Do ILDs change?

[phoenix]

Hi Gail J.

Will the ILD of a NR latex core soften enough that it’s ILD rating changes?

Any change in firmness (even the smallest) would change the ILD of a material to some degree but ILD ratings aren’t exact and are inside a range anyway so it would normally still be inside the same ILD range. Most people wouldn’t notice ILD differences that are about 3 ILD or less anyway.

Is there a break-in period on a new mattress where the latex softens in the first few weeks, or does the softening process take years?

There will be an initial break in period with any new mattress or foam material (including latex) over the course of the first few weeks after which any changes would be much more gradual over a longer period of time (see post #3 here).

Would a 3 layer (3" cores) mattress of medium, firm and extra firm all change to a softer feel or just the top layer?

The regular deflection/compression of a foam material is what softens or breaks down foam over time and softer upper layers of a mattress will deflect and compress more deeply and more often than firmer deeper layers so foam softening will happen more with softer layers and/or layers that are closer to the sleeping surface than with firmer layers or layers that are deeper in the mattress. Latex in general though is the most durable of all the foam materials so foam softening and break down will generally happen less and more slowly than with other types of foam.

Phoenix