Hi ahpook,
Welcome to the Mattress Forum! … and thanks for the update.
[quote]One things we are disappointed is mattress developed 1" indentation where we sleep ( after 3 or 4 months). So there’s bump in middle that looks funny. I hear normal. But it looks funny.
I hear no need to flip top layer. So shall we just leave top layer as is and the bump is part of the deal with these latex mattresses? [/quote]
As durable as latex is … even the most durable foam materials will develop minimal impressions but 1" would be a little more than the norm.
There are really 4 possibilities that can account for impressions.
One is that some of it is coming from any wool in the quilting because wool will compress about 30% of its thickness over time. This can be evened out by sleeping on different parts of the mattress where you don’t normally sleep but it doesn’t generally affect the comfort of the mattress.
The second is your foundation under the mattress. If there is some flex or sagging on either side and the middle of the foundation is firmer (such as two twin foundations that come together in the middle to make a king or a foundation that has some flex on either side and a center support beam that doesn’t) then this can also affect the sleeping surface of the mattress.
The third is that the latex has “bunched” in the middle or isn’t lying completely flat inside the cover. This can be easily fixed by removing the layers and putting them back by flicking or waving them into position (see the assembly videos here)
Finally it’s possible that it is the latex itself although this would be unlikely. You can test this by taking out the individual layers (possibly when you are completing the previous step) and putting them on a flat surface such as the floor and then if you use straight edge or a string across the surface of the layer you can easily see if one of your layers has an impression that is deeper than normal.
You can see the rotation schedule I would suggest in post #2 here and flipping the individual layers in a component mattress (more the top layer than the deeper layers) can make some difference in how evenly the top layer softens over time.
Phoenix