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Author Topic: What does Rubbing Compound actually do?  (Read 9835 times)

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javeryh

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What does Rubbing Compound actually do?
« on: June 03, 2007, 11:01:19 pm »
OK, as some of you may know, I'm in the process of putting a pink automotive/piano finish on my cabinet.  What a pain.  Anyway, I just finished (I think) wetsanding 1/2 of my cabinet which had 2 coats of primer (rolled), 6 coats of paint (rolled) and 25 coats of lacquer (sprayed) on there.

I spent 5 hours on the thing using 1500 grit sandpaper but I can still see a bunch of reflective sparkles all over the place when the light hits it just right - these are small divots that are still present even though I've sanded like crazy.  I don't know what to do next - I'm debating whether or not to continue sanding this week trying to remove the tiny divots or if I should move on to the rubbing compound and polish.  Will the rubbing compound remove those divots?  I'm not so sure the rubbing compound does anything to be honest - I applied a bit to a lint-free rag and started rubbing it in and I didn't notice a difference at all with the finish.  The divots were still there. I was rubbing in a circular motion until it was completely dry.

Also, due to the sanding there are some sections that are starting to appear duller than others - I'm not sure if the dull sections indicate that I am getting the finish I want (and I just have to keep sanding) or if they indicate that I've completely sanded through the lacquer and I'm sanding the pink paint.  The last thing I want to do is sand through the paint to the white primer or worse, the MDF.  I am quite frustrated.

Any tips?  Anyone know what I'm talking about?  Am I insane?

TOK

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Re: What does Rubbing Compound actually do?
« Reply #1 on: June 04, 2007, 06:46:42 am »
Rubbing compound is a super fine abrasive. If you can feel it with your finger, rubbing compound isn't going to do anything. Sounds like you might be at the middle of the wet sanding stage.

I don't think you're insane, but I never understood trying to obtain a show car finish on machines that were slapped together in 20 minutes in a factory. Its just not how they were.
« Last Edit: June 04, 2007, 06:49:43 am by TOK »

javeryh

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Re: What does Rubbing Compound actually do?
« Reply #2 on: June 04, 2007, 10:11:15 am »
Rubbing compound is a super fine abrasive. If you can feel it with your finger, rubbing compound isn't going to do anything. Sounds like you might be at the middle of the wet sanding stage.

I don't think you're insane, but I never understood trying to obtain a show car finish on machines that were slapped together in 20 minutes in a factory. Its just not how they were.

You are right - I am in the middle of the wetsanding stage.  ;D 

So if the surface feels smooth to the touch then rubbing compound isn't going to make it any smoother?  What about the polish/wax?  I guess I'm going to go through the motions and apply a few coats of each but I was expecting to be able to notice a difference visually...

Also, the reason I want to achieve a show car finish is because this thing is going in my daughter's room and everything in there has to be fit for a princess!  The cab I'm building doesn't look anything like any "real" arcade cab other than the shape.  I want it to be a one-of-a-kind piece of furniture that only she has.  If I were building a replica or even a full sized one for myself, I probably wouldn't apply this type of finish... we shall see in a few months though when I start on cabinet #3!   :cheers:

patrickl

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Re: What does Rubbing Compound actually do?
« Reply #3 on: June 04, 2007, 10:52:23 am »
Rubbing compound is supposed to take out the fine swirls that are left behind after wet sanding (make dull surfaces shine). It's not going to get rid of divots or scratches that you can feel.

If you are still having divots then maybe there was too much orange peel in the paint job before you started sanding? Maybe another layer of lacquer and then sanding again? You should be careful not to sand through the lacquer otherwise you mess up the paint underneath.

I just bought myself a new car and I was surprised how bad the paint job on those cars looks these days. On my current (old) car the paint is really quite smooth and shiny, but on the new cars that I saw they are not smooth at all. Lot's of orange peel or at least a non flat surface. OK they cost half of what my old car cost, but still.
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ScottS

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Re: What does Rubbing Compound actually do?
« Reply #4 on: June 04, 2007, 11:18:39 am »
Perhaps you've moved up to the finer grits of sandpaper too quickly? As an extreme example, lets say you sanded with 40 grit paper and then moved directly to 2000 grit skipping everything in between. You can sand for as long as you want with the 2000 and you're still going to have huge imperfections left over from the 40 grit paper. Ideally, you'd use every grit between 40 and 2000 in order to obtain the smoothest finish possible in the least amount of time. Skipping grits can work, but I generally find it requires more time.

If you're sanding with 1500 grit and the surface isn't already glass smooth with no visible imperfections, then I'd say you probably didn't sand long enough with one of the coarser grits. The only solution may be to go back to a coarser grit, sand away the divots, then proceed back through the finer grits. Then move on to rubbing compound and polish.

If you don't already have one, get a light you can shine across the surface you're sanding at a very low angle. This really helps you see the scratches in the surface left by sanding, which will let you determine when you can proceed from one grit to the next.

SavannahLion

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Re: What does Rubbing Compound actually do?
« Reply #5 on: June 04, 2007, 03:46:50 pm »
I just bought myself a new car and I was surprised how bad the paint job on those cars looks these days. On my current (old) car the paint is really quite smooth and shiny, but on the new cars that I saw they are not smooth at all. Lot's of orange peel or at least a non flat surface. OK they cost half of what my old car cost, but still.

I have the same orange peel look across the lower 1/4 of my Tacoma. I asked a car buff about it and it's not the paint that does that, it's what's underneath it.

Automotive paint, by its nature, is very porous. So if you get standing water on it for any length of time, the car body will rust. That's partly why you have to wax your car, it seals the porous paint and prevents rust. Most people, however, don't wax their car... ever. So car manufacturers actually add a layer of of some kind of rust inhibitor (he used specific phrase, but I can't remember what he said) especially around near the bottom where water and wet mud tend to collect and stay. The anti-rust coating is really thick, a bit like tar I guess, and it blotches on in an orange peel appearance. Either the car manufacturers are too cheap or are unable to sand the orange peel smooth before applying the actual paint layers.

You can remove the paint/anti-rust and repaint to get rid of the orange peel, but then you loose any rust protection and have to take care to wax the car on a regular schedule.

patrickl

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Re: What does Rubbing Compound actually do?
« Reply #6 on: June 04, 2007, 04:48:40 pm »
I'm talking about brand new cars. The paint on them doesn't have a mirror finish. Actually my 5 year old car has a better finish than the new ones I saw in the showroom.
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