MartinSr,Sevn-ty,how about some basics on body filler application...Mixing,spreading,sanding,and maybe primeing b4 and after...

I'm thinking alot of it is just trial and error but I sure have alot of error all over my floor in my shop :(

When do ya go from say a 80 grit to a 150 when sanding the edges?

Seems when I mix some filler up I always have it set up to fast even when I seem to use less hardener :(

Is it best to use an epoxy primer under the filler then use a 2k primer over it?

If you'all have done a basics on this topic b4 I apologize,and will search the topic ;)

Thanks for all insight on this site,I for one enjoy reading all of your info from you both!! :D

graemlins/waving.gif
Rick

Your wish is my command Rich.
This is actually the second "Basics" and I was planning on doing a "refresher" on it last night, but I fell asleep. Us "old" guys can only hang on so long after a hard days work. smile.gif

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>Plastic filler basics;

What ever tools you use the trick is to not add the last "skim coat' till you KNOW that it is all you need. Don't try to block out that first coat, just use it as a base for the LAST skim coat.

I was taught this procedure after doing bodywork for a number of years and it really works well:

Just apply a nice coat of filler (what ever brand, whatever style, we will put that aside right now). Cut that coat NOT to make it perfect, but to get the basic shape and filling you need as a base for the skim coat. You can cut it with 36 40 or 80 depending on how big the area you are working is. In other words, if you can cut it fast with only 80 then do it. But I would say that this would be limited to an application that is no larger than about 8 inches.

If you happen to have a few high spots, see if you can tap them down.
If you have a few low spots add a bit more filler to ONLY those spots.

Re-cut these last low spots you have just filled with the same grit you have been using (most likely 36).

If you now have a surface that ONE skim coat will fill, then apply it. If you don't work with it a bit more, but NEVER add a little here or there and think you will finish it without a skim coat.

If you have a surface that is very close with only a few VERY MINOR low spots like poor feathering onto the metal, poor transitions from one application of filler to another, or from the metal that is "poking" up here and there you can do the LAST skim coat.

This skim coat is very important, you want it to extend over the COMPLETE area, this is well past the damage you have been working. Maybe as much as 3 inches past the plastic that you have applied to "rough" it out.

This skim coat can be regular filler or a polyester glaze like "Icing" or "Polyester glazing putty", that is your choice, I use both depending on the size of the area being worked. Do not use anything that doesn’t mix with a hardener. NO, “Spot putty” in a tube, only polyester putties or fillers. If it uses a hardener, it cures to a hard film. The “spot putties” stay soft and can become even softer when the solvent from the primer coats it.

You now run a block, long board, or hog even over this skim coat with a little bit coarser paper than you plan on finishing with to cut off the resin that has surfaced in the filler. I usually just use the 36 or 40 or whatever I have been on the "rough" work. BUT take CAUTION not to cut much off, you want to JUST take the very top, don't really sand AT ALL.

Now finish sanding with your longboard or block or hog or whatever using the finer paper like 80 on a large area or 120 on that small 8" sized area. Block it out to perfection with a nice feather edge to the surrounding metal.

I can't stress enough, the trick is to know when just ONE LAST skim coat will do the job. And apply it COMPLETELY over the surface. If you only one little low spot in the middle, DON'T just do it, skim the ENTIRE thing. You HAVE to have one LAST skim coat over the ENTIRE thing every time. If you get in the habit of this you will do it over and over on every dent you repair and find that you can do just about any dent with just
two applications.

As you sand the filler let the board or block you are using run over the surrounding metal. If you only work on the filler you will sand it too low. You need to keep it as high as the surrounding metal, so use the metal as sort of a straight edge that you run the block or board off of.

Don’t worry if you cut through this skim coat here and there. In fact, you WILL most likely cut through. The point of that "LAST SKIM COAT" is that after you add it, you don't add ANY MORE filler. That "LAST SKIM COAT" is just that the LAST filler you add. If you hit a little filler below, or metal, that is normal and fine. The only thing you are looking for at that point is if the panel is FLAT. The filler skim coat is serving no other purpose than to finish you filler work, it is not a "sealer" or anything like that.

You can add fiberglass resin (“A” coat if you have a choice) adding the resin was exactly how I learned from the great Emery Robinson (my personal hero in the auto body world). But remember there was no products like polyester putties back then. When you add resin, that resin comes to the top of the film of filler. It is then something you have to deal with. The whole purpose of the SKIM COAT is to put a layer of filler over the top that is easy to block out with as little effort as possible. You want to be able to concentrate on making the panel FLAT not fighting with gummy resin, sand scratches and the like.

So the polyester putty though expensive is what I use.

