Gossip meeting “Hairs and fibres”
Tuesday 7th July 2020
The COVID-19 epidemic has prevented face-to-face meetings, and this was the first Quekett meeting to be held online, an innovation that allowed members from anywhere in the world to participate. The product used was Zoom, which allows up to 100 users to participate using sound and video and to share their screens. It also allows the meeting to be recorded. Grenham Ireland and Paul Smith managed the technical side, and Chris Thomas managed the participants. Details had been e-mailed to Quekett members in advance so that they could prepare their presentations.
Quekett members can watch the video of the meeting.
David Roberts spoke on hairs and how to collect and identify them. Hair can be collected using hair tubes or from barbed wire, bird nests, fur coats, etcetera. Only the guard hairs are useful for identification, not the under fur. Hair should be washed in warm soapy water, then in distilled water, and then in 70% alcohol; a tea strainer is used to move the hairs from one bath to another to minimise loss. The cortex that surrounds the medulla contains any pigment granules, and there is an outer cuticle with scales. The scale patterns, the medulla patterns and the cross section are all useful for identification.
To illustrate his talk, David used figures from “Hair of West European Mammals: Atlas and Identification Key” by B. J. Teerink (2004, Cambridge University Press, ISBN: 978-0521545778).
To observe scale patterns, David makes a 15% gelatin solution in distilled water (with a drop of thymol as a preservative), coats a coverslip and lets it dry, then moistens it and adds hairs, leaving part of the hairs overlapping the coverslip. After the gelatin has dried, it is easy to pull the overlapping parts of the hair and peel them off. The coverslip can then be mounted on a slide.
Scale patterns on hairs [from Hair of West European Mammals]
Some hairs are quite dark, which makes it difficult to observe medulla patterns but they can be cleared with paraffin oil or hair bleach.
Types of medulla in hairs [from Hair of West European Mammals]
To observe cross sections, David fastens a hair between 2 small pieces of balsa wood and the uses a razor blade to cut a small piece that will stand up. The shape of the section can then be observed under a microscope; it is not necessary to cut a very thin section.
Cross-sections of hairs [from Hair of West European Mammals]
Another book that David recommends is “Hair and Fur Atlas of Central European Mammals” by Mária Tóth (2017, Pars Ltd, ISBN: 978-963-88339-7-6)
David informed us that fur is often sold under misleading names, and showed us the following table from a paper by L. H. Hausman (1920) in The Scientific Monthly Volume 10.
Misleading names of fur
Sable brushes are actually made from the tails of Siberian weasels.
Chris Thomas visited the Norris Museum in St Ives a few years ago and was fascinated to see 40,000 year-old mammoth hair. The curator was interested to see the hair under a microscope, and allowed Chris to take some hair home to make slides. The hair came from St Petersburg Museum and was probably from the first intact mammoth ever excavated.
Mammoth hair exhibit in Norris Museum
Chris was surprised that only a few of the hairs had a medulla, because most polar mammals have hair with a medulla to provide insulation, but research showed that the hair matched other mammoth hair samples.
Coarse mammoth hair (10× objective)
Fine mammoth hair (10× objective)
After Chris wrote a book on the subject (Marvellous Mammoths), he was contacted about a hair deposit from the Savannah River dating from the end of the last ice age that was suspected to be mammoth hair. It had similar scale pattens to mammoth hair, but SEM showed that there were distinct cavities in the medulla and so it could not be mammoth hair. With the aid of SEM by Jeremy Poole, Chris determined that it was similar to red deer, roe deer and reindeer but not to mammoth.
Cross-section of coarse mammoth hair [SEM by Jeremy Poole]
Cross-section of red deer hair [SEM by Jeremy Poole]
Scales on fine mammoth hair [SEM by Jeremy Poole]
Scales on reindeer hair [SEM by Jeremy Poole]
Joan Bingley introduced us to camel hairs. There are 2 species, the dromedary (Camelus dromedarius) from the Middle East that has short hair used mainly for industrial purposes, and the Bactrian camel (Camelus bactrianus) from Central Asia that has a downy inner coat used for luxury overcoats, rugs and knitwear as well as coarse guard hairs used for industrial purposes.
Bactrian camel hair is cheaper than cashmere, easier to dye, and the smooth hairs make it resistant to felting. The hair is shed naturally, so there is no need for shearing.
Baby camel hair [Slide by Colin Lamb]
Camel fibres [from The Microscopy of Animal Textile Fibres]
Camel fibres [from The Microscopy of Animal Textile Fibres]
Camel fibre scales [from The Microscopy of Animal Textile Fibres]
Cashmere fibre scales [from The Microscopy of Animal Textile Fibres]
Camel hair comes in a range of shades, because the animals are not all the same colour.
Camel hair brushes are usually squirrel.
