Let's talk about "Total Cut"

[Michael Stoops]

There is a lot of discussion about how aggressive one product is compared to another, often between products that aren't even designed to do quite the same task. Many of you have seen the cut scale shown on the side of most Mirror Glaze products but you may not be clear on just what they mean.

On the bottle of M105 Ultra Cut Compound you can see that the arrow goes all the way to the top - that's a 12 on the cut scale. But the M205 Ultra Finishing Polish and M80 Speed Glaze only register a 4 on the scale. Obviously then, M105 provides more cut than either M205 or M80.

But what does that "12" or "4", or any other number, really mean? Will they always provide that much cut? Isn't a "12" way too much cut when all I want to do is remove some light swirls? Should I use maybe something that registers an "8" or "6" instead?

You may have noticed that we do not provide a cut scale on our consumer products, and that is simply because there are just too many variables when dealing with the average consumer. And variables are what this article is all about.

* NOTE: the above scale is not intended to be a precise quantitative indicator of changes in cut but rather simply of visual indicator that a change in cut exists. How much more or less cut any given product can achieve is dictated by a very wide range of variables.

Looking at the chart shown above, we see that the "Total Cut" is greater when a product is applied by rotary buffer than it is when applied by hand, and that G110 (D/A polisher) "Total Cut" is somewhere in between the two. You can also see that, for example, M105 always has more cut than M205 when used the same way. Not surprising since, as has been pointed out, M105 is a "12" while M205 is a "4". But even that doesn't tell the whole story.

The key here is that phrase "when used the same way". Let's just look at polishing with a G110 using M205, but with two different processes.

Here you can see that Process 1 pairs M205 with the less aggressive pad, it's run at a less aggressive speed, and less aggressive pressure is being used than with Process 2. The net result is that Process 1 will provide less cut overall than Process 2, even though the same M205 is being used. It is the combination of variables that determines "Total Cut".

Some of the variables can have a sizable impact on total cut. When working with a rotary buffer if you move from a W8207 Soft Buff 2.0 Polishing Pad to a W5000 Double Side Wool pad, without changing machine speed or liquid, you will get a a huge jump up in total cut. The ONLY thing you changed is the pad. Or keep the liquid, the pad and the pressure the same, but change the speed of the rotary from 900 rpm to 1800 rpm and you'll get a sizable jump in total cut too. And all you did was run the machine at a higher speed. The G110 will return a similar change in total cut when doing the same experiment - same liquid, same pad, different speed - but the total cut will still be lower than that of the rotary buffer. That's because the machine has become a variable too, and a sizable one at that.

How extremely can you alter total cut when taking many variables into account? Try using M105 (cut rating of 12, remember) on a G110/W9207 Soft Buff 2.0 Finishing Pad/Speed 3/5lbs pressure and compare the total cut to M80 (cut rating of just 4) on a rotary/W5000 Double Sided Wool Pad/1800 rpm/5lbs pressure. Total cut on the M80 under these circumstances will be greater than the M105 combination cited above. (NOTE: you would probably never run M80 in this configuration - in fact, it isn't officially recommended by Meguiar's and is described here for illustration purposes ONLY)

At the risk of making this even more complicated, let's take a quick look at pad size when machine polishing. The increasing popularity of 4" foam pads has brought about a major variable. Sure, they make it easy to machine polish in smaller, tighter areas but they also alter the total cut. On a rotary buffer a smaller pad actually provides less cut (assuming similar foam construction, speed and pressure) because the speed at the outer diameter is lower than with a larger pad. We've already established that with a rotary buffer more speed equals more cut, so this slower speed at the outer edge of the pad falls right into that equation. On a D/A polisher the opposite effect results - a smaller pad gives more cut (again assuming similar foam construction, speed and pressure) because the energy is concentrated in a smaller area. The prevailing notion that you can not burn through or otherwise damage your paint when using a D/A needs to be reconsidered when using small pads. We've seen people damage paint while using a 4" cutting pad on a D/A running at maximum speed with a strong compound. When you compare that combination to a standard 6" or 7" pad with a mild paint cleaner used on speed 5, the increase in total cut is quite dramatic. It wasn't very long ago that this combination of small pad/high speed/aggressive compound was quite rare, but it's becoming more and more common place. And if you aren't thinking about how your changes effect total cut, you could be in for a surprise.

Probably nowhere is the concept of variables dictating total cut more fully experienced than when using M86 So1o Cut & Polish Cream. M86 was developed specifically for use on fresh paint, primarily in a body shop environment, and is truly part of a "system". The system is comprised of a single liquid and four different pads; a heavy wool cutting pad, light wool cutting pad, foam polishing pad and foam finishing pad. The idea is to use the liquid with one of the wool cutting pads to eliminate sanding marks, an initial cutting step done at fairly high speed - something on the order of 1500 to 1800 rpm. You would then follow with the foam finishing pad to remove any holograms or light marring, and then finish off with the foam finishing pad at a speed as low as perhaps 900 rpm to obtain a flawless finish. The very same liquid used to pull out sanding marks will also provide a flawless, highly reflective finish? Because of the variables involved and their impact on total cut, yes.

So next time your goal is to remove defects from the paint, consider not only which paint cleaner or compound you'll be using, but how you'll be using it. You choice of machine, speed, pad construction, pad size and pressure will all impact how much cut you'll get out of the liquid.

One last thought - just because a certain combination of the above variables worked on your friend's or neighbor's car does not guarantee the same result on your car because, you guessed it, the paint itself is a variable! And you wonder why this is often referred to as "the art of paint polishing"!

[TH0001]

Absolutely TOP NOTCH article Michael... VERY NICE! Thank you for putting this together for us!!!

[ClearlyCoated]

Another well thought-out, well written MOL thread for my saved links folder!

Thanks Mike!

[Dan Fisher]

I Would not want to be the one to make that mistake with the small pads, high speed, heavy pressure!!! Outstanding article Mike, as already said one to keep for future referral !!!!!!

[Hemin8r]

Great job putting this together Mike. This here really does give a good idea of how many variables there are.

[Bunky]

Great chart !!!!!

[Mikejl]

Mike,

Excellent chart! Very clear and nicely put together.

Mike

[73corvette]

Michael,
I'm a consumer not a detailer, but I'll tell you in doing mt vette I am learning a lot why the good detailers get the big bucks and I am also gaining a lot of experience by doing this myself, who said you can't teach an old dog new tricks,lol. I would have never tried this if it weren't for this forum and all the knowledge and help that I've received from all the guys on this forum and I thank all you very much for the for the kind reception that I received here.
You guys are the BEST!

Rich

[irf@n]

Great guide!

[Mark Kleis]

I'm really surprised this hasn't gotten more replies...

This took a tremendous amount of meticulous research and work, and more importantly, it points out some very key concepts to paint correction that are often misunderstood, or missed completely by amateurs just getting started.

This is the type of guide that is worth getting printed out at Kinkos, laminated, and stuck in your detailing bag to stay with you where ever you go to detail.

Well done Mr. Stoops!