Evening all, Im doing a respray of a mini and im at the filler primer stage and guide coating that back but i keep sanding through even after my experience of doing a respray before where i sanded through i dont seem to have improved.

When i done a car last year i took a chance with some areas i had sanded through on and i had paint reactions where i have sanded back to the etch primer!
Now obviously i dont want this to happen again so i was wondering can i filler/primer then guide coat that, then if i have sanded through is there a primer i can put on that just literally needs smoothing off with out the need to go so mad flatting panels and to help seal the areas where i may have sanded through the filler/primer
Any help/ advice will be most welecome as i feel like im hitting my head against a brick wall right now what with prime sand prime sand lol Thanks Greg

If the primer is fairly even you should be able to get away with using a scotch pad to key the primer. Less chance of going through to bottom layers. With unstable paint layers I use a sealer to isolate and prevent reaction with new paint.

How much primer are you putting on? I am guessing cellulose too?

I used to use double coats of filler primer, 400 wet/dry, another double coat and so on, usually 3-4 double coats then a proper flatting with 600 grade or finer. I have never used a guide coat, but the principle is the same.

remember celly primers do sand back VERY fast (2K much better but a bit harder work, and the health issues etc)

so are you saying if i were to have used a isolator coat then if i did sand through i would not get paint reactions?

I basically found last time that the etch primer out of a can gave crazing like a spiders web, yes i have degreased and tack cloth wearing gloves i was extremely thorough

im actually using 2K but dont worry im taking all the precautions!! i have applied 3 coats so far but when i sand through im applying more primer but when i then sand again i end up sanding through surrounding areas obviously because i have sanded twice the amount on this area.

So im guessing theres no primer i can just put over the top as im only wanting to use maxmeyer filler primer to help aid getting the filler work as straight as possible

Thanks again guys

If you have use an isolator then if you sand thriugh you must put more isolator on.
But I still dont understand how you keep sanding though. Unless the shape is too far off to be dealt with by filler-primer?

You need an epoxy primer, don't bother with etch. You can fill over epoxy then rub back so you don't go through to bare metal, just google it and you'll get lots of hits.

Sounds like you are trying too hard to get it done quickly, you say you are using 2K, how many coats of primer did you put on and is it a high solids primer?

Are you hand blocking or using some sort of power assisted sanger, DA etc? power sanders remove paint very fast!!

There should be no need to use a guidecoat providing you take your time, if you are using a guidecoat and still blowing through then you are rushing.

I find it best to wet sand primer in a nice worm dry enviorment so the primer dosnt absorb any moisture. sand a tiny bit wipe off the water dont get it compleatly flat (matt) on the first pass, get the whole panel to almost flat then do another pass to take off the last bit. be espeshaly carefull on the edge of panels, this is were you will go through fastest.

hope this helps

tilly