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Old 03-11-2009, 07:09 PM
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Eliminate filler pinholes with dental pik and credit card

During what I had hoped was my final coat of primer on the sedan delivery, I discovered a rash of pinholes in one section of the roof area. Earlier on in the process I would have just applied some two part Glazecoat. But that would require a good deal of sanding and more importantly, another coat of primer (to prevent filler bleed through) AND another round of sanding to get it all smooth and straight again.

So I did a little experimenting just using some of the two part urethane primer I had been shooting. I have tried using primer to fill pinholes in the past but always had trouble applying it and completely filling the holes. The primer tended to just sit on the surface and not go to the bottom of the hole. When you sanded it later, the hole would just reappear.

So today I tried a couple of new approaches. Here's my "toolbox" for the experiment: A thin pointed brush, a measuring syringe, some dental piks and an expired credit card.



I cut a 5/16" strip off the credit card and trimmed off the ends just a bit to form a miniature bondo applicator.



I then mixed up a tiny batch of primer/hardener using the syringe to get the right ratio (this ended up not working too well so I eventually just used the 4 drips to one drip method). I then dipped the point of the dental pik in the paint to get a drop on it and inserted the tip of the pik into the pinhole. Interestingly, you can actually feel when the point goes down in the hole. The paint then wicks off the end of the Pik and into the bottom of the hole.



I then used the credit card applicator to smooth the paint on the surface. I found that it worked best to bend the card way over like this so a lot of flat surface dragged over the top of the paint. If you just use the edge of the card to scape the excess paint off, it tends to pull the paint right back out of the hole. For shallow holes, you do not even need to use the dental pik. Just dab some paint on the end of the credit card and apply to the hole(s) just like you would bondo. I let the primer dry two hours and then blocked it down with some 360 wrapped around a paint stick. The primer sands very quick and easy.



Here's a BEFORE shot of a section of pinholes...and then an AFTER shot of the same section. No more pinholes, no excessive sanding, and NO extra round of shooting primer and sanding down the entire area.





There are a few more shots of the process and a bit more into in my journal here. Oh, and I experimented a bit using the fine tipped brush to get paint down into the holes as well, but found it was a hit-and-miss deal. The dental piks worked much better.

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Old 03-11-2009, 08:46 PM
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Pretty cool, I had a smiliar situation with a divot in my clear coat on my deck lid. After it had cured I mixed up a small batch of clear and activator and with a toothpick I dabbed a little activated clear into the divot. After it had cured I block sanded it flat with 2000 then wet sanded the entire deck lid and buffed it. It was invisible in the shop, but in bright sunlight you could see a little ring. Well I left it feeling it wasn't that bad to re-clear the whole deck lid. That has been almost a year now and last weekend I was polishing my 34 and backed it out of the garage into the bright sunlight. I was putting my polish back in the trunk when I closed the deck lid and it hit me.....the spot was gone completely....couldn't see any of it.

Vince
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Old 03-11-2009, 08:51 PM
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cboy this will be very handy to know.thanks for sharing this. cole
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Old 03-11-2009, 09:34 PM
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Pinholes

I have had a couple (thousand) of these over the course of my body experience. I have used glaze with a little evercoat plastic honey mixed in to make it "semi self leveling". I then use a dulled razor blade as an applicator. then block with new 400 and going finer if needed. I would assume that you were not planning on repriming it, but I have never had any bleed issues that you speak of. (hope you didn't jinx me, I never even gave that a thought!) In the case where slight build or an edge appears I have been able to back drag it similar to a sag in clear. I have even done this over epoxy sealer! (dont ask how you block over, wipe over, tack over, and seal before you find it, but I have.... I like your idea, will try that to see how it works. Love your journal...
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Old 03-14-2009, 12:07 PM
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Man Dewey, your work amazes me. The more I see stuff like this the more I realize how rough my hot rod was.
I always thought that a rattle can was the answer to all my problems.
Great Work !!

454 RATTLER
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Old 03-14-2009, 12:44 PM
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Dewey, you know me and should know this isn't a kick your *** post.

You provided a great way to FIX the pin hole problem, however, one should never have to use it!

If the filler work is roughed into shape using a regular filler, then skim coated with a polyester putty such as Evercoats "Glaze coat" and fine tuned using the skim coat of polyester putty one will NEVER get a pin hole!

