Hi EZ4HZ,
There is more about the differences between blended Talalay and all natural Talalay in post #2 here. In an apples to apples comparison (where all the layers were the same ILD) most people wouldn’t feel any difference in a single layer but some people would feel a difference if a whole mattress was made of one vs the other (although many still wouldn’t).
“Pushback is somewhat of a misnomer because when you are lying on a mattress all the downward and upward forces are in equilibrium and there isn’t a “direction” of the forces involved (your body “pushing down” or the material “pushing up”). The resistance of a material is a combination of the ILD which measures the force it takes to compress a 6” latex core by 25% of its thickness (or 1.5" ) and compression modulus which measures how much firmer the material becomes with deeper compression after that (between 25% compression and 65% compression which is 3.9") but with foam materials the compression curve isn’t linear and is in more of a banana shape (see here).
What you actually “feel” when you are lying still on a mattress is the varying pressure against different parts of your body (which us usually measured in hhmg).
Latex is also very resilient (which is measured by dropping a steel ball on a material and measuring how high it bounces) and this is also connected to the feeling of “pushback” that some people describe. Materials that have more resilience store more of the energy of compression and less of the compression forces are absorbed (called hysteresis) but you can only feel resilience when you move on a mattress (vs lying still) and feel the “bounce” or “spring” of the material. Steel springs for example are the most resilient mattress component because they absorb less of the energy of compression and “store” more of the compression forces than foam materials (including latex).
Phoenix