Tuesday, September 30, 2014

Cutting and buffing: Part 1. Cutting

Warning: what I'm about to describe is not for the faint of heart.  However, it is the method used by some of the best and most meticulous painters I know in the industry.  And it will take you hours and make you hate your life.  It has taken me hours and makes me hate my life.

In fact it is so bad that it has taken me almost a year to cut and buff my car.  And my car had hardly any orange peel; it was pretty darn smooth.  Also, I'm lazy, not motivated, and hate this.  So that makes it really hard to get out there and do it.

Well, here it goes.

Depending on how much cut is needed, I will start with 1000 grit, then go like this: 1200--1500--2000--2500--3000 Trizact on DA, and then buff.  1000 is wet with a hard block.  1200-2500 are wet with a soft block.  The paper I am using is Meguiar's Unigrit, which is actually made by Nikken.  The 1200 is Indasa, who I forgot I loved their paper.  Consequently it's the same price as the Meguiar's paper but for 50 sheets instead of 25.  I think the Indasa paper is really great.

And then I buff.  The buffing is done on a rotary buffer with Chemical Guys V-series compounds.  I buff with two different compounds--first V32, then V34, and then polish with two more compounds--first V36 and then V38.  For the compounds I am using a 6.5" orange Hexalogic buffing pad I purchased through Chemical Guys.  For two polishes, I switched to the black Hexalogic buffing pad.   I am also using Chemical Guy's flexible backing pad.  All of this (for the buffing material) ran me $200-and some change, but it's great, great stuff, and best of all, smells delicious. 

Oh, it smells so good.

For buffing pad lubricant, I'm using Chemical Guys buffing pad lubricant, which smells like liquid bubble gum in a  bottle.  I'm not even kidding.

For buffing pad wash, I'm using Chemical Guys buffing pad wash concentrate.

Other necessary materials required are:
  • California Duster (this is to clean dust off the car before working on it
  • Two buckets for washing (a clean bucket, and dirty bucket)
  • Microfiber washing mit
  • A CLEAN bucket and lid for soaking sand paper.  I went and bought a brand new 5 gallon bucket and lid for this purpose, because I wanted it to be so clean.  And the lid keeps it clean.
  • A spray bottle
  • Dish soap (for lubricant)
  • Sanding block set ( I was using select blocks from my Durablock set)
  • 6" long piece of 3/4" PVC pipe or electrical conduit, with the edges sanded smooth (you'll see why)
Cleanliness of everything during this process is so critical.  Cleanliness of the water.  Cleanliness of your clothes.  Cleanliness of the bottom of your squirt bottle (don't let it sit on the ground).  Cleanliness of your hands.  Cleanliness of your panel.  I use fresh, clean softened water in my squirt bottle.  I have a dog and cats so I put on a clean shirt when I go out to sand so I don't have any hair that falls off me and gets scratched into the work.  I keep my squirt bottle hanging off the side of my bucket so the bottom doesn't get grit on it from the floor and then find its way to the work surface.  I keep my hands cleaned and sprayed off so they don't collect grit.  I keep the sandpaper sprayed off frequently.  I think you get the idea.  A tiny piece of a foreign particle finding its way under the sand paper will make a nice rogue scratch you did not intend to be there.

By this time, any runs should already be removed, and I've already described how I did that in an earlier entry.

I just focus on one panel at a time, start to finish.  I first dust off then wash the panel.  I tape over body lines + about 1/4" extra, and tape over body gaps to keep water and sanding mud from running in there, and to protect the adjacent panel.  By this time the sandpaper should be soaked in water for a minimum of 15 minutes; in reality, my sandpaper is soaked for days as a sheet or two of each grit just lives in the soaking bucket, and I freshen up the water frequently. 

If the panel has a lot of urethane wave (where the clear coat looks kind of squiggly and wavy) I start with 1000 grit on a hard block.  I notice urethane wave the most where the lighting wasn't adequate and I really hosed too much clear coat on, or else I was cramped and holding the gun too close and hosed on the clear.  Either way, the good thing is there is a lot of mil build of clear there so it's forgiving to remove a lot of material.  I constantly spray the panel with sudsy water from the squirt bottle, sanding in a back and forth motion, front to back.  The sandpaper needs to be sprayed off frequently as well to clean off the sanding mud.  I avoid sanding in a diagonal pattern and I move in a front to back motion that follows the panel.  The reason is, if you don't get good enough scratch cancellation or don't buff thoroughly, diagonal scratches pop out much more than a scratch that runs along the direction of the panel.

