Workshop on making dry slides of hair, fur and feathers
Saturday 11th February 2017
Chris Thomas and Dennis Fullwood led this afternoon workshop in the PA135 Meeting Room in the Natural History Museum in London. Around 25 members attended, some of whom made long journeys such as Grenham Ireland (Dorset), Mike Asquith (Northamptonshire) and Sarah Chacko (Gloucestershire).
Chris Thomas opened the meeting by describing the various types of hair that he had brought along for us to mount, and what we could expect to see under a microscope.
Chris Thomas’s introduction
Dennis Fullwood followed with a step-by-step procedure for making dry mounts using the glass slides, card spacers, coverslips and paper covers that he had provided. He also explained how he uses punches to make the card spacers and paper covers. For dry mounts, the specimens are kept in air beneath a coverslip, not in a mountant such as Canada balsam or Euparal.
Dennis Fullwood’s introduction
Chris Thomas provided a wide selection of hairs, including alpaca, arctic hare, cheetah, sloth and even woolly mammoth.
Baby alpaca hair
Woolly mammoth hair
Peacock wing feather and silkworm cocoon
Maurice Moss brought along some corona feathers from the head of a peacock.
Peacock corona feathers
Dennis Fullwood provided specimens (including silkmoth cocoons, fur and peacock feathers) and materials (slides, card spacers, coverslips, paper covers, labels, PVA adhesive, brushes and holders for taking slides home). To save time, Dennis brought a lot of 3″×1″ slides to which he had glued black card (250–280 gsm) spacers.
Materials and specimens
Dennis demonstrated different types of punch for making the circular holes in the spacers and covers. Sets are available cheaply on eBay, and Dennis showed us how to use them with an arbor press.
Cheap punch set
This Boehm set is expensive but is well made; Spike Walker uses these punches for making his coloured + polarising stops for Spikeberg illumination.
Boehm punch set
Individual leather punches are available in 1mm steps (the sets usually only provide 2mm steps) and are inexpensive. You need to hit them with a heavy hammer (Dennis uses a 4 lb one) so this method is noisy.
Leather punch and 4-pound hammer
Using the slides with black card spacers, members were able to select hairs (or use their own), fur and feathers, cut them to fit within the circle, and paint PVA adhesive onto the top of the spacers.
Dennis recommended brushes from Rosemary & Co, specifically their Series 301 Size 2 for applying PVA and for ringing; they are better than the ones used at the workshop. The PVA adhesive should be the craft version, because the woodworking version is acidic and can damage the card and paper.
Applying PVA adhesive
The next stage was to gently lower a coverslip (very thin glass, about 0.17 mm) onto the adhesive. Some people noticed that the coverslips were not clean, even though they were new. Dennis explained that even the very expensive coverslips that the Museum buys are not really clean; he uses a mixture of alcohol and water with a tiny drop of washing-up liquid for cleaning coverslips.
Applying a coverslip
Slides should be labelled with Indian ink, or with a pen that contains pigment ink that will not fade. Do not use an ordinary ball-point pen. Dennis provided sheets of labels for us to cut out and use, for adding details of the mounter and the specimen. We used PVA to fasten the labels to the slides.
Pigment pen (0.05 mm)
The finishing touch was to use PVA to attach a black paper cover (100 gsm, with a circular aperture) on top of the coverslip, to hide the adhesive.
Dennis provided a large hotplate set at 70°C for drying the adhesive, and heavy metal nuts to hold the coverslips and paper covers in place.
Drying slides on a hotplate
Members made some notes to remind them of the procedures, and prepared some really neat slides.
Slides and notes
After preparing slides, we were able to examine them using some of the Club’s stereo and compound microscopes.
Peacock corona feather
For a cheap source of polarising material, Chris recommended 3D glasses as used for viewing 3D movies. The glasses are available cheaply, and the material can easily be removed. One piece goes between the light and the specimen, the other goes somewhere above the specimen. Rotate one piece to obtain the maximum extinction.
3D glasses (for polarisers)
One of the Club’s Zeiss Standard microscopes was set up with a camera to display images on a television, so we could all see the colours in hair viewed with polarisers.
Hairs on the television
Brown human hair
Brown human hair (crossed polarisers)
Both ends and a middle section of a polar bear hair. As the hairs were shed rather than being pulled out, there is no root. The central medulla is composed of air-filled cells that refract light to give the white colour and also provide good insulation. [by Pam H.]
This paper provides a lot of information about colouration in animal hair:
- Hausman, L. A. (1921), Hair Coloration in Animals, The Scientific Monthly, volume 12, pp. 215-222
John Gregory with a modern Chinese microscope
Mark Shephard with a Russian Lomo microscope
Mike Asquith with Dennis’s Nikon Labophot microscope
Sarah Chacko with a Carl Zeiss Jena microscope
Pam H. brought some notes on using clear glass glue from Wilko as a mountant, with photographs of some slides that she has made.
Wilko crystal clear glass glue
Pam also brought some items that used to belong to Jamie Nelson to give away, including small slide boxes, graph paper, chemicals, and Cargille refractive index reference liquids.
Report and photographs by Alan Wood