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Technical Body Filler Basics

Discussion in 'The Hokey Ass Message Board' started by K13, Jan 11, 2020.

  1. Not rushing and don’t want to derail your train of thought here but wondering if you’re going to cover spray on fillers?

    And when you speak of putty is that referring to products such as USC “icing” ?
  2. Yes it's not a very big window.

    I can touch on them. Is there anything in particular you are looking for as far as info?

    Yes Icing is a putty.
  3. ken bogren
    Joined: Jul 6, 2010
    Posts: 701

    ken bogren

    Thanks for the great info.
    K13 likes this.
  4. Gofannon
    Joined: Feb 8, 2007
    Posts: 569


    Any tips on applying filler over epoxy etch primer?
  5. patterg2003
    Joined: Sep 21, 2014
    Posts: 604


    Thank you for a well laid out session on body fillers. The visuals of mixing will help a lot. It is tempting to add little extra hardener in when it is cold and then concerned that it kicked off too quick. I have been lucky so far but knowledge beats lucky any day. Thanks again for taking the time to put together this excellent thread.
    K13 likes this.
  6. blowby
    Joined: Dec 27, 2012
    Posts: 6,744

    from Nicasio Ca

    In my auto body class they have special clip boards with heavy paper to mix on and apply from. When done you just rip the sheet off and go to the next one. Fist time I have used that, industry standard? The spreaders go in a mixing cup with thinner and a scouring pad.
  7. Well since it seems that spreader marks in my final skim coats are my nemesis, so I’ve been leaning on the spray fillers. Project gets to primer stage quicker “for me” with better results. And then it gets out of primer and into paint stage quicker too. Mostly it’s the less sanding labor I find so attractive.

    So I guess touch on the pros and cons.
    What to watch out for and some what not to do info as well.

    Several guys I know have mentioned cutting their filler with icing,,,mixing the two. A smoother creamier easy to spread and sand for tight coats. Any problems with doing that?
    osage orange likes this.
  8. Almost didn't read this... And come to find out, its required reading! Thanks for sharing your knowledge.
    osage orange and K13 like this.
  9. bchctybob
    Joined: Sep 18, 2011
    Posts: 2,304


    Thank you, thank you, thank you! Now I can get started on my roadster and at least have a fighting chance to get it right. I am going to wait until the temperature I gets back up. I think I can find other things to do.

    Sent from my iPhone using The H.A.M.B. mobile app
    K13 likes this.
  10. 57Custom300
    Joined: Aug 21, 2009
    Posts: 1,302

    from Arizona

    Thank you for the info. I can fix anything mechanical but I'm just plain dangerous with body filler in my hands.
    32SEDAN and K13 like this.
  11. alchemy
    Joined: Sep 27, 2002
    Posts: 15,698


    Now we need part two: Sanding Body Filler - The Tips and Tricks of the Pros
  12. I assume you are meaning an epoxy primer and not an etch primer. I would not recommend putting fillers and putties over an etch primer there are too many variables with the acid in etch primers that can lead to massive failures and it can take a while for them to appear.
    Polyester and Epoxy are a different animal and you have to be careful because in general they don't like each other but you can put polyesters over some epoxies.. This is where Technical Data Sheets are imperative to read. First you need to make sure the primer manufacturer says polyesters are compatible with their epoxy. Some are, some are not. Second you need to know the full cure time/temperature of the epoxy and you have to let it sit for that full cure time. Once you have established it can be done and you have left the epoxy long enough you approach it like any other repair. Rough the surface with sand paper blow off/ wipe with fast cure solvent and apply.

    I wouldn't call them an industry standard but there are a lot of shops that use them. I love them for demos and working at home. Way easier than cleaning a board. The paper on these boards is coated so that it doesn't absorb much. That is what I used for the pictures in the mixing section. Just a really big one.

    As long as you are not abusing the product (putting too much on) there is nothing wrong with the way you are doing it. The danger with high build poly primers is when they get too thick they have a tendency to get brittle and crack like body fillers will. As long as you follow the manufacturers guidelines for film build you are fine. Follow the flash time recommendations and if you are putting heavy coats on extend the flash times to the upper limits to ensure all the solvents have time to make their way out of the product before reapplying. And, of course, just like fillers they need to be properly catalyzed or the same issues that occur with fillers will occur with them. Shrinking if under catalyzed and being even more brittle if over catalyzed. The only real con is the time it take the primer to fully cure compared to a filler or putty but if you are not a production shop trying to churn things out that's not a big deal.

    Not sure when you read the first sections but I went back and added a bit about thinning product that had slipped my mind when I first did it. Generally it is fine to mix thinner products with thicker to adjust consistency. Best to keep the products in the same family of manufacturers and if a manufacturer has different types of fillers (different resin technology in different lines)you should keep like products together.
  13. 6-bangertim
    Joined: Oct 3, 2011
    Posts: 382

    from California

    THANKS so much for shedding light on fillers! Now, can you sugest some products that are more 'user friendly' for us troops in the hobby? I have ZILCH experience with fillers and putties, and Eastwood's catalog is overwelming. On the other hand, every parts store has Bondo on the shelf... What materials would you suggest for a total noob?
  14. duncan
    Joined: Aug 23, 2006
    Posts: 1,127


    Thanks, great tech. What is the shelf life of spay poly (such as Slick Sand) hardeners.
  15. Thanks
    The cure time is ok with me, I got other stuff to do while it sits. That other stuff getting done is much more productive than me chasing spreader marks with fast cure putty.

