|05-13-2008 09:22 PM|
Very well put Barry, thanks!
|05-13-2008 07:08 PM|
I did a class for about 50-60 painters in Mississippi a month ago and that question came up about primer shrinkage.
Perhaps exaggerated a little I said you can apply 20 coats of primer and not get any shrinkage, if each coat is allowed to flash properly and then cure out good before blocking.
OR you can get extreme shrinkage with just three coats if proper flashing and spraying technique is not followed. Perhaps a little exaggerated but pretty close to the truth.
Myself, I finish filler with 80 grit and all metal finishing is with a 24 grit grinder and if in a good mood will run over the metal finish spot with an 80 DA.
Just my way done for years and will not change something that works.
Primer over paint I always use 180 on the paint.
*With that said, you will have no issue with how you prepped the car if you follow the following.
*Spray first coat wet, never medium or dry--you want to fill the scratch and not take a chance of bridging the scratch.
*Let each coat totally flash before applying next coat and same with third coat.
As pointed out, production shops will sand primer in 30-60 minutes and paint but if its a car you want to look good and last let the primer set for a day or week before sanding.
Because you can sand a primer in thirty minutes does not mean the primer is totally cured.
Although not touted (out loud) primers range from full cure in a day (rare) to 18-22 days being more the norm in this industry.
Nano technology is changing this but in this industry very few primers are using it at this point because of cost but a couple of companies are.
|05-13-2008 02:09 PM|
Thanks to everybody, I get the message.
Cyclopsblown - Thanks, got it from an old commander in the Marine Corps, 8" Howitzers, had it posted above his desk in Vietnam, except his started with 'Artillery", he he.
|05-13-2008 10:57 AM|
|lets cut it up||All products shrink up ...some more than others. I don't recommend spraying paint over a car that has been just primed (same day in most instances) that way the solvents can get out of the primer and you wont have problems later. When I prime I wait one week before I block sand and re-prime or paint. Now I am not talking about a production shop doing fender benders though ...we have a whole different way of doing things in the repair world. I am talking about a high quality paint job that requires blocking and priming multiple times. JMO Tim|
|05-13-2008 08:26 AM|
|cyclopsblown34||I don't know diddly about PPG products...BUT, I really like your signature!!!!!!!!|
|05-10-2008 11:05 PM|
Well, glass smooth may be the wrong choice of words. All over the forum I see laying K-36 over 180 grit is acceptable, I'm way past that. Over the finish I end up with will be more DPLF then the K-36; I'll resand with 5 or 600 before base coat.
Thanks for the input, I'm open minded and appreciate it all.
|05-10-2008 08:44 PM|
First off, 220 isn't "glass smooth". Not even close! If you are going to use those high dollar paints, you might want to invest in some more sand paper. Also, if that guy says it won't shrink over time, I would let him paint it, as I would bet against him. I did not see where you said if you are painting in a paint booth or not, but most of the products now days are designed to be used in a paint booth, if you are doing collision work, where it is expected to be done fast.
|05-10-2008 05:50 PM|
After reading your post I was able to contact the PPG rep here in town. First, I think you misunderstood, I'm not covering 36 grit scratches! I've sanded this car to almost glass smooth with 80, 120, and final 220. I can't really detect any scratches, just my anal vision thing, lol. They recommended final sanding of the K-36 with 500-600 before base-coat.
I was told there is no issue with shrinkage for the PPG K-36 and that matter fact, current day paint products are designed to do a project, start to finish in a day, two maximum. Go figure...
Not to derail your experience or knowledge, just that a week sounded like a long time. Maybe if I were laying it on thick, I don't know. Thanks for the quick response, gotta love this place!
|05-10-2008 04:53 PM|
|speedydeedy||It will cover a lot but over time even the best products shrink a little.Do not try to cover 36 grit scratches. It will look good till it shrinks.Always sand it before primer sealer.And try to let it sit at least a week even if you are in a hurry to paint.|
|05-10-2008 04:27 PM|
What will K-36 Hide?
I've had DPLF primer on my car for about a year, when I shot it, it wasn't great, have some orange peel texture, not a lot, but visible. I've sanded with 80 grit, then 120 now 220. I can see what appear to be sanding scratches, but when I wet it, it looks pretty darn slick.
I'm going to shoot again with 2 coats of DPLF, then K-36, top and cc, PPG Deltron 2000 DBF base, 2021 Clear. I'm not 'anal' (my GF doesn't agree...), but how much will the K-36 cover?
I"ve searched the database and found different thoughts, but looking for more input about sanding or grey scotchbrite pad scuffing between primers and before topcoat. It won't be sitting, going to move right through to finish.