How is this for an idea, a co-worker of mine showed me this very obvious tip. smile.gif

Add pour-able polyester putty to the regular filler! What an idea! LOL A little pour-able squirted into the "bondo" really thins it out nicely.

The "LAST SKIM COAT" should be left to cure a good long time. Where you may jump on filler and sand it as soon as it is hard, the skim coat should be GOOD AND CURED for an hour or more. If you can of course, in the production shop you may not be able to wait that long. The benefits of the procedure will not be diminished.

A little added note, I have found that I don’t use 36 or 40 grit at all anymore. I went to work at a shop that didn’t use the coarser grits so I had to learn not to also. I have found that using just the 80 and then finishing the Skim coat in 120 or 180 works great, even on large panels.

At this shop it was the first time that I wasn’t doing my own primer work. This meant that I couldn’t “cheat” with a lot of primer and blocking the body work “one more time”. I found that I had to get the work PERFECT, then give it to the painter. I did this in an interesting way, I look at the last skim coat as even a more “final” step. I now look it as “primer”. You see I have used polyester primer, which is like spraying “bondo”. They are both polyester resin based and act and sand very much the same. So, I figured why not just “spread out my primer” as the skim coat! It has worked GREAT, the painter jokingly says, “do you think I’ll need to prime this or just paint it?” I tell him, “Just clear it, it’s a shame to hide that work under primer”.

This method has worked great for me, it’s more of a state of mind than a procedure.

And don’t be afraid to buy the best sand paper and use a lot of it, the cost of the paper will be nothing next to the time and muscles saved. Find the paint store in town that services the PROS the Body shops in town, that is were you will get the right stuff and the right info.

Thanks MartinSr,I have recently been doing searches on your basics of basics and have printed out anything I could find. Im starting to get a nice collection in a 3 ring binder on things like body/paint work. As with many others here your contributions go above and beyond. graemlins/beers.gif

Originally posted by flywheel:
Sevn-ty Not sure if this was for me or not but I;ll open my pie hole anyway :D

WELL the first thing I should say is there is more then one way to skin a cat, there are several methods out there that will get you to the same place, its just how they get you there. Plus its been a long day and I started tipping the bottle graemlins/beers.gif early so pardon my speeling and if I dont make sense

Martin pretty much covered the filler part, i didnt read the whole thing but sorry if he mentioned it but on that FINAL skim coat I knock the filler down with 80 grit then finally smooth it out with 180 grit. The reason is because you dont really want those 80 grit scratches in the filler if you dont have too. The reason is primer can and will shrink, the 80 grit has more area for the primer to shrink INTO then the 180 grit. Plus it doesnt need as much primer to fill 180 then 80 girt.

On the fast filler cure times it cures faster in the summer then winter so less hardner is needed. If you have access to a digital scale or such you can add the hardner by weight. Most fillers go by the 3-4%. Just say the filler weighs 10 grams then the hardner would be .3 grams

Use a premuim grade filler like rage or rage gold. Some of the cheaprer stuff isnt stain free, meaning they are affected by the UV rays. Light colors and blues and most effected by this, the sun will turn the filler a pale yellow tint, very vissable under the paint.

Ok on expoy I dont want to get in an expoy vs etch primer debut, Ive been in several already and not just on this site so JUST KEEP IN MIND this is my opinomn
Etch is the best rust and adhesion primer out there bands down. etch bites into the metal and bonds with the metal molecules were expoy just LAYS on the surface. Not sure what brand you are using but I know for a FACT in both PPG and dupont tech books it stats that when using expoy its best when usng over metal treatments or etch primer. there is a ling to PPG on what they say to correct rusting!
http://www.ppg.com/cr-refinish/phase1/frmShowDefect.asp?LanguageId=4&IntDialCode=44&ProcessStage=0&ShowPicture=0&DefectId=88
Notice is says nothing about expoy, only etch primer.

Now am not saying expoy is a bad product just on bare metal theres some thing better. If i was going to do the filler over peimr methoid, then what i have done in the past is first apply etch prier then apply two coats of expoy. Allow the epony to dry atlest a day or 2. the come back and scuff sand the expoy with 80 grit and apply your filler.

NOw keep in ming ONLY EXPOY CAN E USED UNDER FILLER, etch and 2k cant be used under filler. The chemiclas in the filler will react with the etch and cause the etch to lift if you apply the filler over etch, but you can apply etch over filler, never filler over etch.

