Painting question, color coat is too soft to sand |
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Painting question, color coat is too soft to sand |
Gudhjem |
Apr 4 2010, 12:21 AM
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#1
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Member Group: Members Posts: 133 Joined: 29-March 07 From: Castro Valley, CA Member No.: 7,629 Region Association: Northern California |
I've begun painting my car, panel-by-panel, starting with the trunk lid.
I'm using Interlux Bridghtsides paint. Yes, I'm rolling it on, mostly because I don't have a large compressor and because I am hoping to avoid all the mess of spraying in my garage. I spent a few days patching holes (luggage rack once upon a time I think), and spent a few days putting on a few coats of primer. Sanding the primer was no problem, and I've now started with the color. Problem is, when I try to sand the paint, it sticks to the paper. There's no dust created, the paper just gets clogged right away. It's as if the paint's not dry. The can says leave it at least 16 hours, I've left it 28, and it's not cold in California. Anyone know what's going on? (IMG:style_emoticons/default/confused24.gif) --Steve Here's before primer After Primer Sanding Block after trying to color sand |
realred914 |
Apr 4 2010, 11:10 AM
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#2
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Senior Member Group: Retired Members Posts: 1,086 Joined: 1-April 10 From: california Member No.: 11,541 Region Association: None |
cure time of teh primer is very important before you apply top coat, if you put some top coats on some uncured primers the top coat wont cure correctly. humidity and temp are also considerations. generally only laquers and catalized paints are wet sandable, most straight non-catalized enamels are not sandable (they dont get hard enough, at least for several months)
you MUST wet sand your paint, if you dry sand the paint builds up on the paper then teh paint is rubbing on paint, the paint stuck to the paper wont cut the paint on the panel, instead you get lots of friction and that makes heat the heat softens the paint and then you get more paint stuck to teh paper, and the situation gets worse. when you wet sand you should never ever have paint stuck on the paper. YOU MUST WET SAND!!!!! you MUST not press so hard as to not allow the water to wash away the residue. high sanding pressure can also soften the paint. sand lightly and sand WET. thickness of the paint might be a problem with curing. too thick and it may take weeks to fully harden. i suggest you try some test panels with different thickness and dilutions of paint, then wait different times before WET sanding and se what works. also remember the primer must be cured all the way, failure to let the primer cure al the way before top coat will result in top coat check marks as the primer shrinks months later. yes months later the check marks may appear if the primer was not fully cured before top coat, also top coat MUST be compatible with the primer. wrong choice and the top coat will soften the primer and cause problems with curing try to wet sand now and see if that helps that may be your only probelm. light pressure use a blcok (never your hand, the flat block will prevent finger marks from being sanded into the paint) |
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