bondo question

[zed]

Since most body fillers absorb moisture, I've always wondered about how smart it is to wet-sand filler. Surely the water will be taken in by the filler, and be held against the bare metal - which is ideal rust conditions. Most of the old bondo repairs I have removed from my vehicles have signs of rust under the bondo. How to get around this? Dry sanding seems to give a rougher finish, and the paper loads up much quicker.

[Guest kamakazi620]

Since most body fillers absorb moisture, I've always wondered about how smart it is to wet-sand filler. Surely the water will be taken in by the filler, and be held against the bare metal - which is ideal rust conditions. Most of the old bondo repairs I have removed from my vehicles have signs of rust under the bondo. How to get around this? Dry sanding seems to give a rougher finish, and the paper loads up much quicker.

You "Wet Sand" base coat clear coat NOT the filler(bondo)

[Guest kamakazi620]

You "Wet Sand"base coat clear coat NOT the filler(bondo) or the primer

[INDY510]

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You wet sand primer.. and by then you shouldn't have too many bondo spots showing through the primer,, because it should already be FLAT

 

.... use a block sander with varying grit "dry" sandpaper .. . random orbit sanders are a joke for making bondo flat

[zed]

.

You wet sand primer..

I've read that primer is also not waterproof, because its made to hold onto the finish coats. My Haynes manual section on bodywork also says to wet sand body filler - strange

[72240z]

Body filler absorbing moister during finishing isnt that big of a deal so long a its fully dry before top coating. There are lots of schools of though on weather to wet sand filler or primer etc... The problem with its moisture absorption is over time, because its will deteriorate.

 

I personally only wet sand base and clear coats.

 

Also dont refer to fillers as bondo, its in insult to just about every other filler.

[edp]

use "no water" as a rule of thumb and you'll be fine. Dont wet sand filler or primer as another rule. Dry sand primer with a guide coat to find the hi & lo spots. Base coats are so thin a millage that sanding them is pointless even counterproductive as you want a surface for the cleat to "bite" into, the smoothness wont come from sanding base its in the primer/filler prep under the base then for the final smoothing / scratch removal you can cut & buff the clear coat.

[VintageRice]

Body filler absorbing moister during finishing isnt that big of a deal so long a its fully dry before top coating. There are lots of schools of though on weather to wet sand filler or primer etc... The problem with its moisture absorption is over time, because its will deteriorate.

 

I personally only wet sand base and clear coats.

 

Also dont refer to fillers as bondo, its in insult to just about every other filler.

 

X2 ! Bondo = dirty 5 letter word

 

Use Evercoat. Sand filler with 80 dry then 180 dry then 220 dry. Shoot high build primer, block with 220 again, spray one more coat of regular primer/sealer, then basecoat then clearcoat........THEN wetsand and polish (cut and buff)

[Z-train]

No point in wet sanding any filler/putty.Just don't do it like this: