed and later (usually after you have painted the car) it will evaporate and shrink back down leaving sand scratches or a ring around the area. It's best to use a system with products that are 2-part (catalized) with hardner from the metal work to the finish. There so many good fillers, primers, glazes, and paints that are 2-part systems today. Back in the day of lacquer paint finishes on customs, painters would color sand the paint after it dried and repaint to get all the sand scratch shrinkage out. This process was repeated until the paint didn't show the sanding marks. They used to say- "This car has 20 coats of hand rubbed lacquer." "Hand-rubbed" was the term in some areas for color sanding by hand. The thinner in the paint was stronger (slower evaporating) than the thinner used in the primer. When you painted lacquer paint, the thinner would soak into the primer and cause it to shrink back into the scratches in the body work. That is why the process was repeated until scratches didn't show in the final coat. Sorry about all the text, Nads, but I thought this would be good companion information to the post. I'll add some more related info later. overspray

[Judd]

Overspray
Thanks! Great post and right on time for me I'm in the act of sand blasting now. can the bondo be thicker if it is done in several coats and allowed to dry in between? I have a spot on my 56 that is cracked and it looks like a dent was covered with about 1/8th" of bondo can I cut this out with 80 grit on my grinder, finish with 80 grit on my DA sander and redo with a couple coats of bondo or will it need to be hamered out? Thanks!
Judd

[timebandit]

Great post. I have one question about using filler on bare metal though. I know most bodymen does it that way but i have allways been a little skeptic about that. I thought rust preventing primer will not have a mission on top of filler.
It has to have contact with bare metal to do its job.
I can see that you will get a long lasting paint job if the metal is absolutely rust free and dry. But can you always be sure of that? The tinest crack in a seam or small pores in a weld can leak in moisture eventually.And then you need the chemicals in the primer to prevent rust. Does modern fillers have those chemical qualities?

I live in a cold salty climate , so rust is always the biggest problem here. http://www.jalopyjournal.com/ubbthreads/images/graemlins/smirk.gif

[Tinbender]

Best information I've ever seen on the subject. Thanks Overspray. You guys that are trying to learn filler, should print this out and study it till you can recite it.

[overspray]

Judd, 1/8 inch is usually no problem for filling. I've seen some really thick sculpting in my day. Building up an area in layers of 1/4 to 3/8 inch will work. The thicker the filler the more chance you can have problems down the road. I have seen jobs over 2 inches thick last for years and some of the old custom jobs were done even thicker. If you have a crack in the metal under the filler, that will have to be welded first. Any place under the filler that can move will show up later. Body filler will have the ability to flex some, but a crack in the panel will eventually crack the bondo. Grinding with 80 grit will work-coarser (36 grit) is OK. Remove all of the old filler and start over using the process I described. If you have trouble getting areas ground out, use a wire brush in a drill or even a broken 1/8 inch drill bit will get into tight areas to grind to bare metal. overspray

[Nads]

overspray, I've learned a bunch from you, junior member.
With all the extensive body mods I've done on my '54 Chevy I should've gone heavy on the filler in the first place. It seems you're right about roughing in the bodywork with 36 grit followed by 80, anything finer does nothing to straighten out the panels. Most of the crap gets sanded off anyway.
I'm following your advice now, although I'm not bondoing on bare metal, it's too late for that. But I am going over catalyzed primer, Nason brand. Everything's coming along really good and I feel like I'm making some real progress, but the goal of having my car painted still seems a ways off.

Every small step is a step in the right direction.

Thanks for your advice.

[overspray]

timebandit-preventing rust (or moisture) from forming under the bondo/body filler repair is a big concern. In humid and cool conditions I don't like to start exposing (grinding) the panel bare until I'm ready to do the filler work and can complete the area to the priming stage. If I have bare (rusty old car) metal I sandblast and grind just prior to doing the body filler work. Keeping the panel warm will keep moisture from forming on the surface and help keep the curing process of the filler even. Temperature is the most critical factor when working in cool humid conditions. There are 2 basic primers to protect from rust. Rust inhibiting primers seal the area from moisture but DO NOT chemically react with the rust. Etch primers contain an acid (usually phosphoric acid) and chemically etch the metal (the acid converts the Iron-oxide (rust) to Iron phosphate) and the filler part of the etch primer seals out the moisture. Phosphoric acid slows down the catalyst (hardner) in the bondo/body filler and can make it not cure properly. Todays body filler/bondo technology basically does the same job on bare metal that a rust inhibiting primer would do. It bonds tight against the surface of the metal ( with mechanical adhesion) to seal out air and moisture. Actually the technology in the bondo/body filler products we use in the U.S. came from Europe so you have had them for about 8-10 years longer than we have. There are no chemical reactions with the body filler (polyester resin) and rust. You could still prime over a small layer of rust, put bondo/body filler over it and end up with problems later. As I said in my original post I use etching primer on bare sandblasted metal but I grind it off in the area I do my filler work. I try to keep the area warmed, clean and dry. By the way, my Grandparents came from Norway. They were lumberjacks and farmers. Maybe we are shirttail cousins. overspray

