Wet Sanding

[D]

This week I want to teach myself how to use my rotary and how to wet sand. I need to know what grit paper I should get, and where to buy it. I was thinking 1000, 2000, and 3000? And Im looking to get the Meguiars sanding block.

[ASPHALT ROCKET]

Mattos is in our area and have all that you need, also Total auto and Stohlman auto parts. I prefer 3m stuff, probably because that is what I started with 20 years ago. For what you are doing 1000, 2000, 3000 are good choices. I do not use a rubber block when I wet sand. Get the little rubber squagee and keep a spray bottle so you can keep the area you are sanding clear. If you ever need help just pm me since I am in the area.

[D]

Ill check those places out. Id definitely like to meet up sometime. Luckily Ive got a spare hood I can practice on.

[orngez]

go to the meguiars website and they have a dealer locator...look for ones that carry their professional line...usually they end up being body shop suppliers...i am like a kid in a candy store when i go to the shops...its fun...you will most likely have trouble finding 3000 grit...not a popular grit considering most polishes can easily remove anything 3000 grit can remove...dont bother with a sanding block or the meguiars sanding blocks..they are made for removing runs and sags from repainting....pretty harsh for anything as far as normal defect removal...

[mywifehatesclowns]

I actually tried my hand in wet sanding not too long ago...it was not as hard as I imagined...but I went into it with a clear mind and paced myself along the way and everything turned out great.

But it also was not a BAD scratch to begin with, maybe some more practice on my beater car.

[ASPHALT ROCKET]

Just a little tidbit, while wet sanding a there is a squeak type noise, that is a piece of debris between paper and paint. Squagee and look for the scratch it caused. Just take your time and no need to use alot of pressure. I learned on show and race cars. Friend of mine has a bodyshop and that is all he works on.

[Dust2Glory]

personally i would get 1000, 1500, 2000, 2500. dido on the block. pain in the butt do deal with in the first place. make sure you only rub back and forth along contour of body. after your first pass, spray the area down and make completely sure the surface is completely hazy, if not do it again, if so proceed to your next grit... the next paper should always remove the damage of the previous grit.

[D]

Yeah, I watched a video and a few tips from orngez. I think Im good to go.

As for the grits, you're right orngez. I really only need 1000- 2500. This is the block I was talking about, eBay Motors: Meguiars Hi-Tech Backing Pad 5.5"x2.5" E-7200 *NEW* (item 8057077214 end time Aug-08-07 18:36:57 PDT) (http://cgi.ebay.com/ebaymotors/Meguiars-Hi-Tech-Backing-Pad-5-5-x2-5-E-7200-NEW_W0QQitemZ8057077214QQcmdZViewItem)

One thing Im a little unsure on. Say I start with 1000 grit, and I remove the scratch. What do I do next? Move to another grit like 1500 or 2000? Then to 2500, then compound?

[ZoranC]

Check out Unigrit line. Also try to put your hands on some Mirka Abralon in 4000 grit becuse yes, you move through grits just like you do with polishes and smaller "gap" you have between last grit and compound easier it will be to remove sanding marks.

[ASPHALT ROCKET]

that would be correct. you want to get the sand marks as fine as possible.

[TOGWT]

Color Sanding / Polishing:
Years ago it was called coloursanding because automotive paints were single-stage (primer and a colour coat) and when the finish faded from ultra violet radiation (UVR) exposure, sanding off the oxidized paint thereby exposing the underlying paint would bring back the paint surface colour. Then, as now, most sanding was done wet so the terms colour sanding, wet sanding and as all these process involves a sanding block, block sanding all became interchangeable whether you were sanding for colour or for a level surface.

The secret to a Concours d'elegance winning paint finish is color-sanding (before wet-sanding paint show vehicle owners often have an extra 2.5 mils to 3.0 mils of clear applied).

This kind of work should only be undertaken by a very experienced enthusiast or a professional detailer, the paint sections / panels that are difficult and involve risk are usually those that are close to the edges of a panel (as this is were paint is usually thinnest) or highly contoured areas. Flat areas like the trunk, hood or roof involve minimal risk.

Wet-sanding levels the paint (and removes orange peel, harsh acidic or alkaline marks, etc) it removes approximately 0.025- 0.003 Mils (a Mil is 1/1000th of an inch) of paint from the vehicle using 2000 -grit finishing paper, Bear in mind that a clear coat has a thickness of 1.5 – 2.0 Mils, removing more that 0.3 – 0.5 Milsof clear coat may cause premature paint film failure. As a point of reference a sheet of Saran wrap measures 0.95 Mils



A digital paint thickness gauge will allow you to measure the film thickness of the paint system which includes the e-coat, primer, base coat (colour) and clear coat, total thickness is usually 4.0 – 6.0 Mils. Check the paint system both before and after wet sanding and this will tell you how much paint has been removed. For these reasons all car manufacturers now specify that the paint thickness be measured in 0.1mil, or 1/1000th of an inch before and after any wet sanding or buffing. The following are the maximum allowable clear coat reductions the major USA car manufacturers will allow: Chrysler – 0.5 mils; Ford – 0.3 mils; GM – 0.5 mils.

