Too many re-sellers claim all over the internet that “high density foam” (pink, green or grey) is used to manufacture the couches they have on offer. I cannot deny the fact that some (few) manufacturers do use it, but the great majority actually use at best a “medium density foam” (yellow or brown) which is still acceptable, provided the users do not exceed 90kg. But the reality is that many actually use a “low density foam” (blue or white) and tit is a serious concern.
You will notice that I mentioned next to each density the most common colors found for each density. So all you got to do now, is to unzip the seat cushion and see for yourself what is in there.
But here is the trick; most manufacturers who use lower density foam, manufacture their product with fixed seat (built into the frame). It is also a way for them to use less fabric.
Despite the fact that you won’t be able to see what type of foam was used, the main concern is that if the foam collapses and it will eventually, even when a medium or high-density foam is used, you will not be able to replace it yourself. You will have to take it to a re-upholsterer and the cost involved will be higher than purchasing a new couch. The other advantage of a loose seat cushions is that you can turn it around frequently to increase the life span of the foam. I would therefore recommend if you want to keep your couch for a long period of time, that you buy one with loose seat cushion.
Remember that most manufacturer excludes “fabric and filling” in their warranty. It is therefore very important, if you or someone in your family who will be using the couch ways more than 90kg, that you disclose that information to the seller. You should rather pay a little extra for a higher density foam to be used at once than having to replace the it in the next 6 months.
Another very important aspect of foam, apart from the density, is the firmness or hardness. Low density foam is usually very soft, and high-density foam very hard. That said, it exists a premium product, much more expensive,which has a high-density but also very soft. Some call it SS (super Soft) others LHL. A “comfort layer” of 1 inch of that product can be added on top (and bottom when the seat cushions are loose) of the primary foam to add softness to the final product.