Overspray.. I was once told not to mix filler on cardboard. Don't remember why. Is it bad to mix on cardboard? I use a peice of lexan and clean it with a razor blade before it kicks.
Clark

[overspray]

So What-The reason you shouldn't use cardboard is- you don't know where that cardboard has been. Really I use a product called "clean sheets" which is a palet with a tablet of nonporous paper sheets that I can tear off and throw away when I'm done. Most cardboard is porous and will absorb some of the solvent in the resin (styrene) but most of all the styrene will let loose any chemical that was already in the cardboard- like if it was a box that held oil, grease, or worse SILICONE!! (armorall) I saw a guy mix filler on an Armorall box once. When he went to sand it with an air board sander it peeled right off. Not to mention he and everyone else in the shop had "fisheye" problems for about 3 days. I still use cardboard if I have to, but Lexan, plexiglass, or an old car door glass is way better. I hope I'm getting smarter in my old age. Like Nads said- I'm a junior member. (Where did all this gray hair come from??? Must be---overspray)

[Humboldt Cat]

Great post, Overspray- learning about body filler and primer is quite a class in Situational Chemistry; it seems to depend what it is yer working with, and/or what order you've done things in. That said:
Been prepping my truck since Fall '02, sanded everything down to bare metal with 60 grit, aircraft stripper for the rest, the brunt of the filler work on the cab 'n front fenders happened over summer, the climate was perfect, it worked out well.
Had to give the garage back to the friend, project's been tarped with baths of metal etch every other day since. Just trying to get everything clear for etching & filler primer, but what an uphill battle (otherwise it'd be primered by now, o'course). Simply don't have indoors for it, right now.
I don't have any primer 'neath the filler, it's either bare metal, bondo and Loctite rust neutralizer, on the surface, respectively.
When a helping hand covered the filler areas, too, with Loctite, it made me wonder if this would 'hurt' the bondo (it's way past the curing stage, though.
Quick question, too, about:
[ QUOTE ]
Todays body filler/bondo technology basically does the same job on bare metal that a rust inhibiting primer would do. It bonds tight against the surface of the metal ( with mechanical adhesion) to seal out air and moisture.

[/ QUOTE ]
Does this mean a lowered chance of new rust having cropped 'neath in, in all this time?
The metal was in excellent conditions when the filler was applied, and have done so much surface/deep rust removal from the bare metal, sometimes worry about what's going on with the metal 'neath the Bondo.
There's so much filler work done, re-doing it doesn't seem like an option. Am covering the cab with etching & filler primer. Just wondered if I was on the right track. Thanks for yer time, man.

[overspray]

Humboldt Cat-sounds like you're on the right track. It's not the best situation to leave the body and filler areas bare for so long, but with projects it is sometimes the only way. You California people have it lots better temperature and humidity wise than the Norwegians and us NoDaks. There are 2 basic self etching primers. Vinyl-wash primer is a thin, vinyl-resin based primer with a phosphoric acid activator/reducer. It is translucent and mostly used for bare metal only (not over filler/bondo) and is usually primed and painted very soon after it is applied (wet on wet). The other etch primers are milder, acid wise, and have some filling ability and are OK to use over cured filler-followed by a good primer filler/surfacer, usually wet on wet also. Check with the manufacturer on times and which systems (primers) to use. If your project has been "bare" in humid conditions, there is a good possibility of a rust film forming on the exposed metal. A scuffing and cleaning followed by the milder etch primer would be my choice. Unless you have a real wet climate, the area under the filler should be OK. I would suggest letting the body be warm and dry for a few days before priming to help let any moisture that may have absorbed into the bare filler areas evaporate. Most primers have some alcohol in the solvents which will help draw some moisture out. overspray

