The Fundamental Variables of Paint Polishing:
Pt 2 – Pad Pressure
By Christopher Brown of OCDCarCare Los Angeles – OCDCarCare.com
Pad Pressure is defined as the amount of force applied to the machine [which transfers to the pad via backing plate] other than the weight of the machine. Often this is referred to as downward pressure. Because many vehicle panels are vertical, and the machine isn’t always pressed in a downward fashion, therefore term is not used here.
Pad pressure is important during paint correction because it drastically increases or decreases the level of friction which the pad and buffing liquid engage the working section. Firm pad pressure is a simple and effective way to increase the total aggressiveness of a machine, pad, and correction liquid combination. Firm pressure also causes the pad to completely engage the surface, fully realizing the ability of the pad to push away paint residue.
Pad Pressure, Heat, and Clear Coat: A BAD Combination!
Heat is the immediate byproduct of friction. Therefore, when pad pressure is increased, the greater the amount of heat generated on a working panel. This is a factor that ALWAYS needs to be monitored since modern vehicles contain many different substrates. Some of which heat up very quickly and do not dissipate heat well.
Speaking of heat, modern clear coats are catalyzed and do not respond well to mechanically generated heat. Contrary to some popularized beliefs a catalyzed clear coat’s tolerance for heat is not high, nor is it forgiving. Clear coat cannot be heated to be reshaped, reformed, or “reflowed” in any controlled manner.
As clear coat quickly heats from abrasion, it reaches a tipping point of becoming too hot. Once the clear coat passes its chemical ‘heat threshold’ and becomes too hot, a burn through can occur in a split second.
A high degree of friction from modern buffers is easily obtainable if too much pressure [friction, and thus heat] is focused in a particular area for too long.
While this statement is truer of rotary polishers, it is also a reality with contemporary DA orbital machines such as the Rupes 21 & Rupes 21 MkII and the Flex 3401 with its forced rotation. Modern paint polishers combined with aggressive combinations of backing plate, pad, and product mean paint DEFINITELY make it possible to burn paint in a moment’s notice.
Each Vehicle (Paint System) Reacts Differently to Paint Correction
Every vehicle reacts differently to paint correction processes because environmental factors and owner care habits can greatly alter the paint characteristics of a vehicle throughout its lifespan.
For example, imagine two exact vehicles, 5 years old, painted back to back in the same factory. These two identical vehicles may react completely different to paint correction steps.
- Car A lives in Arizona as a primary daily driver, living outside 24/7 in the intensely hot desert sun. Also, the vehicle receives little to no surface care, allowing the elements to wear the clear coat dangerously thin.
- Car B lives southern California and is a weekend cruiser/garage queen. Vehicle B’s owner enjoys maintaining his vehicle, adding protection three times a year. The paint on vehicle B has been maintained impeccably.
An Improved Guideline for The Amount of Pad Pressure to Use During Paint Correction
With the Car A & B example, it is easy to understand how vehicle surface care can alter the characteristics of paint over time.
Car A could have any number of issues such as: much harder paint, heavy oxidation, greatly reduced amount of clear coat, low amount of U.V. inhibitors, among others. This is the primary reasoning which explains why all vehicle surfaces REQUIRE different paint correction approaches.
Since every vehicle paint system differs, therefore an overall guideline for pad pressure amount is as follows.
“ Use as much pad pressure as needed to assist the pad and the buffing liquid to optimally work the painted surface according to its intended purpose.”
This pad pressure philosophy accounts for all factors of surface correction such as:
- Final Polishing,
- Extremely thin paint
- Prior work done to the paint
- Resprayed Panels
- Varying levels of defects
In this methodology, use enough pressure to get the job done without: too much aggression, the removal of too much paint, and/or creating too much heat.
© Christopher Brown – OCDCarCare Los Angeles – OCDCarCare.com – 2013
Click here if you missed Pt. 1 of the series: Introduction & Variable 1 – Pad Angle
For more interesting topics on: auto detailing, paint polishing, and car care please browse: OCDCarCare Los Angeles’s – Detailing Article Archive.