Product – Paint gauge; PosiTector 2000- De Felsko - http://www.dftinstruments.co.uk/p200/PosiTector200.pdf

Sanding Prep- wash paint surface thoroughly to remove any surface contamination, fill a spray bottle with paint cleaner/ degreaser (DuPont PrepSol II™ - http://www.xurex.com/products.html) to remove old wax and soluble contaminates, spray onto a 100% cotton micro fibre towel (DF Towels - http://www.dftowel.com/) and clean the surface. If you don’t wipe the surface before you sand you will not remove the contaminants, you will force (sand) them into the paint surface

Methodology
Put a drop or two of Woolite® liquid in a clean bucket and fill it with clean water. You will need 6-inch x 4-inch sheets of Nikkens™ 2000, 2500 and 3000 - grit finishing paper (1000 and 1500 grit is also available, but they are usually used on single stage paint systems, you can start with any grade of finishing paper according to the condition of your paint film surface, but as always use the least abrasive first) next cut or tear three or four pieces of the finishing papers in half and place them in the bucket also.

Leave them in the bucket of water for about 20 -30 minutes to soften their edges. Keep the surface wet at all times and sand in short strokes, applying light to moderate pressure with your hand or block held flat.. After going over the finish with 2000- proceed to 2500-and then switch to 3000-grit finishing paper and sand once more.

While you're waiting for the paper to soften, wash your vehicle too completely to remove any grit or dust, and then gently dry it with clean terry cloth towels. Next, take a tack rag and wipe over the paint surfaces one final time to make sure the paint is absolutely clean. A small particle of grit can make deep scratches in even the hardest finish. If you're working outdoors, wet down the surrounding area to keep dust under control, and keep a garden hose running with a trickle of water on the surface at all times.

Wrap a piece of the softened Nikkens™ (http://www.sherwin-automotive.com/products/show_product.cfm?product=1123)) 2000 - grit finishing paper (or whatever grade your paint surface requires) around a Unigrit Sanding Block (http://www.sherwin-automotive.com/products/show_product.cfm?product=1123)) (see also alternative products) if you're going to be working broad, flat surfaces. Otherwise, you can just fold the sandpaper in thirds. Keep wetting the surface of the vehicle in the area where you're sanding and keep it wet while you work. Place your hand flat on the sanding block / finishing paper at all times and start sanding in short, crisscross strokes. Avoid applying excessive pressure, keep the sanding block flat or you’ll gouge the paint surface and never sand with just your fingertips, as you'll create grooves if you do.

Only move the finishing paper and block about 4 - inches back and forth, if you do make a scratch, it will be a short one and easier to buff out. Using shorter, quicker strokes requires about the same amount of time as the longer sweeps most people are used to. Besides, you shouldn't worry about time and have a lot of patient when color-sanding. A clean rubber squeegee (3M™ Wetordry™ Rubber Squeegee, P/N 05517, 2 -inches x 4 -inches) is the best tool for checking your progress. Swipe the squeegee across the sanded surface periodically to clear it of water. Only when you have the surface completely free of any suggestion of orange peel or imperfections are you ready for the next step.

[TOGWT]

Proceed to the next level of grit and repeat the process until all the coarser scratches are eliminated and finish with 3000 - grit finishing paper in order to remove all of the very fine scratches, only when the paint has a consistently level, smooth, satin finish should you continue to the polishing stage. Final polishing (Menzerna Final Polish II) with a grey / black foam pad, speed 1200, and a machine liner speed (MLS) of 2- feet per second (FPS)

Bi-directional sanding- if you are sanding in a \\\pattern with the 2000, then sand in a /// pattern with the 2500, once all your lines are opposite then you know you have completely covered the area.
(See also Polishing, Spit Shining, Colour, Depth and Clarity, Legal Stuff, Wet Sanding / Polishing)

Caution- It is possible to wet-sand orange peel, but if you try to eliminate it completely you risk severely compromising the paint thickness. (See also Legal Stuff)

Note:Aluminium Oxide exhibits a high degree of friability. This means that when heat and pressure are applied it fragments. This is highly desirable because when it creates new sharp edges, this self-renewing property allows aluminium oxide to last longer than most other finish papers.

Reference source- Eastwood Technical Library - http://www.eastwoodcompany.com
Glasurit,Advice on Paint and Paintwork Defects (http://www.glasurit.com/Service/AdviceOnPaintDefects/) - Glasurit (http://www.glasurit.com/Service/)
Color Sanding and Polishing - Welcome to System One APS., System Ones products official web site for all your System One needs, The fastest way to polish paint. (http://www.systemoneaps.com/new%20for%202006.html)

Alternative products -Water-fed Soft Block - http://www.wetwedge.com/wfsoftblock.php (http://www.wetwedge.com/wfsoftblock.php)

[D]

Awesome! Thank you.

[ZoranC]

I would like to add another "Thank you"

[Al-53]

Great write up...very informative and right to the point....

Thanks Jon


AL