[overspray]

I gotta say some more on etching primers. They chemically grip to the metal by converting the oxidation (rust). They also do this on aluminum and help in getting the best adhesion on stainless steel also. Metal prep/ metal conditioner uses the same acids to neutralize the rust. You CAN have an adhesion problem if you use metal prep followed real soon with an etching primer. The etch primer won't have enough rust (it doesn't take much) to bond with and will not stick. I have seen this happen. I prefer to sandblast the metal then use etching primer (I'm talking old cars here). It's a lot less messy than using metal prep and you get a good chemical and mechanical bond. Follow this with a good quality 2 part primer filler and you have a great foundation for your topcoat finish (SUEDE or SHINEY). overspray

[YoungGun50chevy]

I have question about bondo that has always plagued me. How much working time are you supposed to have? I've made batches up that were the right mixture by the cans directions, and before I could get it spread out, it started to harden. I havn't had a chance to try your mixing method but I'm still curious about this problem since I usually get comments about not putting enough hardner in from experienced people. For the record, most (all) of my bondo experience is in florida during the summer, so keep that in mind. ALso, how could I extend the working time? less hardner? How much less? I'd love to have enough time to skim coat a door without worrying about it hardening half way through.

[SwitchBlade327]

In florida in the summer time, it won't take much hardener. If it's hot out, use less, if it's cold use more. I did the same thing the first summer I used the stuff.

[overspray]

YoungGun50Chevy--Switchblade327 is right, but you can put too little hardner in the mix and it won't have enough to full cure the whole mix. Temperature is the KEY. If it's 90 degrees F out or hotter you will probably have to do the work in the shade and work on smaller areas in order to keep up with the fast cure. You can only slow it down so much or speed it up so much, it has a limit on each end. If you ruin a batch-throw it away! It's cheap stuff compared to ruining a paint job down the road. One thing I noticed the 1 time I was in Florida---the body shops had HUGE airconditioners. We only have HUGE heaters up here in North Dakota. I'm sure it's common where you guys live to have an airconditioner even in your home workshop. The temperature is directly proportional to the amount of hardner and it just takes time to get it "dialed" in. Also ALWAYS mix the batch as thouroughly as possible!!! Not so many years ago our neighbors in Canada used clear liquid hardner for thier bondo/body filler. That is really a pain to use when you can't see the color change like with the creme hardner we use in the States. overspray

[Humboldt Cat]

I keep seeking out this tech post, it's been so damn helpful.
[ QUOTE ]
You CAN have an adhesion problem if you use metal prep followed real soon with an etching primer. The etch primer won't have enough rust (it doesn't take much) to bond with and will not stick. I have seen this happen.

[/ QUOTE ]
Wish I'd read this before etch primering, today. The Loctite rust neutralizer 'cured' well, no surface rust patches in it. To be on the safe side, I wiped the rig down with metal etch before primering. I didn't have a lot time to work with, today, especially after the electric air compressor I was renting was causing the fuse switches in the condo to pop shut (the worst was when it happened with the garage, affecting ALL condo garages connected to it).
Switched with a gas powered air comp and the etching worked well. Didn't have time to put the filler on, but will finish up the etching and then filler tomorrow.
Thanks for all your info and help, Overspray! Hopefully I did it right, today.

[Humboldt Cat]

Afterthought- I know my reply wasn't so much about Bondo itself, but you've help clear up alot of question marks about the type of primers I'm using, in conjunction with the filler, and, hell- bodywork history. It feels like a big push forward, though. Viva la HAMB for posts like this.
I'll have pictures soon- got so much help from Polly's teen boys, Luke in particular had fun taking photos of the whole thing happening. What a trip. Thanks again.

[TomH]

Hey Overspray, I was going to bing up your old post, but this is working out much better. Lucky for me your only a phone call away. Oh yea that aint overspray, it's GRAY HAIR http://www.jalopyjournal.com/ubbthreads/images/graemlins/smirk.gif

[Plowboy]

Overspray, since this got back to the front and you worked with the evercoat people, what is the difference between Rage, Lite, Z-grip and any of the other evercoat fillers? Is there a specific use for each one?

Should you mix them (by this I mean layer)? I figure if you are using layers of different stuff there will be different layers of hardness making it a real bitch to sand anything out level.

