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How do you thin Bondo Lightweight body filler?

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Old 07-09-2003, 04:40 PM
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rsieminski
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Default How do you thin Bondo Lightweight body filler?

I'm going to use it as a leveler on a less than perfect plug for a mold I will eventually make. I have limted resources for these products, so Bondo is what I have to work with.

Can it be thinned with denatured alcohol, or acetone?

Can I mix less hardner to get a longer working time, like polyester resin?

Thanks,
--Rick
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Old 07-09-2003, 08:12 PM
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Default How do you thin Bondo Lightweight body filler?

Rick,

I think that the answers to your questions should be no and no. Because these filler products all tend to set so dang fast, there may not be enough time for the alchohol to evaporate properly. Mixing less hardener is not going to necessarily mean a slower set. It is more likely that you will get an incomplete cure - the kind of sticky mess that happens from time to time.

BUT is there anything wrong with trying it on some scrap first. It would pay to check cure, adhesion and workability.

Thinking about this on the run as it were, if the "repair" is a largish area but very thin, it might be better to "paint" multiple layers of epoxy resin rather than use a filler. It will take longer, might cost more but should give a far more durable finish.
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Old 07-09-2003, 09:55 PM
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Default How do you thin Bondo Lightweight body filler?

Polyester resin can be used to thin bondo, however by reducing the ratio of fillers to resin, it will increase the amount of shrinkage on cure. Try test batches first, too much resin can inhibit the cure and also make it difficult to sand in more than one respect....... I've mixed batches that were nothing but a sticky pile of goop.
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Old 07-09-2003, 09:59 PM
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rsieminski
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Default How do you thin Bondo Lightweight body filler?

Is there anything you can do if it wont go past that sticky phase?

I can adjust the cure time on polyester resin, by adding less MEKP, right?
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Old 07-10-2003, 12:53 AM
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Default How do you thin Bondo Lightweight body filler?

The best that I can suggest is to try small test samples. I've kicked bondo type fillers with MEKP, but it seems to work better with some brands than others, obviously dependant on the formulation. Just as with polyester laminating resin, the cure time of bondo can be adjusted with the amount of hardener used. Once it's catalyzed and has started to set there is little you can do if insufficient hardener was used. Time and small doses of heat can sometimes benefit.
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Old 07-25-2003, 09:59 PM
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Default How do you thin Bondo Lightweight body filler?

Don't even try to thin Bondo...Too much trouble. Just go down to the automotive paint store and get some 3M "Flowable" spot putty. You mix a hardener with it just like Bondo. The really cool feature of this stuff is that it cures without leaving that tacky top skin like Bondo and some other spot putties do.

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