Updated 2017: We no longer use smoothie on any of our full wetsuits.
What is smoothie?
'Smoothie' has become a common way to describe single-sided nylon neoprene. This is neoprene with a nylon (fabric) finish on one side and a rubber finish (smoothie) on the other.
Where is it used?
Smoothie is commonly used in the center chest panel and center back panel. It was originally used in these panels to lower the wind chill factor, as after immersion in water the smoothie drained away any water particles. Because the smoothie did not hold water the wind chill factor against the chest was much lower. As opposed to cheaper nylon neoprenes in the chest panels that hold the water particles so when the wind hits it, there is a cooling effect.
There are different types of neoprene in existence. The original type of neoprene (first invented in 1931) is made from a petroleum base and is known as petrochemical neoprene, this is what alot of big brands use still. Because the main ingredient of this neoprene is a liquid it is heavy and absorbs water like a sponge. In fact it has a cell penetration count of 64%—making it even heavier during and after use.
The neoprene we use at Seventhwave—was invented by Yamamoto Corporation (c.1964) and is made from calcium derived from pure Limestone. Limestone neoprene has nitrogen cells with a cell penetration count of 94%, making it much lighter in weight and less absorbent. In other words, it is more water repellent than petrochemical neoprene.
Because the Yamamoto Limestone neoprene does not absorb any water, we have found that our nylon/nylon neoprene is actually warmer that petrochemical neoprene with a smoothie finish. It is also far more durable.
Smoothie is considerably cheaper than nylon neoprene and the construction is alot faster which is why large manufactures prefer to use smoothie.
Why we don't use smoothskin:
Smoothie can rip easily and is usually the first panel on a wetsuit to deteriorate over time. Repeated rubbing on the same spot ie from ribs or deck grip, against a board causes the smoothie to wear thin. This is because smoothie is not as strong as neoprene with nylon on both sides (nylon/nylon)—the strength of neoprene is in the nylon and not the rubber. For the same reason smoothie is not as strong around seams, and is very susceptible to sharp objects, especially fingernails. This means you have to be extra careful when you grip it.
You can only glue it in and are often the first panels to come apart. By not using smoothie, we can ensure all of our seams are well constructed, which obviously increases the longevity of the wetsuit immensely.
Basically, we don't use Smoothie in our wetsuits as you get a much longer life from your wetsuit and it will be just as warm (or warmer) if it's made from Yamamoto Limestone neoprene.