[overspray]

Plowboy--rage is a top of the line filler ( my personal choice) Z-grip was introduced to stick to galvanized panels (80's and 90's Ford pickup cowls for instance). The lite weight filler was a price leader-still good stuff. Mostly it is pretty much what you like and how you percieve it works for you (personal preference). I like rage filler and metal-glaze liquid glaze putty. Most filler companies have good products but things have really improved in the last 15 years. The resin in rage was a major accomplishment in the technology of adhesion and workability. A big part of the development was due to base-clear paint. You basically double the amount of solvent you put on a paint job from old single stage paints. With the older fillers and primers all that extra solvent would cause the filler areas to leave a stain-like area that would show up in the paint. Some changes were made and new products evolved. All the old guys who worked with bondo 30 years ago will agree it's really nice to have the products that are available today. Some of the old body fillers were like sanding an Interstate Highway. Still the major factor in body work is 2 part primers and finishes. They cut the work/dry time down drastically and give us 20 times the durability and way better appearance. I hope some of you reading this post add a few pictures of your work (I'm still learning the photo thing). Nads has some real nice work in progress pictures (I see major artistic talent there) and I'd like to see more from some others --60's style--Humbolt cat-- to the digicam. Tomorrow I'll post some more primer info that should compliment the information here already. overspray

[Humboldt Cat]

[ QUOTE ]
and I'd like to see more from some others --60's style--Humbolt cat-- to the digicam.

[/ QUOTE ]

I dig it, it's like the Bat Call for the Bondo Brigade, or somethin'. I'll have some pics for you when I get home from Work...

[Paul]

this is a great post, this stuff is what makes the HAMB such a great place!

so uh..here's where I'm at,

I sand blasted the body inside and out and used DP90 on the outside and POR15 on the in and under sides.

'threw it all together and drove it for a year or so.

I started the bondo a month or so ago with the intent of driving it this summer with real paint on it.

to add to all the great info already is tough,

one thing I would say is lighting is very important, especially if you work inside.

for large areas I set up a work light so that the light shines across the surface highlighting all the high and low areas.

I work in thin layers slowly working towards the finish shape as oposed to laying it on heavy and carving it down to shape. just seams to work for me.

I have found that when I do pile it on if I wait till it's good and hard it shapes very nicely with a wood rasp, it would be good to have a few with various shapes and sizes.

It's also important to be able to stand back from your work to actually see it, if you have a small shop roll it outside once in a while.

daylight can also reveil stuff you can't see inside.

anyway here's a couple snaps,

http://photo.starblvd.net/~60s_style/4-1-1.jpg

http://photo.starblvd.net/~60s_style/4-1-2.jpg

http://photo.starblvd.net/~60s_style/4-1-3.jpg

http://photo.starblvd.net/~60s_style/4-1-4.jpg

http://photo.starblvd.net/~60s_style/4-1-5.jpg

Paul

[Humboldt Cat]

Thanks, '60s, ya helped me figure out where to start with this (but not go too long on it). I haven't figured out how to string multi pics in one reply...
After sanding off all the old primer, paint and LOTS of bondo, and celebrating no signs of rust or rust holes underneath, I began putting filler back in, focussed first on the doors, the bulk of the filler work done in a friend's garage between January and August of last year.

[Humboldt Cat]

Took me forever not only to finish this fender, but figure out the finesse of good mixes and no pinholes. This is before I discovered red hardner, which works better for me. Meanwhile I POR-15'ed everything beforehand. This is from Feb. '03

[Humboldt Cat]

Closer one... Last Summer...

[Humboldt Cat]

Was tricky for this amateur to get the roof even...
Summer '03...

[Humboldt Cat]

After various hurdles that put the project on hold, I'm still at it last November... constantly at it with metal etch. At first I mistakenly decided to wait 'til ALL the corrective bondo work was done. Then it became more apparent my outdoor project should be covered in primer ASAP (sins of a beginner, helped by HAMB'ers).

[Humboldt Cat]

Filled the cab corners, kept the doorjambs paintstripped and the rust away...

[Humboldt Cat]

Perfecting level planes on the front hood... (rubbed out the 8-month old primer last week, worked around the bondo)...