Joan recommended 2 books, “The Microscopy of Animal Textile Fibres” by A. B. Wildman (1954, Wool Industries Research Association) and “Guide to the Identification of Animal Fibres” by H. M. Appleyard (1978, Wool Industries Research Association, ISBN: 978-0900820113).
Carel Sartory showed a Victorian slide of gun cotton using a Rheinberg filter with blue/red quadrants and a black patch stop, so that fibres in one direction appeared blue while those at 90 degrees appeared red, against a black background.
Slide of gun cotton, Rheinberg illumination
There are instructions on the Quekett website on Making Rheinberg illumination discs; the size of the central patch stop must be adjusted according to the NA of objective.
Most people will not have access to gun cotton, but cotton cheesecloth has a similar structure and is available from cookery shops. Carel has also observed 50 μm plankton net material.
Cotton cheesecloth, Rheinberg illumination
You do not need to make microscope slides; cheesecloth and plankton net samples can be mounted in GePe glass mounts intended for for 35mm slides. They are also good for fish scales, because they split if pressed too flat, and also for butterfly wings, which are then robust enough for children with a hand lens.
GePe slide mounts for holding fabric samples
There is a practical use for Rheinberg illumination, checking that the bonds where synthetic fibres overlap in nylon net curtains or polyester mesh are satisfactory.
Polyester mesh, Rheinberg illumination (red/green quadrants, blue patch stop)
Carel also showed a Watson slide with fibres of wood in Dr Carpenter’s test slide for achromatism.
Disc of deal – Dr Carpenter’s test for achromatism
Robert Muston showed 3 photomicrographs of a slide that he received in a PMS box, a cross-section of an elephant tail hair, and asked for help in understanding the structure of the hair. The long axis of the hair is about 1.5 mm. He wondered if it was a composite of several hairs. Crossed polarisers show bright areas around tubular vessels, but white light gave the best view. David Roberts advised that the vacuoles are probably for strength, and told us that tail hairs of Asian elephants have more vacuoles than African elephants, and they were formerly used in fly whisks. Steve Gill showed us an African elephant tail hair fly whisk and confirmed that the hairs are very coarse. Chris Thomas sent Robert a relevant paper, “Forensic species identification of elephant (Elephantidae) and giraffe (Giraffidae) tail hair using light microscopy” by Bonnie C Yates, Edgard O Espinoza & Barry W Baker, Forensic Science, Medicine, and Pathology 6, 165–171 (2010). doi: 10.1007/s12024-010-9169-6.
Elephant tail hair (white light)
Elephant tail hair (partially crossed polarisers)
Elephant tail hair (crossed polarisers and dark ground)
Alan Wood had been trying to photograph the scales on the outside of human scalp hair, and had obtained better results with transmitted than reflected light. To hold hairs tightly without dust in the background, he used a Brunel slide with a 2mm high aluminium square, and held the hairs in place with Mineral Tack.
Hairs suspended above a slide
Coarse human hair often has a medulla, which is absent in fine hair. The cortex is birefringent, and so it shows colours with crossed polarisers.
Scales on the cuticle of human grey scalp hair (20× objective, with crossed polarisers in the lower photo)
Alan also photographed one of his own brown hairs, which do not have a medulla, and was surprised that crossed polarisers did not show much colour.
Human brown scalp hair (40× objective, with crossed polarisers in the lower photo)
For a previous gossip, Alan had photographed brown human hair mounted in Canada balsam, and it showed far more colours despite being a similar diameter.
Human brown hair in Canada balsam (40× objective, with crossed polarisers in the lower photo)
Alan also showed Australian bat hairs from a Victorian slide:
Hair of Bat, Australia
Alan also showed stellate hairs of sea-buckthorn (Hippophae rhamnoides) on an arranged slide by Brian Darnton, and a stinging-nettle hair photographed on a fresh stem.
Stellate Art Work slide made by Brian Darnton (2.5× objective, crossed polarisers plus a makeshift retarder)
Stinging hair on stem of nettle (Urtica dioica) (4× objective)
These are the slides that Alan photographed:
Slides of hairs
Graham Matthews showed a cross-section of a hair of a peccary with a complex structure:
Graham also showed some peels of hairs of harvest mice (Micromys minutus) from the breeding programme at Warnham Local Nature Reserve. To make the peels, Graham paints clear nail vanish onto a slide, adds the hair, waits for the nail varnish to dry, and then peels off the hair. He has also made peels of hairs from owl pellets.
Scale patterns of harvest mouse hairs
Harvest mouse hairs under polarised light
Gordon Brown showed live images through a microscope of cactus hairs mounted in LOCA (Liquid Optical Clear Adhesive), the material featured in his article in the May 2020 issue of the Quekett Bulletin. The cactus hairs are highly birefringent.
Gordon informed us that it is possible to use multiple USB cameras and quickly switch between them in Zoom. Click the up arrow in the Stop Video icon at bottom left of the Zoom window, and you will see a list of cameras.
Switching camera in Zoom