I've used a lot of both but I've never really tracked if one brand lasts longer than the other.
The primary difference that I know of), between the two styles of sanding discs are,
3M Trizact
Trizact dics start sanding immediately.
Meguiar's Unigrit
Unigrit discs have a break in time where the medium that emboidies the abrasives must break down a little to expose the abrasives and then they start cutting.
Here's a paragraph from my article written in 2010,
Damp-Sanding Tools, Tips and Techniques by Mike Phillips
B.I.T.E.
This is key remember…
BITE which stands for
Break-
In
Time
Efficiency
New discs
SKIM the surface until they break-in. A brand new disc requires anywhere from 2-4 passes to break-in before maximum cutting efficiency is reached. This has to do with physical process taking place on the surface of the paint and a physical process taking place on the surface of the paper.
Top coat hardness is a huge factor and
unknown variable between cars and effects how fast or how slow a disc will break-in. During the manufacturing process, the Unigrit abrasive particles are embodied in a slurry which hardens into a solid medium and this medium offers a controlled rate of break-down.
Efficient cutting is seen when the
water slurry on the surface is whitish in color. This is an indicator of clear paint particles suspended in the water film on the surface.
During break-in, the disc goes from
skimming to
biting or abrading... your job?
Pay attention to the task at hand.
This circles back to monitoring how much water you're using because a lack of whitish appearance to the water could mean the disc is either,
- Not broken in yet
- Too much water on the surface resulting in hydroplaning
- The disc is spent or used-up, that is the majority of abrasives have been worn off the face of the disc
The appearance for all three of the above is
clear water on the surface, so pay attention to the amount of water on the surface and how much area you've used each disc to sand and the concentration or lack thereof of the whitish appearance to the lubricating water.
