primers

[wombatgraphix]

an anyone tell the diff between self etching primer and sandable primer

[blinddog 99]

I can't, but I am curious myself. I just use catalyized primer, and sand as needed, guide coat and prime again as necessary...

[illfx]

THIS ONE i CAN HELP ON. Etch is usually ment for non-sanding, non-filling sealer. S E M makes a great self-etch spraybomb that i've used for years over everything(metel, plastics, crome, wood). and its not ment to sand. Just paint or fill prime after flash time(15 minutes or so). Does this help?

[Whit]

I've usually just use the surfacing laquer primer,, but
on occassions have used the etch as a sealer under it !!!
It tends to kill a bleeder underbase but if the surface
still needs prep,, as in dings, etc.,,, a surfacer is still
needed for a good glazing work surface !!!

[gphood]

an anyone tell the diff between self etching primer and sandable primer

Hi Wombat

Etch contains a chemical that bites into bare metal so the etch will stick to it. Standard primer doesn't contain that sort of chemical agent so it won't adhere properly. On the other hand, etch doesn't have enough thickness to sand back so it's main use it to bond your paintwork to the metal in the first place. Once it's flashed off you can go straight on with your sandable primer (also known as wet on wet), build it up with a few layers and then flat it back so you have a nice, even and keyed up surface that your basecoat and lacquer can go onto.

You can let your etch dry completely before going on with your standard primer but you should then scuff the surface to key it up for what's going on next.

The rule of thumb is to think "how is this stuff I'm spraying on going to stick to what's underneath it." If what you're spraying doesn't have a chemical in it to bond it to the surface then you need to key that surface with scotch pads or sanding paper.

Hope that helps anyway.

All the best

[Cowboy]

If I jump in. But etching primers, As some have said . are for dealing with bare metals, whether be it sheetmetal, aluminum, stainless steel, & in sone cases Plastics , Or resin type material.
Then is normally followed up with a non sanding epoxy primer, Read the directions as far as cure time & or the proper window. ( time before recoating ) with Your sandable primers ( or high build ) To build & Fill scratches or imperfections in the surface .
But all products must be compatable with each other & all curing times must be followed correctly. Also if dealing with bare metal, it must be cleaned properly with a metal prep, Then nuetralized ( because some preps contain acid, ) I use 50/50 water & white vineager.

Then reclean with laquer thinner, If there was rust present before then I would suggest using a rattle can product (called extend ) that nuetralizes the rust ( only on the effected areas ) then lightly sanding for bite with 400 grit, Then Use Your fillers, whether be bondo for deeper stuff . Polyester for less deep . Then, etch, epoxy, then, primer, & Of coarse for You ole timers thats using lead, You allready know . Sorry for butting in ,but If I can help I like to, Thanks for Your time. Cowboy,

[wombatgraphix]

cowboy thanks for butting in help is always great. thanks gp and all others that has help a lot now i have some idea what i am working with thanx again all for the advice

[gphood]

Thanks for the extra bits of info Cowboy. I really like how the gaps in my own knowledge are so quickly and easily filled on here. There are so many products out there on the market that it often needs places like this to advise when and how they should be used properly. I've picked up a lot of ways of doing things as and when I've been given jobs that require them rather than receiving proper training in a bodyshop environment so I'm finding all this information really helpful. I know some stuff, but nowhere near all of it. Between us we should be able to build these forums into a real mine of information.

[Ultra Al]

Good post Cowboy.
Some times after following Cowboy's procedure a sealer may also be used. i dont always use one but if Im working with something that my be apt to bleed I will. AL