What's the difference between wet sanding and dry sanding using a DA polisher ?

[asalah]

I'm ordering some 6 inch 1500 grit sanding discs to use with my Meguiar's 110v2
And I'm wondering about the difference between dry & wet sanding using a DA polisher

My assumption is that one must start dry, then go wet for an easier to buff finish

Is this correct ?
Also why there are no 6inch sanding discs more aggressive than 1500grit ??

Thanks in advance

[greg0303]

Re: What's the difference between wet sanding and dry sanding using a DA polisher ?

1. Wet sanding - sanding by hand using sand paper which gets presoaked (at least 15 minutes in advance) in mix of water and car soap, intense amount of water is used in this method, wet sanding on single stage paint is called color sanding;

2. Damp sanding - sanding using circular sanding discs and D/A sander (either electric or pneumatic), only mist of water is needed per section.

When damp sanding using electric D/A polisher with Meguiar's Unigrit sanding discs is performed couple steps must be taken:
- use S6BP backing plate with 6" discs and S3BP with 3" discs,
- medium tool speed works best, like 3-4,
- use electrical outlet with ground-fault interceptor, water is being sprayed around electric tool so some precaution is definitely needed,
- little down pressure needed while damp sanding,
- foam interface pad will provide uniform sanding.

[Michael Stoops]

Re: What's the difference between wet sanding and dry sanding using a DA polisher ?

Wet sanding refers to what people generally think of when considering a traditional wet sanding process; the abrasive media is designed to be soaked in water for a period of time prior to use (usually 24 hours) and then the surface being sanded must be kept very wet all the time. Often a bit of soap is mixed with the water used in this process.

Damp sanding, on the other hand, uses much less water and does not require that the abrasive media be soaked overnight prior to use. In fact, media designed for damp sanding, like our Unigrit Sanding & Finishing discs, should not be soaked at all prior to use. When you are using this media you only need a couple of sprays of water on both the surface to be sanded and on the abrasive media itself for each section pass. Too much water, or too much speed on the DA tool, will create a hydroplaning situation where the media will lift off the surface and cut will be lost. Oh, and no soap is to be used in this water when damp sanding, either.

A few other things to keep in mind when finish sanding with our Unigrit discs and a DA sander (whether air powered or the G110v2):

• You should always use a foam interface pad between the abrasive media and the tool. This allows the media to better conform to body contours, minimizing the risk of cut through
• We offer both finishing discs and sanding discs:
  • finishing discs are essentially the abrasive media bonded to a film with a thin layer of foam between the film and hook & loop attachment layer
  • sanding discs are similar to finishing discs but lack the foam layer and so will cut will be increased - yes, that means that a 1500 grit sanding disc will offer more cut than a 1500 grit finishing disc
• Faster speeds on the DA sander will yield less cut than slower speeds will - slower speeds will allow the abrasives more time to cut deeper while higher speeds can create a hydroplaning action, especially if too much water is used.

As to why we offer nothing coarser than 1500 grit in 6" size - these discs are designed for finish work and/or to reduce or match orange peel, or to eliminate severe scratches and other defects in paint. A 1500 grit sanding disc should be sufficient to quickly and safely eliminate excess orange peel or other issues arising in the painting process. A 1500 grit finishing disc should be sufficient for quick contour matching, or elimination of other defects arising during the painting process will retaining texture in the painted panel that matches surrounding panels. A follow up with 3000 grit finishing media will refine the sanding marks to the point where rotary compounding will quickly, safely, and easily remove all sanding marks and leave the gloss level desired. Follow up with a final polish using a foam polishing or finishing pad, of course.