[overspray]

SUPER PICTURES!! That's just what I was looking for. Also great info on working batches and layers. Thanks 60's Style and Humboldt Cat. Your projects are NOT in the beginner class. The work looks exceptionally good! Your projects and Nads are tributes to the talent of the people who hang out on the H.A.M.B. I LOVE IT!!! overspray

[Humboldt Cat]

Glaze putty for touch-up on the front hood, where I'd smoothed over the center emblem holes... gf's son Luke did that teardrop (just below the blanket) out of a big lump o' bondo.

[Humboldt Cat]

Glad you like 'em... '60s is right, it's hard to summarize it. My attempt at etching primer didn't work out, last month (when this shot was taken), so I rubbed most of it out, rust-neutralized the body and shot it again (with a MUCH better air comp) the other day. Got the etching in there... and then the next day it rained. Waiting for the weather to clear before filler primer.
Thanks for all your help on defining the differences in primer (mine's Transtar self-etching, not epoxy), it helps to figure out how best to proceed, considering the elements (had I garage to work with).
That's it for now- hey cool shots, '60s Style! How recent are those?

[Humboldt Cat]

One more for the road... aside from the front fender, this part around the gas filler neck has been trickiest, because of the spacing, a classic teacher in different ways to work your hand or block for an even sanding. That's all.

[Paul]

[ QUOTE ]
'60s Style! How recent are those?

[/ QUOTE ]

I took those pics this morning at about ten o'clock.

overspray, thanks again for the info &

Humboldt Cat, looks like you've come a long way, lookin' good!

thanks for the kind words guys,

now where's Nads' current pictures?

you find your camera yet?

hey, maybe soon we'll have a PAINT TECH post??

Paul

[overspray]

PRIMER INFO--I'm going to mention types of primers and not so much specific brands because everyone will have different brand names available in their area. --Timebandit-- I hope you are still following this post because you brought up some very good questions and concerns I want to address. I'm a firm believer in the 2 part primers. There are so many kinds and I'll try explain the basics of most. Urethane based 2 parts are probably the most universal. They are based on resin that uses an isocianate hardner (health concern here). Most epoxy primers are 2 part based on epoxy resins. Polyester primers are based on polyester resin (fiberglass/bondo resin) and use the same chemical as a catalyst as fiberglass and body filler. These primers all bond with mechanical adhesion--they grip to scratches in the surface of the panel (metal-fiberglass-plastic-bondo-etc). Self etching primers use an acid based activator/reducer to convert with the metal and form a chemical bond as well as mechanical adhesion. For resistance to moisture both the type of resin and the amount of solids (filler material) in the type of primer are factors. A good 2 part resin that provides good mechanical bond along with dense filler material that does not absorb moisture will be better as a rust inhibitor. There are some really good systems available in everyones price range. You should do some research and ask questions about the system you are interested in and make sure to get thorough product information reference sheets to insure you use it correctly. In the product information for any particular primer, it will tell you-what kind of surfaces it can be applied to-how the surface should be prepared (sanding/cleaning)- how much it fills per coat (mill thickness)-what chemical or solvent resistance it has-and what topcoats should be used. READ these and ask questions if you don't understand. Most companies have a web site or an 800 number you can reference. You will find a huge variety of primers for filling and sanding-sealing and protecting. Another thing I really like that both 60's Style and Humboldt Cat referred to is POR-15. Sealing the backside of your panels and neutralizing corrosion on the inside will make the repairs last so much longer. Moisture can seep through tiny pinholes and ruin your body filler repair or primer and paint. POR-15 together with a paint or under coat can probably seal most tiny pinholes in the panel. I don't know if it is possible to get them all but this is a good way to start. In areas where panels have been welded I like to seal the inside of the weld with POR-15 and maybe a layer of seamsealer and paint. One thing on DP primers. If used as a rust inhibitor read the tech sheet to see the mills (thickness) per coat. These primers are usually used for tie-coat sealers and should be topcoated with another product. For use as a "storage" primer you may need several (more than 2) coats to get good moisture protection for an extended time. overspray

[Humboldt Cat]

Haven't used POR-15 as much lately, have been mostly doing metal etch and Loctite's deep rust neutralizer. Initially got the front part of the truck good 'n plenty with POR 15, but not with the other half (still time to do that with the bed and rear fenders, though). My help recently went as far as to cover the bondo as well as the bare metal with the Loctite, am not sure if that would help or hinder things. 'Neath the primer the whole cab's covered in Loctite, just to be on the safe side. Is this good or bad?
I'm glad yer progress on to primer, since (of course) that's what the project's evolving into. Also, you'd mentioned doing POR-15 on the inside as well as outside of the panels, hadn't thought of that, I've only done it on the outside o' the panels. Well, what's done is done, we'll see from here (at least for the cab).