The reason filler over primer methid is poluar is because the etch/expoy comb seal the metal form the filler. When filler cures it get hot, this can cause condenstion which can drew in moistuere, espaceially if you applied over some welded areas, as you might have smoe tiny pinholes :(

Primer surfacer or 2K is meant to be used to fill minor surface imperfectiosn not for a corrostion or adhesion aid etc, it just fille minor flaws. Now primr surfacer llikes to shrink womewhat. this winter i did some tesing on PPG's K36 prierm. I allwd it to sit for 1 week and fully cure and shrink. after that week I measuered the beiggning volumes and the ending vloumes and noted is shrunk alomsot 5% :eek: I also saw it started shrinking after the 3rd day, and by the 4 and 5th it really kicked in. The point is allow the primer its FULL cure and skirkn time, even tho it says 4-6 hrs to sand it not done shrinking. If you block it smooth after one day you smooth it out but, later it finally cures and skrinks and now your panle is all wavy aagain. So allow the primer to sit atleast one week then block it out.

I do have tons more inof to give but am out of bozze :( Ill post it later when am sober i guess and more readable...Eric

Thanks both of you guys for your input.Anymore is always appreciated smile.gif

Yes it was for you sevt-chevelle,I just couldn't remember your spelling graemlins/clonk.gif

I have been using evercoat liteweight filler,but the can is down to the lumpy stuff now so i'll invest in some Rage...also some of the polyester skim coat stuff(i believe it's an evercoat product).I'v used a ppg wash primer/then the DPLF epoxy/then the filler...Any need to go back over the filler with the DPLF or just use the 2k primer???
I have used the wash primer THEN the 2k over it on some areas...It's a Marhyde brand 2k primer,it sure sands well and easy smile.gif
Anything wrong with this way of doing it??? :confused:

Thanks for all the help!!! graemlins/thumbsup.gif

graemlins/waving.gif
Rick

Flywheel, am not certain on the marhyde products never used but are you using a primer surfacer or a poly primer? A poly primer would be a heavier bodied primer, ppretty much watered "bondo" but in sprayable form. Some but not all poly primers recommend you NOT to use an etch primer under them. So that might be something to look for on the label of that marhyde!!

But anyway the method of going etch then 2K is just fine. In fact I pretty much do all the bodywork apply filer then apply one coat of etch then apply 3-4 coats of primer surfacer(2K). I use PPG products since that what I learned to paint with and feel most comfortable with. PPG's etch i use is DX1791, they also make dpx170/171. But a bad thing about the DPX series is that on some products you cant apply it under them. DPLF for example only lists dx1791 for a etch, K36 only lists DPX171, so the DPX is not compatiable with all products.

As for a primer surfacer the stand by primer is K36. The great thing aabout this product is that it can be used as a primer, tinted primer or sealer depending on how you mix it. But in my opinion PPG's best primer surfacer is K38 because it fills much better then k36 and sprays better too. The problem i have with 36 is that it has a very short potlife of 30mins, but you can mix it with 1 part reducer to extend its potlife out to 1.5hrs but the fill is below par. that 30 min potlife makes it hard to spray 3-4 coats before it starts to set up. K38 has a longer potlife so by the time you get to that 3 coat it still sprays just like the 1st coat.

For a poly putty I like evercoats metal glaze or Upol's dolhpin glaze which is what we use at work

Originally posted by MARTINSR:

A little added note, I have found that I dont use 36 or 40 grit at all anymore. I went to work at a shop that didnt use the coarser grits so I had to learn not to also. I have found that using just the 80 and then finishing the Skim coat in 120 or 180 works great, even on large panels.


This method has worked great for me, it's more of a state of mind than a procedure.

Well Said!
Ditto.
I'll even block the "skim" coat with 240 to follow-up. I've learned that a bit more time there will save a lot of time blocking the primer/filler. I've had Much Better final results, esp under darker colors, ie; Black.

Originally posted the the lit-up Sevt_chevelle: :D

NOw keep in ming ONLY EXPOY CAN E USED UNDER FILLER, etch and 2k cant be used under filler. The chemiclas in the filler will react with the etch and cause the etch to lift if you apply the filler over etch, but you can apply etch over filler, never filler over etch.

Now primr surfacer llikes to shrink womewhat. this winter i did some tesing on PPG's K36 prierm. I allwd it to sit for 1 week and fully cure and shrink. after that week I measuered the beiggning volumes and the ending vloumes and noted is shrunk alomsot 5% :eek: I also saw it started shrinking after the 3rd day, and by the 4 and 5th it really kicked in.

Ok, I have a couple of observations/questions here.....

You stated that a reaction would cause the etch to lift if bondo were applied over it, but the other way around is fine. From a chemical standpoint, is this reaction then due to an initiator in UNCURED bondo reacting with the etch primer, whereas if the bondo is already cured, then there is no reaction (because the initiator is used up in the cure of the bondo)?

This is the only scenario I can think of to cause this phenomenon........

