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Sanding Basecoat w/ 2000 Grit Before Clear?

TWO

New Member
#1
My brother works for a company that makes various composite parts and then finishes them with a base/clear. In their instructions for laying the base/clear it specifically states and requires to sand the base with 2000 grit before applying the clear? He asked me why they would require this. I have no idea. I have shot base/clear for years in the custom restoration world and never have done this other then to remove minor imperfections, but I would always shoot another coat or two of base before clearing. I asked what base/clear products they are using and he is getting back to me with that info. They are non-pearl or flake bases, but has anyone heard of this requirement from a paint manufacturer? Has anybody tried this or see a reason to? Thanks!
 
#2
Most base brands say "do not sand" before clear.
If you have to sand then it needs more base sprayed before clear.
Most brands specify this in their tech. sheet.
 

TWO

New Member
#4
Sorry, I was not clear in my original post, the instructions from the company my brother currently works for that is manufacturing the parts, not the base/clear manufacturer requires that. The parts are for the aerospace industry. The part manufacturer (not base/clear manufacturer) claims they have always done it this way, for years. I thought it was very strange.
 
#5
A solid base won't be seriously affected by sanding, although I have seen it alter the color of the finished product slightly. To me, such a rule indicates that a crutch for poor techniques or conditions was implemented at some point.

A new wife who learned by observing her mom to always cut the ends off a ham before baking, finally asked her mom why that was. Mom answered, "Well, dear, of course it was because my oven was too small!"
 
#7
I don't think it does much one way or the other, unless the base is actually a 2K single stage, in which case sanding would be mandatory after a certain number of hours.
 
#8
doesnt clear peel off chromabase if you sand it? thought there was a big discussion about that awhile back. tech sheet says specifically not to sand the base.
 
#9
I forgot about that, Jim. Did some testing of my own back when I used S-W and found that it was apparently not susceptible, even though we thought it had a similar composition as the DuPont.
 
#10
doesnt clear peel off chromabase if you sand it? thought there was a big discussion about that awhile back. tech sheet says specifically not to sand the base.
Clear and any subsequent applied layer of base will peel off no matter what you do or how you clean it afterwards. I tested it 7ways to Sunday after I found that out and everything failed except when it was left alone and just cleared.
 

TWO

New Member
#11
Found out the base paint is Cromax. Tech sheet specifically states not to sand the base. I believe Crashtech was exactly right, poor paint technique was the culprit. He asked why this is done and they mentioned their original painter always did it that way and actually wrote the procedure. Of course, my brother sprayed it as the tech sheet recommended with excellent results. And he was saving time by not going through the extra step of sanding the base!
 

Chris_Hamilton

Trying to be the best me, I can be
#14
Cromax Mosaic can be sanded and recoated with itself before clear, Chromabase and Chromapremier should not be, though the TDS says you can nib dirt and recoat with itself before clear.
Have you used much Mosaic Crash? We switched jobbers and are now using Mosaic. Funky system but color match is good and it's pretty easy to spray.
 
#15
Have you used much Mosaic Crash? We switched jobbers and are now using Mosaic. Funky system but color match is good and it's pretty easy to spray.
Thank you for the recommendation! My jobber can get it, but I have been reluctant to switch away from Standox. It's getting expensive to use, though, since I also have ended up using their "Non_Stop" sealer for wet-on-wet applications, which is $300/3.5 liter and $275/2.5 liter activator. Color is between $150-180/ liter.