Horse Feathers (Charter Member)
Posted - 17 Sep 2018 : 11:04:22 AM
| Tips on "Cutting and Buffing" Clear Coat
(These tips follow the shooting of base coat and clear coat)
Cutting refers to the use of wet or dry sandpaper using water and the fluid to remove imperfections in the cleat coat. It can be done manually or by using a machine. These tips apply only to cutting by hand.
The water must be clean water and may be applied to the surface using a spray bottle or a clean, new sponge. I prefer the spray bottle as dropping the sponge once and it's over--get a new one.
A clean bucket of clean water must also be used. This water is used to dip the sandpaper to get it fully wet before sanding the surface.
There are at least two hand held pads that should be used in the cutting process. One is stiff the other is flexible.
The grit to start wet sanding depends on how smooth the clear was laid down. If there are noticeable particles of dust and considerable orange peel, starting with 1000 may be correct. If, the clear came out very smooth with little dust or orange peel to remove, starting with 1200 or 1500 may be perfect.
A half sheet of paper should be wrapped around the stiff pad. No need to cut it into 4ths. Wrap it around the stiff pad so it is tight, dip the pad into the clean bucket of water, and apply a sprits of water to the surface.
Work the paper in one direction, do not sand in different directions. No helter-skelter movements. Take your time and allow the paper to cut into the clear. A whitish, milking slurry will occur.
To check how the sanding is going, you will need to use a squeegee. The squeegee is used to draw the slurry off the finish. When things look right, the swept area will be flat with no highs or lows noticeable. If there are highs and lows, more sanding is necessary. Check repeatably. Once the finish is flat, proceed to the higher grit sandpaper like 1500. Do the same thing, repeat, using the flexible pad. After this move up to at least 2000 grit and sand and check with the squeegee. The stiff pad levels the surfaces. The flexible pad does not. Use the flexible pad around ridges and edges to avoid removing too much clear from these exposed areas.
Buffing is performed after wet sanding as stated above. I've used wool pads in the past and have had good success with them, however, wool pads and cutting compound is very problematic around ridges, corners and edges. A few turns of the pad at the wrong angle can easily cut through the clear, base coat and into primer. My personal choice is to be safer and use modern foam pads designed for cutting and polishing. The foam pads have different textures. The more rigid foam pads are for cutting while the soft foam pads are used for polishing after using cutting compound to remove sanding marks. The goal is to remove evidence of wet sanding--eliminate all unwanted sanding marks. Impossible? No, it can be done.
I have used the lambs wool pads using a direct drive variable speed polisher-sander. With the foam pads, I use a Porter Cable Model 7424XP Random Orbital polisher. It is light weight and speed can be dialed in from low to high. I have a "Velcro" set up so the foam pads are easy to attach and remove from the machine.
Slow speeds are suggested when starting the buffing. Apply several dabs of creamy compound to the foam pad and smear some of the compound on the surface to be worked. With the machine dialed in to a low speed, with pad on surface, start the machine. Work the machine in right angles, back and forth, than up and down. After a while increase the speed...continue using the same pattern and slowing increase the speed of the machine after several passes. As you do so, you will begin to eliminate the compound and the luster of the refinished surface will begin to come out. When you think you've done enough, use a clean microfiber cloth, preferably a new one and wipe and rub the remaining compound off the surface. If the surface doesn't look like glass, do more buffing. At some point you will stop buffing to move on to polishing.
Polishing uses a very mild abrasive and brings out the high luster the clear can deliver. The polishing process is similar to the buffing with compound process. Polishing also adds a marginal layer of protection to the surface. Waxing the surface provides the final protection from assault from the sun and other air and water borne contaminants.
I hope these tips prove helpful to you.
Questions? Please ask them.
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