No kidding, this isn't a smart ars thing to say, please forgive me if it sounds that way but I NEVER get pin holes, EVER. Prior to primer there is NO pin holes, PERIOD.

It isn't a big deal, just apply a skim coat with a polyester primer using a reasonalble amount of pressure on the spreader and there will be NO pin holes to fix!

Fine tune your filler work, spread it with pressure to you are pressing out the air and pressing the filler INTO the previous holes and you won't have pin holes either. Without a doubt, to be it is the magic of using the "Emory Robinson" method. The mentor who taught it to me 30 years ago. I have literally called him up recently and thanked him for it!

I have used this method for all those 30 years and have taught it to many apprentices and even to a few journeyman who wern't too stuborn to listen.

Here is the second "Basics" I wrote a number of years ago.

Brian
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>



"Basics of Basics" Plastic filler ("Bondo")
By Brian Martin


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. And it is even in the Evercoat "MetalWerks" instructions. Mixing all "MetalWerks" products like RAGE and "Glaze Coat" (and many others) is recommended. I HIGHLY recommend Evercoat products! http://www.evercoat.com/

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.
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Old 03-14-2009, 07:06 PM
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Originally Posted by MARTINSR
Dewey, you know me and should know this isn't a kick your *** post.
Absolutely. You've helped me through a whole lot of painting jambs Brian, so I always appreciate your advice.

And I know exactly what you are saying. Under normal circumstances I do my filler work exactly as you prescribe. And as I noted in my OP, this only occurred in one specific section of the roof. And I think what happened is it was one of those fairly large low spots that I discovered well into the body straightening and I applied my normal Rage Gold, got in a hurry, and just sanded it and primered...rather than going over it with my Glazecoat. Can't say for certain because I don't remember, but I'm guessing that is what happened.

Bottom line...thanks again for the helpful commentary.
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Old 03-14-2009, 07:36 PM
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I'm not a professional bodyman by any stretch, but I did work as a painter in the aircraft industry for 9 years. Here's what I found.

Pinholes are either entrained air in the mix OR gas pockets formed from catalytic reactions with multiple components.

Since much of the paints/epoxies I worked with were catalytic cured or difficult to mix we had various levels of problems with pinholes in much of the product we sprayed.

I experimented with methods to reduce/eliminate pinholes using the following methods;

-Increased stand off time, works well for epoxy paints as this gives the reaction time to happen and lets entrained air/gas time to float out.

-Liquid mixing methods, You would be surprised how much extra air can be introduced into a mix by using various methods of mixing. For liquids it was determind by scientific method that centrifuge mixing was the superior method with the least possibility of entrainment.

-Solid mixing methods, It was determined that solids such as fillers and epoxy's needed to be "paletted" to remove the air entrained. In case you are not familiar with this method you use a flat "palette" to smash the mixture down into a thin layer and perform the mixing by rolling and thin layering, when the mixture was ready to apply the mix was scraped off the palette and then used once it had "kicked".

In short we found most of our problems were created by being in a rush to get the product mixed instead of taking the time to perform the mixing in a manner that introduced the least amount of air into the mix. The worst method by far was the short side bucket with the mixing stick used in a typical circular fashion the way every person uses to mix things in the kitchen.

As you can imagine in this industry pinholes mean rejects and rework, anything that can be done engineering wise to prevent reworking a panel or adding heavy fillers to an aircraft panel is scutinized very closely.

Next time you mix body filler try paletting the mix on a smooth surface and smashing the mix down into a thin layer to get the air out, if its paint try using a multi bladed mixer with a drill at low speed to centrifuge the air out, filtering into a clean container through a strainer will leave the air bubbles attached to the last containers wall surfaces...leave that small amount behind it is scrap.

Lastly it was found many painters did not give the product time to kick in the pot or they mixed the two part epoxy right before shooting after letting it sit which was unnecessary and only added air to the mix.

Like I said I am no expert but I have had some experience with shooting various products which are notorious for pinholes if not prepared correctly.
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Old 05-21-2009, 05:48 AM
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Those dental piks with the rubber tip are great for cleaning
the little holes in the spray gun's air cap.

this "whole" pin hole article should be in the "tip of the day" listings.
(I wish I knew what number we were up to.)
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