Rockwool® is sort of like cotton candy made out of rocks. It is processed from leftover mineral slag created as a by-product of ore refining. The slag is dumped into a heated spinner and, just like with cotton candy, is spun into thin fibers as it melts and spins. Then it is packed into bales and shipped. The process is imperfect, however, and the fibers usually have a small bead of solid mineral on the end. When used in a slurry, these beads break off in the water tanks and collect in the bottom as a fine sand. They must be cleaned out periodically or they will interfere with the operation of agitators and pumps.

Rockwool® is used in manufacturing because it is non-flammable, resistant to many chemicals, and its fibers can hold a finished product together in much the same way as wood fiber does. It has many of the benefits of asbestos, but is much safer.

Many people compare asbestos to Rockwool® because they are both mineral fiber, but Rockwool® is not asbestos. Asbestos, when friable, floats in the air for a very long time; Rockwool® does not. Asbestos has points and barbs that stick in your lungs; Rockwool® does not. Asbestos can never be broken down by your body's immune system, once it's in your lungs, it's there forever. Rockwool® can be broken down and absorbed.

Rockwool® can irritate and cause a red, itchy, persistent rash if the fibers become embedded in the skin. Once in the skin, they are difficult to see and remove. Washing will get rid of most of them, but you'll probably be itchy for a couple of days before your body can deal with the rest of it. To prevent irritation, you should wear a long sleeved shirt and gloves when handling Rockwool®, and if you want to be cautious a dust mask couldn't hurt.

I have been informed by liveforever that Rockwool® is a brand name that has entered the common usage, like Kleenex®, Xerox®, and Sheetrock®. Rockwool International's official web site is located at and contains a brief history of the company and its products.

    Acceptable generic terms for this product are:
  • Slag wool
  • Stone wool
  • Mineral wool
  • Mineral fiber
  • Man-made mineral fiber
  • Man-made vitreous fiber
  • Synthetic vitreous fiber

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