[overspray]

Humboldt Cat--if I remember the directions on both the Loctite and POR-15 say it is OK to put body filler/bondo over it after it has cured. You should be doing everything according to the specifications. The pictures of your truck are exactly what REAL "Magic dent erasing" is about. overspray

[timebandit]

Yes Overspray, Im following with great interest. http://www.jalopyjournal.com/ubbthreads/images/graemlins/smile.gif
I`ve always thought there is a chemical substance in all rust inhibiting primers that protects the steel from moisture.Even when cured. I have noticed that steel surfaces with primer only will rust after a while.
I have also noticed that bare steel with just automotive paint and no primer will rust fast. I therefore reasoned that no paint is absolutely sealed and will have pores on a microscopical level.
But the combination of the two will last for decades if taken care of. Then there must be a mechanism in the primer that takes care of the moisture that seeps through the pores in the top coat.
One other thing. I have had some problems with long lasting finish on sand blasted parts. Even with two coats primer, two coats paint and clear on top I have had rust showing through the surface after a while.
I belive the cause of this problem is that the primer sinks down in the "valleys" of the pitted surface and the "peaks" are left with almost nothing. Next time I will sand the surface first, and then again between coats to be sure everything is protected.
At least in this part of the world the main problem of getting a long lasting finish is rust and not adhession. Most of the time I have noticed loose, cracked bondo it is caused by rust on the surface beneat.
You have some very good recommendations on sealing the back side of the panels.Thin penetrating rust inhibiting oil is good in hard to reach places such as doors and rockers.
Where in Norway did your family come from btw?

[overspray]

Timebandit-- I wish my Norwegian was 1/10 as good as your English. I'm amazed how well you command and understand American English especially with the technical information I giving. One part of my family came from Numedahl (Numedal) and my Grandfather (Dad's dad) came from Sogn North of Bergen. I know I have relatives in Bergen but I haven't corresponded with them or even met most of them. Back to primer and rust. In the opening of this post I mentioned pre-WARMing (NOT HOT) the panel in cool humid conditions (which you and I both share because of climate) to evaporate the moisture that condenses on the metal. The metal will be 10-15degrees Farenheit cooler than the air and moisture will condense on it. If you put filler on a cold panel in humid conditions you trap a thin film of moisture under the filler. That is ONE of the causes for rust under the filler. This is the easiest to avoid by simply warming the panel to slightly above the air temperature (which should be above 70 degrees F.) Grinding or sanding the panel just prior to applying the filler will also help. When spreading the first batch of filler to the bare metal, extra pressure should be used to force the material into the metal as thoroughly as possible. This helps the mechanical adhesion of the filler to the metal. An even cure temperature until full cure is reached will also help with expelling solvents and humidity from the filler as it cures. You are on the right track about primers. The material most used for rust inhibiting and protection against moisture is Zinc-Chromate. This material has a large molecule that is dense and when used as a filler material in primers helps stop moisture from penetrating. There is a health concern with chromate based products and we are starting to see "chromate-free" products. Lead based paints give the best protection but due to health concerns they are being replaced with other less dense materials. Most old and probably new ocean vessels are painted with lead based primers and paint to ward of the corrosive effects of salt water. When you are buying primers compare the weight of the can. High solids primers may weigh up to 5 pounds more per gallon. Always read the information sheet to see if what you are buying is right for the job you have planned. I like self etching primers on my sandblasted (old car parts) and yes, sanding the sandblasted steel to smooth out the high spots is a good idea. The etch primer's activator (acid) chemically bonds with the rust to form iron phosphate. If I'm not doing body filler work soon I leave this primer on for protection. For really long term storage I use a dense urethane 2 part primer on top (wet on wet) per manufacturer's directions. When this is fully cured I prefer to grind, the areas I am going to fill with body filler, to bare metal. I could actually put filler over the FULLY-CURED primer system (after sanding and making sure it's clean) but I usually find some more metal finishing I can do and it's easier to grind that area off to do the work. If I have areas that are bare for a time in between work sessions and surface rust seems likely, I use a small sandblasting gun to re-clean the areas. I hope this information helps, but everyone reading this has to do some research themselves on the specific products and systems they are going to use. overspray

[timebandit]

