Originally Posted by TheSkiGuy
Foam liners look very much like the normal liners that come in your boots. However, instead of having generic, non-custom material inside of them, foam liners require a bootfitter to "shoot" foam into the liner while the user is wearing the boot in the shop. The foam comes in two containers and the liners have tubes that allow the liquid foam to enter through the rear of the liner and any excess to flow through in the toe area. It's a stinky, messy process, but if you have low volume feet, foam liners can work wonders for you. The injected foam settles and hardens around your feet, but remains pliable and can be modified slightly after the initial injection.
Hope that helps.
Originally Posted by Ghost
The foam can be soft or as hard as you like, depending on how many extra cartridges of foam the fitter injects into your liner. Too many cartridges can bust the seams of the liner and make it a little messy though.
Let me clear up a few misconceptions about polyurethane foam injected liners:
1) The process is not "stinky" but the foam components are a
2) The process should not be "messy" with a properly prepared
liner, bootfitter, amd "bootfittee". Polyurethane foam will bleed
from the "outside" seams and can be minimized through the use
of cyanoacrylate adhesive (super glue). Internal (inside) seams
should be expected to bleed and the "bootfittee" should be
protected with the provided foot/leg shaped plastic bag. This
bag is to be placed OVER the "bootfittee's" sock.
3) The injection of polyurethane foam can only be done once.
On the other hand, liners injected with silicone, Flo, and wax/cork
mixtures can be "adjusted" by removing or adding more of the
4) The bootfitter should have on hand eye and hand protection for
himself/herself, plastic catch bags for the excess foam, hose
clamps to restrict foam flowage, paper towles, an incline
board with "pull down" handles/straps for heel retention/foam
flowability and scissors.
5) The density of the polyurethane can be adjusted by slightly
heating the catalyst to about 80F degrees.
6) Polyurethane foam does come in higher and lower density
combinations. (sometimes you will have a choice)
7) Polyurethane foam components (resin plus catalyst) has a shelf
life. If the foam is in question, don't use it.