Are the rolls of sticky backed sandpapers in fine grits better for block sanding than wet dry? It’s been a while since I have painted a car, kinda catching up with the changes in materials. I like the 180 longboard sticky paper for blocking areas of body work and I noticed the same sticky rolls of paper are available in finer grits. Is this a better way to go than the 400 wet dry?
After filler has been leveled to 80 grit,I like to block 150 dry on the PSA sandpaper roll.Courser grits will level ,finer grits remove the courser scratches.I usually prime bare metal with 3 coats epoxy then 150 grit then 3 coats urethane primer and 400 wet.
that's what I do too, long board with 80 and then block with 150 dry, then wet sand (no block) with 400. For wet sanding, tear the paper in half, stack them, and fold into thirds.
I have used the sticky back paper 150,220 and even 320 on a long board. (I believe I ordered from eastwood). Works great, also saves money if you have alot of sanding to do. For 400 to finer I like using the 3M wet & dry with water and a dense foam block. But you could write a book on the subject and everyone has different ideas. It really depends on what type of material you are working with.
DdoubleD above : I have used the sticky back paper 150,220 and even 320 on a long board. (I believe I ordered from eastwood). Works great, also saves money if you have alot of sanding to do. For 400 to finer I like using the 3M wet & dry with water and a dense foam block. But you could write a book on the subject and everyone has different ideas. It really depends on what type of material you are working with. this ^ 400 wet with foam block. Prime 800 wet with foam block Paint Sanding gets paint specific from there. Edit: darn I screwed up the quote.... again
The old variants of 2K type primers will clog anything, wet/dry, dry, any grit. The newer versions of urethane primers are worth breaking old habits. The old yellow "K 200" from PPG was perhaps the most punishing of surfacing primers. Then they came out with "K 36" to help that situation but it still wadded up finer grit papers. Today I've found that PPG 3055 "Velocity" primer is perhaps the best there is for speed, clean sanding, zero shrinkage, fast build and hold out (solvent penetration). Running a close 2nd, and maybe so affordable it's almost against the law, Shop-Line 202. About 1/3 the cost of "Velocity", nearly the same lack of shrinkage unless applied heavy, and like 3055 can be directly top coated if mil thickness is kept pretty low. I seal with reduced epoxy when using 202 for base color and reduced solvent penetration. Now that we know that, the sanding/blocking thing is up. If you're doing a multi-layered finish like base, mid (pearls and such), then clear you end up with a fairly heavy top coating. Heavy in both mil thickness and frankly weight as well. Sand too fine and it runs easy, spray lighter to avoid it, shitty surface and tons of cut/buff time. In such instances I like 3M "gold" 400 grit dry sanding paper. Yes, I said dry. Surprised? I admit I was too. The primers above "allow" a cleaner and easier process to surfacing. You can clean easily as you go, use way less paper because it doesn't clog, with a quick swipe of wax n grease remover it's easy to check your work. All the known best tools work well here too. Paint sticks, foam pads, etc., and of course not following edges and sanding in a large diagonal pattern which should be the golden rule when developing a surface. On many finishes you can see that finisher's sin, sanding along a body reveal which then leaves a trench dug into the finish near it the width of whatever tool was used. FWIW, I almost never use the classic red rubber "block" with the pins in it to hold the paper. Too hard, wastes paper, not good for much more than maybe a rough leveling of filler. I typically wet sand with 500 when I'm doing a single stage dark color. Since it's only 1 serving of top coat I don't feel the need for more of a mechanical bond. It's fine enough to create a nearly finish surface, and with only 3 standard and one reduced final coat I won't see even a trace of sand scratches once cured. With 500 wet it does make a bigger mess, requires a lot of cleaning before sealer and paint, not to mention the "mud" it creates on the shop floor. It's usually worth it for high end finish work but dry sanding is also a fine approach. What you're doing, where you're going with it, always up to the finisher.
I just blocked this '52 Willys with 180 DRY sticky backed paper and then followed it with 400 DRY sticky backed paper after the final primer...blocked it twice as well. Reason is I hate wet sanding...makes too big a mess in my garage...at least I can sweep up what's left on the floor... FWIW, I am not a pro body man nor do I profess to know more than a pro body man...I simply ask a lot of questions and hope my work comes out good... The car came out flat and the paint looks good. R-
thanks for all the information, I have old habits, still sanding the way I did when Lacquer primer was the standard. using 360 and 400 wd with blocks, pads and paint sticks. I picked up a roll of 180 psa paper from Napa today(they didnt have any 150) after work, it clogged much quicker than the 3m 180 gold sheets. so definitely some papers are better than others I like the idea of psa paper rolls especially in wet dry . I make my own sanding blocks some times and PSA paper rolls would make them much easier to work with. Nice work on the Willy's Studedude thanks for the detailed information Hilander, your the only the second person I have ever heard of that used solvent in the sanding process. My autobody teacher at Cuesta college in the 80's used to use prepsol with wetdry paper . He was a really interesting guy, in his 70's back then, told us stories about Henry Ford , which he had considered a personal friend.
I guess I should clarify something, and it's that I don't sand with it. Once I have something feeling good I clean that panel with wax n grease remover to create a gloss and provide a visual assist. You can do the same thing with water but it evaporates too fast for me and my nearly anal standards. I've heard a lot of things over 40+ years, even one, well decorum prevents description here, but he sanded with lemon oil. Yes, I said lemon oil (!), so imagine the situation of having to refinish. It was a lacquer job from the 80s and was literally "poisoned" by it requiring a strip and refinish as no repair could be performed. Like painting over motor oil
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