Thanks Overspray. I have actually never been in an english speaking country.( will be soon, heading for Paso this year) but we learn it in school from early age on. But I think Ive learned most from american car mags and books tho.
So infact I find the technical terms somewhat easier than the casual slang often used here. But Im learning...
Thanks for clearing up the primer/ bondo issues. I think I understand the procedures now. http://www.jalopyjournal.com/ubbthreads/images/graemlins/smirk.gif
-Thomas

[curbspeed]

Overspray, I, like probably alot of us, Would like to thank you. Your info is really appreciated. I am just getting started with bodywork. I planned on using Vari-Prime on all my baremetal first. Can I use the Rage filler right over it? Do I have to wait a certain amount of time or can I start to use the filler right away. I have a fairly pitted frame that has been blasted and I wanted to attempt to hold back any rust if possible. Thanks for being so helpful with rookies like me.

[side_valve]

Fantasic post - many thanks!!

[Fatstang]

Overspray: Excellent tech post. This has to be the most concise and well written post I've seen on the subject. It seems like everybody I've talked to in the past has had a different opinion if to lay the filler directly on the sheet metal, or over the primer, but offered less then stellar reasoning for their point of view. Your explanation lets me understand why there are divergent views, however your recommendations sound extreamely sound to me.

[Tinbender]

BTTT

[overspray]

Curbspeed, the Vari-prime has an acid based reducer/activator. You should NOT put the Rage over the Vari-prime if there is any chance it is not fully cured and the acid has not completely converted. This is hard to determine in cooler and humid conditions which slow the process down. I like to let it dry, then before I apply the filler I remove the Vari-prime by grinding the area first. This also gives better mechanical adhesion for the filler. Another option is a rust encapsulator like POR-15 or similar product. Clean or sandblast the rusty areas then apply the POR-15 (or similar product) let it dry per product information and rough the area up and apply the filler. Anytime you apply filler over something that has a solvent (thinner/reducer) base it has to be dried and cured enough so all the solvents are evaporated and still roughed up with abrasive. There are solvents in the filler that could soak into the layers underneath and cause shrinkage later. Self etching primers (acid based reducer type like Vari-prime) are still soluble and can absorb thinner or solvents. Thin layers, maybe 1 coat, will be less likely to cause problems. Thick layers, like multiple coats, can act like a sponge to soak solvents which can remain until after the filler cures, possibly causing problems later on as they try to escape. So even with this information, the best is still to apply the filler directly on the cleaned (sandblasted-wirebrushed-abrasive ground), warm, dry bare metal. overspray

[thatredcaroutside]

I usually apply a coat of Fix-a-dent to the damaged area at night before I go to bed and the next morning the whole dent is usually gone except on the really deep ones they will need a second coat.
I also like the minty taste of Kentucky Jelly on my biscuit or toast for breakfast.

[curbspeed]

Overspray, Thanks! I'll take your recomendation. Keep this thread going if you would please. I realize you might have to repeat some of the same info a couple of times but this stuff is helpful. Dale

[hemi]

Well done!

Many great tips, and the unravelling of a few urban legends.

Thanks!

[visor]

Overspray... What are the correct sand paper grits
to use from prep of the bare metal to working down
the filler, applying the primer and before final color.

Also what do you recommend for a suede finish?

Great read!
TIA,

[overspray]

