from NorthFurFX.com:
What is the difference between 'Hot Foam', 'Cold Foam', 'Slush/Slip' cast latex?
Slush or slip cast latex is liquid latex that is poured into our moulds and through a build-up of layers create the prosthetics or masks. The result is a hollow latex shell. In the case of prosthetics, they have thin edges, while masks will have thicker edges. These hollow shells are glued to your face only around the edges. They are best suited for use for background characters, or anyone with few lines. They are tough and durable, lasting a dozen or more applications and usually don’t need a remover since they can be peeled off like band-aids. They are flexible and will move with the mouth and some expressions, but they aren’t as flexible or as expressive as hot foam latex. Since they are hollow, if they’re improperly applied, they can muffle the voice and make it sound nasal due to echoing.
Hot foam latex is a foam latex that is whipped up, poured into our moulds, assembled with a face core and then placed in an oven to bake for a few hours. The result is a soft filled foam piece. They have thin edges and can be glued down completely to your face since it comes into more contact with more surface area than just the edges. These are best suited for main characters or for anyone with a lot of signing and lines. Since they are filled, there will be no problems with echoing. Foam latex is extremely flexible and expressive and will give the liveliest performance. However, foam latex is more fragile and can tear, so it requires a remover to remove the pieces. They have a lifespan of about 10-12 applications.
Cold foam latex is an expanding polyurethane foam (A-B Foam) that is sandwiched between slush cast latex layers. The result is a filled foam piece with thick edges. This type of material is best suited for mask making, props and anything that needs to be static as it’s the least flexible of all materials we use. It’s the best basis for making costume heads that are furred since it can be flexible, yet solid enough to hold its shape. It’s also durable with the slush/slip cast latex skin, masks made with cold foam could last for 5 years or more. It’s not suitable for being glued on like a prosthetic.
I don't have experience with it yet, but I am ordering a cold foam wolf muzzle from them.