Roger,
Do you remember this discussion about Brown Sugar at class? What is brown sugar?
A lot of people instead of using Turbinado, just dehydrate their brown sugar. It's the moisture in the BS that is caking up your rubs.
GeiyserQ..You asked about Turbinado, here's what I know:
Cooks Thesaurus for Sugar Another source's definition of Turbinado. People sometimes call it "coffee sugar" because of the crystal size. Think of it like this. As kosher salt is to table salt, turbinado is to brown sugar. Both are just bigger crystals -- basically, at least for our discussions.
or
Turbinado sugar is a healthier alternative to refined sugar. While both sweeteners are made from sugar cane, turbinado sugar does not undergo the same degree of processing that refined sugar does. It retains some of the natural molasses and so is tan in color. Liquids are spun out of the sugar thus the name "turbinado". Unlike refined sugar, turbinado sugar retain more of the nutrients found in sugar cane.
or
Turbinado Sugar is large crystals of light (or dark) brown sugar are prepared from the unrefined, minimally processed, juice of sugar cane. The juice is spun out of the cane, thus the name Turbinado.
And finally, according to Sugar facts at Sugar Order Sugar facts Everyone knows that many companies make brown sugar by just adding molasses to white sugar. Well, turbinado can be created the same way.
Those are the only way, but a lot of companies make them that way.
See, now you know...
or course I didn't mention "Succanat" which is "Sugar Cane Natural" which is a different taste also.