Working with Bondo tips...

After many years of playing with ordinary epoxy and Elmers woodfill, I have graduated to Bondo :)
Any tips with how best to measure, mix, and handle the material. The can I bought comes with a measuring cup and talks about using a 1.5" bead per cup.
- Do you mix it all together in the provided cup or do you use something more disposable?
- How precise do you need to be in measuring out ratios of materials?
- Any tricks for applying and shaping the mixed material? (it seems to be very sticky)
- Any way to get a longer work time then 3-5 minutes?
Thanks for the advice
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blueman wrote:

I googled "bondo tips techniques" - first hit: http://tinyurl.com/7rfky
R
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RicodJour wrote:

That is good advice there.
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Interesting articl and thanks for the link, but: - It doesn't really answer any of my specific questions - It is targeted to body shop repair while I am interested in it more for *home* repair uses such as filling wood defects, etc.
I still have not found a good googled article addressing my questions specifically though I found more than I ever wanted to know about body shop techniques :)
Thanks
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blueman wrote:

http://tinyurl.com/d3c37 That's the search for "bondo tips techniques wood repairing". There's plenty of stuff in there about mixing and techniques.
The stuff isn't rocket science and you'll find your own preferred methods of work. I've heard everything from mixing it in a plastic bag to doing it on a piece of glass. The proportions aren't super critical. The hardener is a catalyst that causes the filler to harden. You can vary the properties of the final product by varying the ratio of the two components in your mixture. A greater proportion of hardener will make the bondo cure more quickly and be less flexible. Not enough hardener and it will never harden correctly.
Usually when you're mixing a two-part material with catalyst it's an exothermic reaction and the heat can be a problem as it speeds up the reaction. Some people refrigerate the components prior to mixing, but that makes it tougher to mix and won't buy you a lot of time. In that situation you should look for another product. Bondo has a lot of different products and several different hardners. You're not limited the the stuff you find at your local hardware store, nor to a particular manufacturer.
R
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writes:

is it a true catalyst? if so, it wouldn't be used up in the reaction, so would eventually cure the entire batch. bondo turns hard in the container, so one would assume that it would eventually, not "never", harden.
regards, charlie cave creek, az
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Charles Spitzer wrote:

The operative word, which you omitted in your reply, was correctly. It will never harden correctly. Never _is_ a long time, but as I've only been around for a relatively short time (measured in decades), I can't say for sure either way. ;)
R
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blueman wrote:

I just go to NAPA and buy the gallon can w/ the hardener/catalyst in a tube.

Almost absolutely imprecise -- more sets faster, less slower.

Slap it on and shape when it's set, just like body work. I have built molds and greased them to create shaped pieces or to fill in a missing area, for example.

Less catalyst.
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*then* 3-5 minutes? Then what?
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blueman wrote:

I like to make a puddle of the bondo and then make a smiley face on it with the hardener. That's about the right amount.

Go to an autobody supply store. The sell plastic mixing boards. They are easy to clean up with some lacquer thinner as long as you clean it up quick. Don't ever use cardboard to mix on since it absorbs some rein.

Not very. It just controls how fast it gets hard.

You need to sand with rough sand paper (40 or 80 is what I use) before you apply it so it will stick. Use the plastic spreaders and press down firmly so it fills in the cracks and crevices and sticks well. Try to get smooth coats so you don't have to sand a lot. But you can use a cheese grater to shape it once it firms up. If you find it too sticky and clogging your sandpaper then you didn't wait long enough for it to harden.

You can use less hardener but you still won't get a lot of useable working time. It's best to use several thin coats anyway.

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User Example wrote:

You can also chill the can down in the fridge and chill an old china plate to mix it on too. That'll slow down the curing of the unspread stuff.

Some random thoughts from my years of using Bondo to fix everything except a broken heart and the crack of dawn:
Exposed Bondo doesn't hold up very well to water exposure, so if it's going to be outside or splashed on frequently make sure to give it a good covering of paint.
If you are using Bondo to fill "holes" or gaps in wood, the adhesion is not very good. You can improve that a lot by driving in some screws or nails part way into the wood so their exposed shanks and heads will get surrounded by the Bondo.
If you need maximum strength, switch to the Bondo with the fiberglass filler in it. You can also imcrease strength by burying straight or shaped "reinforcing rods" made out of coat hanger wire. (Use the heavier style hangers.)
--
Jeffry Wisnia

(W1BSV + Brass Rat \'57 EE)
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blueman wrote:

I just use a scrap of cardboard. Cleaning up later is a waste of time... just throw it away when you're done.

Not very. Just remember the more hardener you add, the quicker it sets up. A little goes a loooong way.
--
Mortimer Schnerd, RN

snipped-for-privacy@carolina.rr.com.REMOVE
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On Mon, 12 Sep 2005 21:41:05 GMT, in alt.home.repair blueman

This is insofar as finish, not working time -- and I have always worked with external spackle, not Bondo, but the same may apply.
If you are doing a woodfill and it is fairly thick and dries slowly enough to form a not-tacky top "skin" and then cures through, and if you have a sample of the grained board are repairing then you can mash that into the spot and transfer a grain impression. I only work on my own house, but I did that several years back where i had two holes in the siding from a bird after insects (may have been indicative of another problem but nothing came of it) and after this little grain impression and the re-painting weathered in, i could not tell where I had made the repair.
FACE
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