How did you measure the volume change? Was this done with an Archimedes measure? The reason I ask because if it is just placed in a container, and not applied to a sample panel with the appropiate thickness for the application (as with the Archimedes method), the free volume change WILL be different.

On another note, my neighbor has been getting his truck ready for paint. He used the PPG DPLF 2K epoxy over a patchwork job (bare metal in some spots, filler in some spots, and old scuffed up paint in others). This is what the paint supply house said could be used to seal all that. On top of that the K36 was applied . I've been helping block sand all that out. His brother had used the reducer you spoke of to extend pot life, but I was wondering if that caused some of the dry spray that I saw(or was this just bad spray technique)?

When I do my own car, if I take my time with the filler and skim coats (spreadable primer, as Martin calls it :D ), would the K38 be appropriate, or should I try to use the thinner K36?

Crankshaft

Crankshaft i dont know excatly what chemicals cause the etch to lift when filler is applied over etch. I want to say its the benzoyl peroxide?? in the hardner. When you apply the filler over etch, the peroxide lifts the etch as it reacts with the filler as it cures, but when the filler is applied first and cured you dont have that problem. Am not 100% thats the corect chemical process or reaction,but I know you just cant apply filler over etch, only etch over filler.

As for the shrinking primer, the way I did it was I used a containter with known volumes. For the beginning volume when I mix my primer in the mixing cup it would measure 7 on the cup. So I filled the mixing cup with water to 7, then poured that water into the containter with the known volume measurements and recorded it volume. then proceed to mix the primer and allow it to shrink in the cup. After that week I removed the hardned primer from the mixing cup and placed it into that volume cup with water. I noted the difference in volumes of just the water and then when I added the hardned primer to the water.

I noticed the differences in the volumes from just mixed primer to week old primer and the old primer had a smaller volume. Now whether this was a great experiment method I dont know, just tried to use from what I could remember from chemisty class graemlins/sad.gif

But primer does shrink, when you leave it a containter you will notice it pulls away from the walls of the can. Also I noticed if dripped in small droplets the droplets will get somewhat smaller.

As for the dry spray on the K36 it would be a bad gun setup as the reducer will thin it out and it will spray nicer. When not reduced K36 does get somewhat dry looking. The only reason I use reducer with k36 is to extend the potlife, I prefer it without reducer but it sprays like crap come time for the 3 and 4th coat without reducer. But when reduced I dont get this problem but the film build is less then k36 without reducer. Its like a double sided sword I get my longer potlife but dont get the fill I want :(

the reason I like K38 better is because it fills better then 36. At the time I did my experiment I didnt have any 38 on me to see how much it shrunk as well

Hopefully I answered those questions...Eric

Yes you did, sir, thank you! smile.gif

Sounds like I should stick with the K38!
To add, if it has more solids content (for the higher build), it won't shrink as much (another plus!).

Crankshaft

I found a pic that I scammed from a chevelle club meeting. i did a demo on paint materials and such but theres a pic of some primer that I mixed up and allowed to shrink notice that it pulled away from the containter.
http://www.chevelles.com/showroom/bodyworkdemo111.jpg
Not the best pic showing what I mean to say but it works somewhat. You can see space inbetween the primer and where it once was higher up on the cup


Crankshaft yes the K38 is a high solid primer so it wont shrink as much as K36. The same reason body filler shrinks next to nothing as its a very high solid product. The reason I mention the primer shrinkage is because most people think its the filler when in fact its the primer shrinking...Eric

damn it

You know Eric, last night I was watching the Discovery channel with a "documentery" on West coast choppers and Jessie James. They showed a hand made fender that was going on a bike they were building. They needed to "Surface" the whole thing and spread a coat of RAGE gold on the whole thing!! I couldn't believe what I was seeing. This fender was not that bad, I mean I can't feel it, but it sure did not look anywhere near bad enough to need a 1/8" thick coat of RAGE!

All they needed to do was put a good application of Polyester Primer and it would have been a breeze. They are working WAY too hard, I'll tell you that.

On the polyester and etch primers issue. You know, I was told when I was a rep that it was simply the acids in the etch and the polyester resins "didn't get a long". I know it is not very technecal of an answer but that is what I remember being told. Now, if the filler if "fully cured" ( that's 12 hours by the book) it is no problem. Even though the DuPont tech sheet says not to do it, I have applied VariPrime over polyester filler many times without a problem. I know that S-W has a recommendation for over "fully cured" fillers and the two products are very similar so the "technologies" are going to be the same. I feel that DuPont is just CYA with it. They KNOW that if they say it is OK to do then guys will be spraying it over 1/2 hour old filler smile.gif .

The funny thing about the "resins just don't like the acid" thing is that PCL polyester primer recommends an etch primer while Evercoats polyester primer tech sheet specifically says NO etch primers :confused: