Mineral wool with cellulose inclusions from a 2002 home  (C) Daniel FriedmanMineral Wool Building Insulation in the Microscope

  • MINERAL WOOL by MICROSCOPE - CONTENTS: microscopic examination & identification of mineral wool, slag wool also commonly referred to as rock wool used for building insulation. Photographs of mineral wool under the microscope.
  • POST a QUESTION or READ FAQs about Rock Wool mineral fiber insulation & microscopic examination or identification of mineral wool fibers

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Rock wool or mineral wool insulation examined under the light microscope.

This article describes and illustrates the microscopic properties of mineral wool or slag wool or "rock wool" insulation. Microscopic Images of mineral, stone or vitreous fibers are provided.

This mineral wool or "rock wool" insulation article series illustrates and describes mineral wool or "rock wool" and slag wool insulation materials. Rock wool or "rockwool" insulation is also called mineral wool and slag wool though there can be differences among the components of these insulations. We describe old-house or "antique" mineral wool insulation as well as modern mineral wool insulating products still used in buildings.

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Mineral Wool Insulation Under the Microscope

Mineral wool or  "rock wool" slag wool or stone wool under the microscope: Gold Bond rock wool (C) Daniel Friedman Gold bond rock wool insulation under the microscope (C) Daniel Friedman

Above, low power then high power light microscope images of Gold Bond Rock Wool insulation. The smooth surface of these fibers of this insulation are microscopically similar to fiberglass, and like fiberglass, under a forensic microscope these fibers will "disappear" under polarized light. However other fibers such as flax or cellulose, if present in the insulatin sample, will show up under polarized lighting.

Mineral wool or slag wool insulation under the microscope (C) Daniel Friedman Mineral wool or slag wool insulation under the microscope using polarized light to see other fibres (C) Daniel Friedman

Above are two photographs of the same mineral wool sample. The second photograph uses polarized light to show included fibers that are not in fact mineral wool. A closer look suggests this may be flax, similar to linen.

Below: additional microscope images of mineral wool insulation showing the broken end of an individual fiber. In the first photograph you can see a fragment protruding from the broken mineral wool insulation fiber end. This is unusual but is similar to the ends of fiberglass fibers that break with a concoidial fracture.

Mineral wool insulation fiber end (C) Daniel Friedman Mineral wool fiber end, usual case (C) Daniel Friedman

Above, our second, more gray photo shows rather more typical square-ends of fibers in a sample of mineral wool insulation. Unlike fiberglass, most of the mineral wool fiber ends we examined in this sample had square-cut ends without a concoidial fracture or fragments.

Below: a high power light microscope image of Gold Bond Rock Wool insulation showing the resin binder on crossing fibers.

Gold Bond Rock Wool insulation resin binder and fibers (C) Daniel Friedman

These enlarged slag wool / stone wool photographs were taken at roughly 1200x using Gold Bond Rock Wool insulation mounted in triacetin.

Below: glassy globules visible under low power magnification of a mineral wool fiber sample.

Glassy globules in mineral wool insulation (C) Daniel Friedman

Article Series Contents


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