reaction between high build & filler???

[fodtommo]

Hi All

Im hoping some of you bodyshop professionals can help.

I am currently filling they van prior to spraying - just over welds etc.

I bought a few rattle cans of high build - Hycote yellow stuff, just to check for imperfections and get it ready for 2 pack primer in the booth.

When you put just a little bit of filler on it to pick up those little nicks you only see once you put some paint on it appears to dissolve a bit??

The tin says suitable for celly and acrylic, but I would have thought all high builds should be suitable to skim over?

Any thoughts welcome?

Thanks

Tom

[jamesc76]

high build primer is just that, its the very final coat, you might get away with some stopper, or summit like dolphin glaze which is really fine filler? If it keeps reacting then its either a barrier cote or rub it all off!

[New Kentish Campers]

Ideally, you should try and remove the imperfections before you apply any primer. However, you can try using a fine filler, as James say's, or something like Plastic Padding PP100, which is a superfine filler. But only apply it using a very thin layer and then block it down with some fine paper, like free-cut or wet & dry, 320/400 grit & then re-prime once you are happy and satisfied that the base surface is good enough for paint.

As you are finding, good prep work is the hardest part of a repair, the actual final top coat spraying is the easy bit...

[SMartin]

The 2k filler is reacting with the 1k primer. Aerosol paints aren't very resistant to chemical reactions and the filler is just too much for it. You can maybe try 1k stopper (try 3M 1k red stopper), if what's being filled is very small (scratches or pinholes). You shouldn't really use standard fillers over paint coatings.

I'm not sure how you've gone about the process but if you're painting over bare metal/welds, you should really be using an etch primer after a good degrease. The final coat of paint will only adhere as well as its weakest layer so these areas are likely to be the first to fail. Be sure to degrease before applying filler to bare metal too.

In this order:
Metal substrate>standard filler>top stop filler>etch primer (on bare metal)>high build primer>top coats (direct gloss or clear over base)

Sorry if you're already aware of any of this :]

[fodtommo]

Thanks for all your help, id had a feeling that was happening - i just find it easier to see the blemishes with a guide coat of some sort.

[SMartin]

I quite like the powder guide coats but a can of matt black sprayed very lightly from a distance works just as well. Primer will probably not be fine enough to get into any small imperfections and won't be quite as easy to see