A lot of the sandpaper grits are a matter of preference. Basics are: 16 to 36 grit for grinder discs for paint removal and bare metal bondo prep- 24 to 36 grit for roughing out the filler with an air file sander or hand board- then 60 to 80 grit for smoothing out the rough scratches from the previous operation and shaping finer contours-then 80 to 180 for further smoothing in preparation for "high-build" catalyzed primers (with hardner)-or 240 to 320 grit for lacquer based (non-catalyzed) primers-320 to 600 grit for final sanding prep before paint, following the manufacturers guidelines on their product information sheet-and finally 600 to 2000 grit for sanding clearcoats for recoating clear or removing minor surface imperfections prior to polishing and buffing. PLEASE-ANYONE ELSE CAN DIVE IN HERE WITH GOOD IDEAS AND TECHNIQUES. The last shop I worked in was a Cadilac/Oldsmobile shop and we used AKSO-NOBEL/SIKKENS paint and primers. This is high dollar top line product. Our production system was- bodyman finishes the filler work to 80 grit- then a quick trip over the filler and old paint edge with 180 grit on a DA sander (lightly to not destroy the shaping)-then featheredge the surrounding repair with 320 Grit DA sander-red scuff pad (scotchbrite) a little past the area to be primed-prime with 2-4 coats of high build catalyzed urethane primer- after the primer is cured any areas needing slight block sanding are done with 240 to 320 grit on the primer-then use a "finishing DA" sander with 320 grit on flat surfaces and 320 to 400 grit DRY sanding on most of the rest of the repair-for Base/Clear paint the rest of the panel was "wet scuffed" with an abrasive cleaner/sanding paste and a gray scuff pad (scotchbrite)-certain colors, mostly some types of metallics, would need a little finer prep on the primer area, maybe 500 to 600 grit light wet sanding-then clean-mask-sealer (a lot of times not necessary with this system)-and paint. For those of you not familiar with a finishing DA (dual action orbital) sander, a regular DA has a slightly bent shaft that helps cut better for featheredging and removing paint. A finishing DA has a straight shaft and with practise produces a very smooth and flat surface without waves or ripples. Now, my favorite suede finish is a very good quality single stage urethane enamel flattened to about 75 to 80 percent. Some colors won't stand up with this much flattener in the mix, so some experience with the pigments used in the mix is a must. A big part of the durability in any paint system is in the undercoats (primers). overspray

[williebill]

Overspray,I'm sorry to repeat what so many others have said,but DAMN...this is great stuff..Tried printing it all last night,ran out of ink,tonight the printer is cutting the ends off of all the lines,so I've spent hours reading,and writing in the missing words..Worth every minute of it ! I've got body/paint books and articles from the 50s til today,tons of them,and your info is the best I've ever read.THANK YOU for spending what has to be shitloads of time typing this for all of us.
My wife will cook,and you can have the kids room whenever you need to get away and help me do the bondo work on my Merc.OK,you can have the wife,too http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif

[Roadsters.com]

Reed ("overspray"), you are a real asset to this place. I've saved your posts on this thread because you've given us a lot to digest, and this information needs to be understood by everyone who does bodywork.

If Ryan has no intention of saving this thread in his Tech section, I would like to ask permission from him and yourself to put your posts in this thread as an article credited to you on my site, http://www.roadsters.com/

If you don't mind, I'm going to paste another of your posts (from the Fiberglass Horror Stories thread) in here as a way of keeping this thread from sliding off into oblivion.

Thanks for taking the time to share your knowledge with us. Here's your post on fiberglass.

Quote:

A friend of mine was restoring an old Corvette and the owner opted to buy a one-piece front end and then install the bonding strips to make it look original. I can't remember the company that made the front end, but it looked nice when it showed up. The installation went well, and the paint looked real nice. This was in late winter early spring. The first time the car got some serious sunshine the seams and thicker areas of the glass started to bubble. He thought it was the paint, but when we inspected closer and I made a couple calls to my mom's cousin's husband (who has a Masters degree in industrial plastics), it confirmed what I suspected. The part was laid up in January (cool shop temp, probably below 60 degrees F.) They must have heated the outside to set it up, but the resin didn't reach full cure inside. After sitting in the sun, some of the curing process continued, which expells styrene (a powerful solvent in polyester resin) and gasses, and caused bubbling in the areas mentioned. It was a mess!

Fiberglass resin (polyester resin) is basically the same as what's in bondo. In pure form it is like water, but usually the stuff we see is like syrup because it is thickened to make it easier to handle. The same basic ingredient (MEK peroxide) is used as a catalyst in bondo and fiberglass resin. Mixing the correct ratio of liquid hardener to liquid resin is difficult and you need practice and experience. Temperature is extremely important!! Below 64 degrees F the resin won't cure properly with the correct ratio of hardner. You can add a little extra hardener but too much and it cures unevenly and can trap gasses and styrene in the part or crystalize the resin and make it brittle. Over 95 degrees F. it cures real fast and thicker areas can easily cure too hot and crystalize. It starts crystalizing over 140 degrees F. It's best if you can work between 75 and 85 degrees F. (the temperature of the mold or part), maintain some air flow, and the correct hardner ratio for a nice slow even cure. Different companies thicken their resin in different ratios, which proportionately affects the hardener ratio. It takes years of experience and knowledge to get real good at this, and the best "glass men" will screw up a batch.

[Tman]

This needs to be saved in the Techomatic!!!!