    I’ve been playing with getting the poly primer to reduce the texture without much luck. There’s quite a bit of product that’s busy building a texture so that leaves considerable sanding and product on the floor before developing a surface.
    Any tricks to help reduce the texture? I use a
    2.2 tip and I’ve played with the air pressure travel speed, flow rates.
  16. Without getting into specific products I would say try and get the highest quality product you feel you can afford. In general they will be the easiest to work with in all aspects. Sandability, spreadabilty and self leveling characteristics are the factors that dictate how "easy" a product is to use and top of the line products will give the best of all three of these. Lesser quality products will be a compromise in one or more of these factors making them harder to use. As I mentioned above some of these can be manipulated by manufacturers (they all do it)to improve certain aspects and keep cost down (it's usually sandability as that's what most fillers are primarily judged on) but the cheaper products will fall down in other areas that make using the products easier. I will see if I can pick up some cheap filler and show some of the differences. I am talking about this week.

    MEKP style hardeners degrade faster than BPO style and a extremely susceptible to UV degradation so first and foremost keep them out of of direct UV light exposure and then they are generally good for a year.

    Unfortunately texture seems to be inversely proportionate to film build with poly's. There are thinner poly's available that will lay down very smooth but you get way less film build out of them.
  17. john worden
    Joined: Nov 14, 2007
    Posts: 1,610

    john worden
    from iowa

    Thanks for this info.
    I mix filler on a small piece of clear flat laminated glass. It's easy to keep clean with razor blades new or used or thinner.
    You can also draw a 2" and a 4" circle on the bottom side that show through and act as guides for filler/hardener amounts.
    charleyw, 4woody, K13 and 2 others like this.
  18. 51pontiac
    Joined: Jun 12, 2009
    Posts: 136

    from Alberta

    Thank you for a very readable and easy to understand write-up! I know this will be a huge benefit for me over the next few years. Amazed now that the stuff I did 30 years ago turned out ok (well, slightly better than mediocre) because I really did not have a clue what I was doing.
    K13 likes this.
  19. Dino 64
    Joined: Jul 13, 2012
    Posts: 1,854

    Dino 64
    from Virginia

    Thanks for the info, very helpful. One question, while working on a panel, I noticed I got a streak of activator in the filler. Unfortunately I didn’t see it until it was on the panel. Should I sand off that area and re apply more filler ?
    K13 likes this.
  20. What probably happened was you had a bit of unmixed hardener on your spreader when you were applying and it streaked across the top of the filler on one pass. It is probably just right on the surface and should be removed to avoid any chance of it bleeding through your primer and staining you finished paint. If it's only the one spot you don't need to remove all the filler in that area just the hardener streak.
    Dino 64 likes this.
  21. Glass would be a great mixing palette as it will absorb nothing. My problem is I would be replacing it ever 2 days because I broke it.:oops:
    Dino 64 likes this.
  22. Dino 64
    Joined: Jul 13, 2012
    Posts: 1,854

    Dino 64
    from Virginia

    Thanks @K13, I use those disposable paper sheets as well, I have noticed some of the activator is absorbed by the paper. It’s an Evercoat product, wonder if that’s a problem. I was using a piece of plexiglass to mix on with a 4” circle on it before I got the paper
  23. They are fine. The dyes in BPO hardener will stain pretty much anything. Those sheets have a coating on them to keep them from absorbing too much. It's the reason the tear away sheets work as the product doesn't soak through the paper to the next sheet.
    Dino 64 likes this.
  24. 57JoeFoMoPar
    Joined: Sep 14, 2004
    Posts: 4,598


    This is an awesome thread. Thanks for the great info.
    K13 likes this.
  25. My buddy refuses to use anything but scrap cardboard for mixing mud. I tell him, I tell him again.
    K13 likes this.
  26. goldmountain
    Joined: Jun 12, 2016
    Posts: 1,977


    It is -28 C outside today and not much warmer in the garage with the heat off (I'm both cheap and poor). Good excuse to put off doing the dreaded body work part of this build.
    K13 likes this.
  27. It has been a miserable week. :(
  28. Ford blue blood
    Joined: Jan 4, 2009
    Posts: 635

    Ford blue blood

    Fantastic info. I can say K13 is 100% correct with using the best you can afford! My paint guy is very good, knows his products very well, shares the good and bad of each item he stocks and has steered me to the top of the line filler and icing. Best move I ever made! Being a hobbyist learning is my biggest helper, the price difference between the top of the line and mid range is not great enough to worry over given the immense increase in finish quality!
  29. alchemy
    Joined: Sep 27, 2002
    Posts: 15,698


    So, spill guys! Which product do you think is best?
    sleepchamber and Dino 64 like this.
  30. earlymopar
    Joined: Feb 26, 2007
    Posts: 1,206


    What filler product/s do you recommend for parts that get hot such as an oil pan?

    - EM

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