I am almost done blocking out my 2 heavy coats of slick-n-sand, and there are just a few areas that seems a bit low (not enough for filler though), and I plan on proceeding next to the high build urethane primer in the paint system Im going to be using (U-tech). I have blocked the Slick-n-sand with 120, because it cuts a bit faster, and clogs less than 180, and straightens better. Is there any need to sand to 180 or higher before laying on the high build primer?
If your going for more build primer and not going to your sealer and final paint, then no. I usually don't ever make it beyond 80 between coats of primer.
Yes, but not in this case. Moving up in the grit will cause the "bite" the new application of primer gets on the substrate to be less. So in this case it might actually hurt. Most build primers don't look for anything more than 80 or 120 on the substrate.
Cool, the sheet for the primer doesn't state what grits they expect it to be sprayed on top of. i just don't want to have any issues with shrinking into the sanding marks later down the line. I guide coated and blocked my bodyworked panels with 80, and then 120 before the slick-n-sand, so they were pretty straight before, so most likely, the few broader low spots are from my not laying down the slick-n-sand even enough.
120 is fine. I prime over 80 grit to 120 bodywork all the time with no shinkage. I feel 180 is to light for proper adhesion with primer. My .02.
Wow, I'm suprised at how many different opinions there area on this. When I am blocking a poly surfacer like slick-sand I start with 80 because it cuts fast and you can make it super straight. I then go back over it with 180 and remove all of the 80 grit scratches. I personally will never prime over anything coarser than 180 grit anymore. I have seen a lot of thing shrink over the years, and doing this for a living I can't have things shrinking on me down the road. I am not familiar with u-tech so I can't tell you how good or bad an idea it is to prime over 120. You'd think I was crazy after seeing my poly surfacer blocked and ready for regular primer, because after the 180 I block again with 320. I can guarentee you there will be no shrinkage doing it like that. And its crazy how nice you can make it. There is no problem with tooth for the primer to grip on to. You can safely prime over 320 with no problems. As it is done everyday in collision repair because you always feather out the surrounding paint in 320 before you prime. Anyway I'm not trying to write a novel here, bottom line is in my opinion, go over it agian with 180. I won't hurt anything and can only make it nicer.
Anything lower than 180 will show when the primer shrinks, all primers shrink over time and the finer you go the less it shows. I never use slick n sand, it does not hold up well over the years, I start with bare metal and prime with a high build dtm primer and block that with 180, grind the primer out of the low areas and fill, then re-prime and block with 180 and fill any remaining low spots lightly go over everything with 320 on a da with a soft pad, then final prime and block with 320 and wet sand with 600 then seal, base, clear, never any shrinkage problems
Hey Chad, A few suggestions on filler, blocking and sanding primer- I know after doing all the panel work on your Ford there is a big push to get it in primer, and into colour. Today, alot of guys are using high-build primers thinking they're saving time and thus, money. Ya gotta ask yourself though, what is the sence in you leaning on a product to do what should of been done with the filler. Doesn't most of that high-build primer wind up on the shop floor? Today's fillers are much more stable, and thus not lible to crack under expansion and contraction, unlike multi layers of the different primers and spot puttys trowled over the filler. I'd suggest you use a slime coat of your filler over a larger area than required to cover the damage/repair. Feather that coat of filler into ajoining areas of the panel/s, block with 80-180 and than afinal with 220. This leaves little if any need for high-build primers and puttys that will only bite you in the ass if given the chance. Never prime over old filler, primer or paint. Given the cost of today's paint materials, doing so is like takin' a piss into the wind and wonder- ing why you got wet. Leave the high-build and gee-wizz puttys to the guys in the collision business who are tryin' to beet the repair sheet! Swankey Devils C.C. "Meanwhile, back aboard The Tainted Pork"
Thanks a ton for the advice. I have really worked the body filler quite a bit, there are only a few very light lows. Im at the point, where Im going to guide coat the slick and sand (to be honest, I have sanded a LOT of the slick and sand off of the car) once more, but start with 80, then 120 or 180, and I really think that I can hit the car with another coat or 2 of 2k urethane primer (maybe reduced a bit so it goes on smoother), and then block that with 220, and have it straigt, and then proceed to 320-400-600 grits. That wont be layers upon layers of high build primer, and I think that should be a fairly stable base for my bb/cc.
This is the first negative view on slick n sand I have read. I know several people who use it, and have great, lasting results.
How many mils of primer are you going to end up with? Primer is not filler, use a good catylised spot repair putty for the lows instead of trying to cake the primer on. Too many mils will eventually fail, just my hard earned 2cents...
I dont know how to measure mills, quite honestly. I am using evercoat quantum glaze for fixing lows, but when I say one or 2 more coats of primer to get the few very low spots, they are just areas where the guide coat still shows, but dont really feel low when I run my hand across.
lots of helpful info here,,,it will come in handy for me soon,,,, chad,,your car rules,,,,, its gonna be stunning,,,you are taking the time to do it right, and that makes all the difference in the world..
Thanks! Soon? SOON? Hahaha, it took me well over a year to get from where you are now, to where I am, now block sanding. I guess Im just slow! Seriously though, no matter how boring all this sanding gets, its better than looking at a half built car, having to imagine what it will look like. Now the picture I had in my head is sitting right in front of me, all in one piece. This is where it gets fun!
Thanks. I am using the 3m dry guide coat, after starting with that a year or so for my filler work, I will never go back to fogging on paint as a guide coat.
And too few mills won't protect. So you need to find the happy medium. I don't think Chad is caking on the primer at all. He's skim coated most of the panels as far as I know and I think only has one round of primer on the car to begin with. I'm pretty sure he's in good shape.
The problem with slick n sand is the mil thickness, 2 coats is like 8 of 2k primer, you should be using a skim coat of body filler if it is in that rough of shape. Paints are not meant to be put on that thick and will crack and check over time, there has been many heavy primers like this that have come and gone over the years, all with the same reuslts. If attaining a quality paint job isn't a good enough reason not to use it then think of the health risks involved with using it, the catalyst used in it is a hardener for fiberglass resin. Even though no paint is safe to use this is probably the worst. Slick n sand is for people trying to cheat the process and make less work for themselves.
The Jalopy Journal