One of the most important things to sanding is silence.  Silence is so critical because you need to be able to hear that little piece of grit that gets stuck under your paper.  It will make a high pitched squeaking sound, and you'll get real pissed every time you hear it.  Sand with some music on and you could be working that grit along the panel the entire time you were sanding it.  Which is another benefit to frequently spraying down the panel and paper.

When I start a new panel, I've found the sandpaper really tells you how much more it needs to be sanded based on the sound and feel.  When you first start cutting the clear coat, it feels real slick, hard, and bouncy as the sandpaper just wants to glide over the top.   Eventually as you cut in the feel changes to a little more controlled, with more friction, which means you've broken the skin of the clear.  I also just use real light pressure.  Almost just the weight of the block and let the sand paper do the cutting without me forcing it.  This is also safer in case a piece of grit finds its way under there.  I can also physically feel high and low areas in the clear where I've cut it flat and where it needs to be cut flatter.  It will still feel thick and wavy.  The other piece to this is I've also found when moving to a finer grit of paper, you'll feel less and less resistance in the paper as you remove material and have sanded away the larger grit scratches.  This is also accompanied with a change in sound of the sanding.  I noticed the sound changed from a 'coarser,' louder sanding sound to a 'finer' quieter sanding sound as the larger scratches got cancelled and the surface becomes one uniform grit.  I have started using these as guides to know how long I need to sand an area.

Stay away from corners and edging when sanding, these are easy places to break through.  If you do break through anywhere, you are re-basing that spot, and then re-clearing the entire panel.

To get into the compound curve areas, I use my 3/4" round PVC hardblock with the ends sanded smooth to a bevel, and wrap the paper around this.

When I think I'm done with 1000 grit on a bad panel, I blow dry it off, and this will reveal any imperfections that need to be sanded more.  I don't try to completely remove all the orange peel on the first pass.  Keep in mind there are still going to be a number of other grits to follow, and all will remove material to some degree.  This approach keeps more clear on the car.

If I'm done, then I move to 1200 grit, and this is for the sake of cancelling out the 1000 grit scratches.  Here what I've found works real well is to take a soft block (such as a 3x5 block) and use an old 3M Trizact pad cut to the same size as the sandpaper as an interface pad.  I put the sandpaper over this and hold both of them to the block as I sand, using the same techniques as before.  When I switch to the roundblock, I just wrap the interface pad/sandpaper halfway around the block and start sanding.  1200 is the grit I normally start with if there is just regular surface imperfections such as dust nibs and only minor orange peel.

After this it's the same thing all the way up through 2500.  Expect to take a lot of time with the 1500 and the 2000.  The grits at this point are getting very fine and becomes more difficult to cancel out previous scratches.  And before every new grit, the panel gets washed off and cleansed of sanding mud.

Finally, after 2500, I move to a 6" 3M Trizact 3000 pad on an electric DA polisher with an interface pad.  An interface pad is a soft pad about 1/2" thick with velcro on both sides; one side of it sticks to the backing pad of the DA, the other side is what the Trizact pad sticks to.  This interface pad allows the sanding pad to conform to the surface profile of the car better. 

Sanding with 3000 will remove all the sanding striations and make it have one uniform, 'scuffed' look; in fact it will have a slight gloss to it.  This sanding is done quasi-dry.  The pad should just be damp, and the panel should be dampened with a few spritzes of water.  Too much water and the pad won't do its job.  I sand at a medium speed, move slowly back and forth across a section of the panel, overlapping by 50%.  The more time I spend here with 3000, the easier time I have buffing, so I go back over myself 3-4 times, switching between going back and forth across the panel to up and down along the panel.

At this point it's a very happy point, because I've now probably got several hours (or more) into sanding the panel, and now it's ready for buffing.

But I'm not going to lie, I am so tired of writing this up I'm going to end it here and pick up on buffing at another time.

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