I’m curious to know exactly what types of foam or other dense material is used to pad this type of sofa? i can’t imagine there are any springs inside this.
Its in polyurethane foam. Practically all upholstered furniture is now done with this stuff. There are many different densities so that the bottom of the cushion can have a higher density than the top one while the top layer can be a softer lower density. Then they are glued together and upholstered allowing cushions and anything else to keep there form while keeping it relativly soft.
I was working on a sofa last year that had about 5 different densities. The different densities come in different colours just like hard polyurethane for modelmaking.
Stefan Krivokapic
co-founder of Fraktal
http://www.fraktal.it
is polyurethane foam an expensive material?
one more question while we’re on the subject of upholstery, can you or anyone else give me the process by which prints are made on the fabric? i mean is it possible to print stuff permanently on the fabric (be it muslin or canvas or whatever) and not fade? or are the designs ALWAYS sewn right in at the time of making the material?
Expense is relative, and there is no alternative to compare with for this kind of upholstery. Blown fiber, goose down, etc. won’t hold shapes like poly foam. I guess you could use horse hair… 
I’d say that the Blu Dot sofa is all foam. It could have some kind of low-profile seat springs (sinuous wire) or elastic webbing, but that is difficult to gauge from a photo.
You can make seat cushions with springs inside them, like this.
PU foam is not that expensive. it is cheaper than molding foam. layering foam by gluing pieces together is very common.
you build up foam pieces and sculpt them subtracting what you don’t want. usually all that is needed is an electric carving knife (like for carving turkeys), a rasp and a grinder for blending.
sometimes springs or wire forms can be added under the foam. you can use these to secure pulls or tucks through deliberate cuts in the foam. this is common in automotive upholstery where a wire may be insert molded into the foam to accentuate the cut and sew…like bolsters and pads.
usually the foam is made first and the upholstery is cut to fit it. a layer of muslin or batting is necessary between the foam and the fabric to prevent the foam from grabbing the upholstery.
man you guys are always full of such detailed technical answers… i swear i get better responses on core than I do in school. seriously. posting on core should be made mandatory for any product design major.
About upholstery, are there still in existence, any US-based companies that will supply this service on a small scale?
There are still quite a few little upholstery shops around, especially in the older, established parts of cities. There are still a few people left (mostly old people) who will have a sofa recovered rather than stick it on the curb and buy another disposable one from IKEA. Quality at these shops can vary a lot though.
upholstery shops are local and pretty easy to find. usually a perspective sketch of the cut and sew is very helpful for the tailoring. i also drew right on the finished foam where i wanted the seams and pulls to be.
i learned to sew my own covers later on an industrial grade sewing machine. (watch your fingers…seriously)
actually, i’ve found some of the best upholstey shops by asking hotrod owners or car restorerers.
foam: because i know you will be in the area soon, grand rapids foam on alpine
thanks KF Jesus & mr. Benett, sorry didn’t notice that your reply until today.
the GR link is def what I’m looking for. Didn’t know upholstery was THAT easy to find… I seriously thought China would be the likeliest spot.
btw. i moved to GR in July… Love it here!