Have Autobody Questions ? - Topic

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Mar 9 2016 08:06pm

Quote (Thomadinn @ Mar 9 2016 08:31pm)

I'll bite. For you or Andy

I'm using a cheap bondo I got from ace but can't seem to mix it properly to avoid very minuscule air bubble that still appear after primer. Any recommended, maybe tube squeeze/pre mixed stuff to fill these small air pockets in? I'm talking tiny hole less than 1mm in size

Those are called pinholes. You're going to want to mix the filler in a folding motion instead of a stirring motion. (10:1 ratio unless otherwise stated on filler) This will eliminate most air bubbles but you will still have some pinholes more than likely. If you have the extra money for the project buy a finish coat filler. I recommend Icing. This is a much more thin filler and you're only going to want to mix as much as you absolutly have to. This isn't for filling large areas this is simply made for eliminating pinholes and minor gouges and sanding scratches. Use a thin layer. If you can see your light weight (the bondo for the heavier damage) through the Icing almost like you're looking through a cloud- you've just done what you were supposed to do perfectly. (Of course this doesn't account for areas that need more filler or less filler like high and low spots. Those will either look darker or lighter. Always remember to make sure you have good physical bond to the surface so sand it first but make sure you don't over sand and ruin the filler work you've already done. Also use a tack-rag or blow off the surface to remove any dust. If you don't want to use Icing or have the option I suggest priming them out. Use either a heavy primer or a light primer but heat will be your friend here. Lightly cover area while drying with heat gun quickly. Keep dusting. Gradually increase coat wetness until pinholes are filled. Pinholes can be a big problem in a finished product. I hope this helps and I didn't TLDR it. Be careful with the heat gun by the way.

F150

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#12

Mar 10 2016 08:03am

Quote (Thomadinn @ 9 Mar 2016 21:31)

you got to mix it a certain way to remove air bubbles ._.

OldAndyAndTheSea

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#13

Mar 10 2016 08:31am

Good info thus far.

More food for thought.

How you mix the material does make a difference, as explained above... But it does not completely eliminate air, as flipping it does still gulp - just not as much as swirl mixing.

That said, the thickness of the material applied can also play a large role in this. The inevitable trapped air in the polyester filler needs to off-gas as the material cures, if you are using Bondo (inappropriately) to fill large gaps, and are mixing in large batches this could lead to pin holes.

Temperature/proper mixing ratio can not be stressed enough either.

Top coating with a nice epoxy primer sealer can also help greatly to eliminate/fill pin holes, once they are established.

Luckily, there are a bunch of different ways to do it, it's up to you to decide which is most feasible for your project.

TheBroodwich

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#14

Mar 10 2016 09:35am

Quote (Dragon_MMA @ Mar 9 2016 05:11pm)

No idea who this is. First post in Auto SF.

Yes, buy make sure you have a lot of coarse sand and gravel in the mix or else it won't come out as well after buffing.

Lol.

Thank

And Andy is the man, check his progress thread on the datsun "been shaving my manifold" one of the coolest threads here imo

Sancti

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#15

Mar 10 2016 10:23am

Quote (OldAndyAndTheSea @ Mar 10 2016 09:31am)

Quote (TheBroodwich @ Mar 10 2016 10:35am)

Thank

And Andy is the man, check his progress thread on the datsun "been shaving my manifold" one of the coolest threads here imo

Going to look right now.

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