I encountered Rock Wool in my first house, a 1920's shotgun style two story with asbestos siding. I called a number of places including the EPA to find out if it was asbestos or other harmful materials. No on knew. Finally some old timer said it was made from furnace clinkers. Wickopedia seems to affirm this possibility. Note, coal slag may contain mercury, arsenic and other unpleasant substances, and wickopedia says rock wool can be absorbed into the mouth, eyes and lungs, and can be considered carcinogenic. 

"Slag wool was first made in 1840 in Wales by Edward Parry but the harmful effects on the workers caused production to be abandoned.[1] It was first produced commercially in 1871 at the Georg-Marien Hutte in Osnabruck Germany

[edit] Manufacture

"Stone wool is a furnace product of molten rock at a temperature of about 1600 °C, through which a stream of air or steam is blown. More advanced production techniques are based on spinning molten rock on high speed spinning wheels somewhat like the process used to prepare cotton candy. The final product is a mass of fine, intertwined fibres with a typical diameter of 6 to 10 micrometers. Mineral wool may contain a binder, often food grade starch, and an oil to reduce dusting.

[edit] Usage

"Though the individual fibres conduct heat very well, when pressed into rolls and sheets their ability to partition air makes them excellent heat insulators and sound absorbers. Though not immune to the effects of a sufficiently hot fire, the fire resistance of fibreglass, stone wool and ceramic fibres makes them common building materials when passive fire protection is required, being used as spray fireproofing, in stud cavities in drywall assemblies and as packing materials in firestops.

"Mineral wools are unattractive to rodents but will provide a structure for bacterial growth if allowed to become wet."

Larry2


---- Ruth Barton <[log in to unmask]> wrote: 
> Thanks folks for the answers to my question.  I still don't really know
> what this stuff is but I have about 50 bags of it in my attic, unopened.
> Dad put insulation in the attic floor in 1952 and I guess he overestimated
> the amount he needed.  I can't believe the mice have not chewed into the
> bags but they don't appear to have.  Ruth
> 
> 
> At 7:07 AM -0400 8/9/09, Gabriel Orgrease wrote:
> >[log in to unmask] wrote:
> >> What? No rodental skeletal remains?
> >cp may need to undertake invasive probes to reveal those
> >> In my house it is a natural mixture of fluffy grey stuff, mouse turds
> >> and sawdust chips.
> 
> -- 
> Ruth Barton
> [log in to unmask]
> Dummerston, VT
> 
> --
> To terminate puerile preservation prattling among pals and the
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