Getting lost with guide coat!

[Alex.]

Hello All

I have rubbed down my flaky paint areas and put on primer, then applied a thin guide coat of a darker colour to try to get a nice flat surface. But when I rub down (very gently, with 400 paper) I always break through the primer to the bare body. I've been round this circle three times, where am I going wrong?

TIA

Alex.

 

[pedrobedro]

That's what a guide coat is for, to show you the high and low spots. Where you rub through is high and where it stays on is low. 400 is a bit rougher than I use as well, more like 1000 well wetted. What colour is your top coat going to be?

 

[joe666]

you are not putting enough primer on if you are rubbing through all the time and try using 400 dry then 800 wet to finish it

 

[malcolm]

What paint are you using? Generally a guide coat is intended to be used after a couple of coats of filler (high build) primer.

 

[Alex.]

Thanks for all the pointers folks. Sounds like I've not been putting on enough primer and sanding too much! I'll try again.

I'm using an old spraycan for the guidecoat and the topcoat will be BMW 454 (very dark green)

Alex.

 

[Wayne.]

2 pack or celly primer ?? 1000 grade is to fine using this you will end up polishing the surface which inturn will lead to adhesion problems later on

 

[Alex.]

The primer is called Mipa Rapidfiller and it's not two pack, but I thought we couldn't buy cellulose these days??

I've had another go with a good layer of primer and rubbed down with 600 as I didn't have any 1000 in the garage. Worked fine, thanks to all for the tips, I now have a nice level surface to paint tomorrow if the forecast's right. So I hope 600 isn't too smooth!

 

[pedrobedro]

Never had any problems using 1000 to rub down primer. The last car I did was a Clio and we kept it 5 years, the paint was still on it when it went. I don't spend long on rubbing down, you can feel and hear when the roughness has gone off the surface. I never rub paintwork with dry paper, that's reserved for filler.

 

[Seano]

Ok, One mist coat, to get the surface sticky, then two double header coats of primer, let it dry, then a dark contrasting mist/guide coat, then making sure you use a rubbing block, block the whole surface down moving in straight back and forward motion using 6oo wetn'dry, the block will ensure that you rub down flat and even and not leave tramlines from your fingertips after rubbing in straight lines.

WcW

 

[joe666]

i rub all my primer down with p320 dry on a block then guide coat it and da it with p500 dry to remove the scratches, any bits that cant be sanded with the da get 800 wet sanded then if its silver im painting ill go over it wet with abralon 1000 on the da.
if you use 1000 first it will just run over the top of any imperfections you need some thing to cut into it or your wasting your time.
if you spot repair some thing your primer needs to be put on in stages first coat, gripper ie a very fine mist over the whole repaired area..
then work from the repair out ie
cover filler/bare area first no more,
next go a little bigger than the repair then keep doing this untill you have put enough primer on making sure you leave it 5/10 mins between coats to flash off you are aiming to get as much as possible on there so you have some thing to rub down.
never prime to a tape edge and leave straight lines on the panel as you will never get rid of the line and in trying to will rub through all over the place.

in your case Alex you need to be careful as the solvent will lift your paint edges as it creeps underneath so its important you get the primer dry in between coats use a hairdryer to warm it through this will make the solvents release faster.
Joe