"Robert11" wrote in message
...
Hello:

Have been playing for the first time with with BONDO to fill in some
siding cracks.

Boy, the stuff sure sets-up quickly; a matter of a few minutes.

Is there any way to lengthen the set-up time, without degrading any of
its other properties ?

Thanks,
Bob

The set-up time of bondo is controlled by two things - first, the amount of
hardner you use, and second, temperature. You can use VERY little hardner
in bondo and the product will still set-up fine. The hardner really isn't a
hardner at all. It is a catalyist which speeds the curing process. Less
catalyst = slower curing, not "won't cure". In fact, if you let bondo sit on
the shelf long enough, it'll cure without the hardner, and will have the
same properties as bondo mixed with hardner.

So, to answer your question, use far less than the recommended amount of
hardner and you'll slow the reaction. Also, the cure slows down if you mix
smaller batches, because the larger the batch is, the more it heats up. As
it heats up, it cures faster and creates a continuous cycle of getting
hotter and curing faster. It is an exothermic reaction, and can get out of
control to the point of catching fire. Spreading flaming bondo is best left
for the pro's ;-).