Sanding primer

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PostPosted: Mon Jul 15, 2019 3:29 pm
I'm so sick of sanding primer...

How do you sand your primer from start to base?

After primer i been sanding with 600 to get it flat then 800. It works ok but takes forever. Everytime i go corser or DA i get burn throughs.



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PostPosted: Mon Jul 15, 2019 4:26 pm
Sanding is a BIG part of the Game when Painting cars! It makes or breaks a great paint job! I often say if dont like sanding Painting cars aint for you!
Sanding separates disasters from Fantastic jobs

That said there is a Sticky in Blue at the Top of the page you should read them starting with this one viewtopic.php?f=5&t=17445 I am sure it will help a lot! and you will find your answers there.
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PostPosted: Mon Jul 15, 2019 5:15 pm
check out the sticky, also what kind of primer are you using that known then someone can probably help.
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PostPosted: Tue Jul 16, 2019 3:28 pm
Dokus wrote:I'm so sick of sanding primer...

How do you sand your primer from start to base?

After primer i been sanding with 600 to get it flat then 800. It works ok but takes forever. Everytime i go corser or DA i get burn throughs.


You may get it smooth with 600 but you won't get it straight if you're
going over a non straight surface, like bodywork.

600 should be your last sanding before paint, 600 is plenty fine enough to have
paint fill the scratches.

If you're trying to get it straight, sand with 150 to 180 first. Even with a soft block,
long strokes with those coarse grits will straighten it fast.
JC.

(It's not custom painting-it's custom sanding)



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PostPosted: Thu Jul 18, 2019 8:15 pm
Any trade you do has uncomfortable tasks to do. Sanding is a major part of a lot of different trades.

The professionals would know better but I've never sanded primer with anything finer than 400. I've never had sanding marks show through the paint.



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PostPosted: Sat Jul 20, 2019 3:33 am
Thanks for all the respons. Its not so much that i dont like sanding but its feels like im doing it wrong which result in unnecessary long sading.

The products im using is Mipa 2k acrylic filler and Standox Standohyd base.

The parts i justed finished painted have been painted before but i had some clear dryspots so i decided to redo them. Since they were already straight i just sanded everything flat with p500. 2-3 coats of primer, sanded with p600 and then p800. Almost everytime i get burntrough having to reprimer. Since i dont have any heating system i have to wait everytime i have to reprime.

The reason i been using finer grits is because i have problem with scratches showing trough the base. According to the Standox Standohyd tech sheet you should spray 1 full coat + 1 effect coat. I never get it to work. The paint looks good but there is allways some 800 scrathes showing trough. If i paint "normal" with 3 coats its fine, no scratches but thats not what the data sheet is saying.

Datasheet can be found here:

http://sdstds.sxcolor.info/#Tds/US/EN/Search

Use 801 standohyd

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PostPosted: Sat Jul 20, 2019 7:45 am
I'll just throw this out there with your last comments.... a "coat" of any substance is up to interpretation by the person applying it and the final mix/reduction of that liquid. I was a wood and finish instructor for about 19 years when I was younger. I taught many adult professional people and did a lot of spray demos. We ran the range of guys "hammering" on coats to some just literally "wisping" on materials. Manufacturing spec.s about "coats" are based on wet film (mil recommendations) application that dries and gets you to the final dry film. In simple terms.... my 2 or 3 coats may hide/fill in a lot more than your 2 or 3 coats..... I have never had 800 scratches show up in my base.
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PostPosted: Sat Jul 20, 2019 9:16 am
Using guide coat on your final wet sanding will ensure you have eliminated scratches.
P600 gives a good surface for solid or metallic paints.
I ALWAYS spray at least 3 coats of base and sometimes more if using a lighter color. Nothing more frustrating than having gone through all this work to realize you didn't get full coverage or see blotches, stripes, etc.
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PostPosted: Sat Jul 20, 2019 5:40 pm
DarrelK wrote:I'll just throw this out there with your last comments.... a "coat" of any substance is up to interpretation by the person applying it and the final mix/reduction of that liquid. I was a wood and finish instructor for about 19 years when I was younger. I taught many adult professional people and did a lot of spray demos. We ran the range of guys "hammering" on coats to some just literally "wisping" on materials. Manufacturing spec.s about "coats" are based on wet film (mil recommendations) application that dries and gets you to the final dry film. In simple terms.... my 2 or 3 coats may hide/fill in a lot more than your 2 or 3 coats..... I have never had 800 scratches show up in my base.


But how do i know i get the rigth tickness? I always use a viscosity cup then set up my gun so its wet so i get the cigarr witout run, then spray on thick and slow. Fishined primer is smothed when you feel with the hand. When i sand its is course not flat, maybe i start with to fine of a grit and work the areas to long? Its not every scratches showing, more random scrathes from the x pattern.

3 coats works but what bugs be is tbe data sheet says 1 full + effect which would be nice since it uses less paint and this paint is more expensive of that reason. Just finshied two pieces of cladding with good result. 3 coats + effect

Edit: i use guide coat. It doesn't show anything. This time i sprayec dark blue, same problem with light blue, all metallic. Never had this problem with soild black.



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PostPosted: Sat Jul 20, 2019 8:26 pm
Primer is inherently thick. If you are not getting enough thickness it sounds like you are over thinning the primer.
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