Fillers

fillers

bondo- while it is a generic term for body fillers, ie plastic epoxies
the actual product 'bondo'tends to have a higher solvent content
while this make it easer to spread, it leads to more shrink, as the solvent
evaporate and the product cures.
If you are going to use plastic fillers then buy a good quality ( we use evercoat rage,and then sparingly )
while body fillers have there place in auto resto, they are usally not used
correctly. If it is applied to thick it shrink and crack as it out gasses and cures.Thin coats of correctly mixed filler is the way ,curing then sanding between coats.
There are dif types( chem makeups) of plastic filler.
talc-
most fillers are talc based,talc being the main solid component
typically use by 90% of the industry for filling small areas and feathering repairs.
alm-
also called metal to metal filled, main solid is alm power typically used in areas of the car that have a higher vibration or shock loads
we use it primarily around doors/trunks and deck lids
kitty hair-
epoxy resin filler with short, fiberglass strands and talc for for its main solids og designed for fiberglass ,it is mostly used to pack it to bad repairs.(we see alot of this.) We use it... to make molds for shaping complex curves out of steel, or on fiber glass
out of those 3 kittyhair is the only one that is NOT hydroscopic .

lead-
to og filler, old skool, not much use today, we still do lead work for some clients, while it is a lost art, it is actually very simple to do.
non lead lead-
same as above but it is a tim based alloy with no lead in it
working temp is slightly lower than true lead
(thanks EPA)

the best way to do a repair, is to do it and not use ANY fillers and metal finish . this is unrealistic for most peeps , their check book, or skill level.
(most people do not have the patience to do this).
the final thickness on filler ( for our shop) can be no more than .075" (1/16"), I want it thiner than that

glazing putty-
talc based, but with much smaller particulate size than standard plastic filler. use primarily for pin holes, ( if you use good fillers correctly you wont have pin holes) and small repairs has a high solvent content -so it will shrink if used incorrectly .
NEVER use one part glazing compound EVER

I still HATE Bondo