Conflicting advice on the subject of buffing a car after wet sanding
07-23-2004, 12:54 AM
#1
Three Wheelin'
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Conflicting advice on the subject of buffing a car after wet sanding
As some of you may know, I recntly painted and wet sanded my 944. I personally screwed up the wet sanding process so bad, that I ended up having to spray a new Clear coat, and start the wet sanding process all over again. This time I started BLOCK wet sanding with 1500 grit. (Allways use a sanding block, or hard foam when wet sanding, I learned the hard way) I then moved to 2000 grit, then finally 3000. While preforming the job, I made sure to sand in the same direction the whole time, and kept the surface wet to promote sand paper longevity. After the sanding was complete I hit the car with some rubbing compound then polishing compound. The car came out great.
It seems as though everyone is on the same page, regarding the actual sanding process; however it seems that the buffing/polishing stage is still something not generally understood by all. I have herd countless people tell me not to use rubbing compound, I have also herd countless people tell me not to use polishing compund but to use rubbing compound. It seems kind of inherent to us, but buffing out a car is a true art, and I am reaching out to thoes who are good at this to give myself and others some pointers regarding the buffing/polishing stage of wet sanding a car.
TIA
Christian
It seems as though everyone is on the same page, regarding the actual sanding process; however it seems that the buffing/polishing stage is still something not generally understood by all. I have herd countless people tell me not to use rubbing compound, I have also herd countless people tell me not to use polishing compund but to use rubbing compound. It seems kind of inherent to us, but buffing out a car is a true art, and I am reaching out to thoes who are good at this to give myself and others some pointers regarding the buffing/polishing stage of wet sanding a car.
TIA
Christian
07-23-2004, 04:47 AM
#2
Race Director
Rubbing compound is roughly 1500-2000 grit and polishing compound is like 2000-3000. There's no "right" or "wrong" answer to your question. There's easily 10 different scenarios you can come up with starting with XYZ-grit sandpaper and ending up with a mirror gloss finish on your car. Here the general outline: 3M Detail Paint Finishing System
The specific procedure depends upon the type of equipment you have. A sanding block is of the utmost importance and for concours type of finishes, you want a 1/4-sheet aluminium block (actually a 10x2.5" 1/4"-thick rectangle). Sanding motion is not as important as evenness. If you rub each and every square-inch of paint the same number of times as every other, you'll be OK. Imagine sanding your entire car with a 1/4-sheet of sandpaper on an aluminium block by hand? Well, that's what it takes for the perfect finish.
When the rubbing compound comes in is whether you sand 2000-grit by hand or by machine. If you have a 1/4-sheet file-board pneumatic sander, then use the 2000-grit paper as it'll be much faster than by hand. But if you don't have a file-board sander, just a random-orbit polisher, then use the rubbing compound here. Even the term "rubbing compound" is way to generic as there's many types with different properties.
What you don't want to do is use a rubbing compound AFTER you've hit it with 2000 grit sandpaper because the rubbing compound is rougher than the paper, so you'll be taking a step backwards. Makes sense? It's not that rubbing compound itself is bad, it's just WHEN you use it is important.
Then the final step is the polishing. Traditional way is with polishing compounds. 3M makes some quick-buff polishing pads that you wouldn't believe. The first time I saw one in action, I was looking at a dull-sheen left by a 3000-grit sanding. Then this guy puts the pad on the buffing wheel and goes at it. I could've sworn there was some wax liquid he put on that pad and that's what was coating the paint and giving it the liquid gloss.. but noooo... it was the pad itself that was polishing the paint from a dull sanded finish to glossy polish in a single pass!!! Amazing!!!
The specific procedure depends upon the type of equipment you have. A sanding block is of the utmost importance and for concours type of finishes, you want a 1/4-sheet aluminium block (actually a 10x2.5" 1/4"-thick rectangle). Sanding motion is not as important as evenness. If you rub each and every square-inch of paint the same number of times as every other, you'll be OK. Imagine sanding your entire car with a 1/4-sheet of sandpaper on an aluminium block by hand? Well, that's what it takes for the perfect finish.
When the rubbing compound comes in is whether you sand 2000-grit by hand or by machine. If you have a 1/4-sheet file-board pneumatic sander, then use the 2000-grit paper as it'll be much faster than by hand. But if you don't have a file-board sander, just a random-orbit polisher, then use the rubbing compound here. Even the term "rubbing compound" is way to generic as there's many types with different properties.
What you don't want to do is use a rubbing compound AFTER you've hit it with 2000 grit sandpaper because the rubbing compound is rougher than the paper, so you'll be taking a step backwards. Makes sense? It's not that rubbing compound itself is bad, it's just WHEN you use it is important.
Then the final step is the polishing. Traditional way is with polishing compounds. 3M makes some quick-buff polishing pads that you wouldn't believe. The first time I saw one in action, I was looking at a dull-sheen left by a 3000-grit sanding. Then this guy puts the pad on the buffing wheel and goes at it. I could've sworn there was some wax liquid he put on that pad and that's what was coating the paint and giving it the liquid gloss.. but noooo... it was the pad itself that was polishing the paint from a dull sanded finish to glossy polish in a single pass!!! Amazing!!!
Last edited by Danno; 07-23-2004 at 05:15 AM.
07-23-2004, 05:05 AM
#3
Drifting
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Heh. Wetsanding sucks had to do my car 2 times. Wetsanded, sprayed it, clear coat, dry, wetsand, clear some more, wetsand and then buff. Its like a mirror and when you have around half a gallon of clear on your car it does look like a mirror even on dark paint lol. I just need to buff it again. When you wetsand after the first clear coat it lets the solvents out of the clear, hence the two times. My dad did most of it though( Helps that he painted for 25 years). Paint supplys only cost me 400$ lol. Dupont Chromabase.
07-23-2004, 12:32 PM
#4
Done With Sidepatch
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The AutoBodyStore.com Shop Talk is a great place for anything auto body related. A definite rennlist for autobody. The pros there are very helpful and they have an effective search function too.
