Very interesting threads below on layering of waxes and sealants:

layering of waxes
layering of sealants

The person doing the testing used scientific equipment which can measure down to sub-nanometer level to determine if waxes and sealants layer, and if they do, how many you can add before adding anymore would be a waste of product.

General conclusions (if I've understood the results correctly) are that:

  • Adding a second layer of wax can have a positive effect, but mainly because it ensures that the surface has an even coating of wax - i.e., the first layer may not be completely even, so the second layer ensures that these "valleys" get properly coated.
  • It is important to adhere to drying times - i.e., ensure that the wax does haze and dry before buffing it off.
  • Adding additional layers of wax beyond the first two do not provide any benefit - in fact, because of the need to buff these layers, you actually reduce the thickness of the wax that you previously applied!
  • Sealants do not seem to layer at all.


Of course, the results do need to be taken in the proper context - the tests were done on silicon wafers (used due to their incredible flatness) rather than metal with paint and clearcoat, and different sealants may have different properties from the ones tested; nonetheless, a very interesting read, and it shows that you shouldn't overdo things, as doing so can actually be counterproductive.

Oh yes, take a look at the thickness of the sealants and waxes that remain - just 20nm! (20 nanometers is 1/50th of a micron, and a micron is about 1/100th the thickness of a human hair.) This supports the idea that the biggest part of detailing is about the preparation of the surface, rather than what we place on top.