Hey Woolford13,
@Latex Mattress Factory is 100% correct.
Generally speaking, the 20-24 ILD will “feel” softer to most people than the Arpico D60. It will not feel firmer, I am quite confident of that point. And for some additional light reading:
Dunlop and Talalay aren’t directly comparable in terms of firmness using only ILD numbers because there are several factors that can affect how soft or firm a mattress (or an individual layer) feels besides just the ILD of the material (see post #4 here). Dunlop and Talalay that are the same thickness and ILD won’t feel the same in terms of their firmness for most people because they have a different response curve and compression modulus (how quickly a material becomes firmer as you sink into it more deeply). There is more about the difference between Dunlop and Talalay in post #7 here.
Moreover, the ILD of different materials or different types and blends of latex also aren’t always directly comparable to each other (see post #6 here ) partly because ILD can be measured in different ways and partly because ILD isn’t the only factor that affects the softness or firmness of a material so again using the ILD or other specifications of a particular layer or combination of layers as a reliable indication of how any mattress will “feel” or how firm it will feel to you compared to another mattress with a different combination of layers can sometimes be more misleading than helpful.
Thanks
Sensei