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Mouting aquatic hyphomycetes using PVA

A guide for making (semi-)permanent slides

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Peter Braubach 2026-04-26

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Aims

Problem: Slides prepared from fixed foam samples tend to dry up fast.

A mounting medium can prolong slide life.

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Preparation of the PVA mounting medium*

! Observe lab safety and precautions, you are handeling acids !

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  1. Dissolve 2g of polyvinyl alcohol (PVA) in 10-15 ml hot distilled water.
  2. Add 5ml concentrated lactic acid and 5ml glycerin to the warm solution.
  3. Optionally add dyes (Cotton blue**)

The resulting mixture has a honey like consistency.

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*translated from Schumm, F. Polyvinylalkohol als Einschlussmittel für Dauerpräparate, Mitteilungen der Mikro AG Stuttgart e. V., Heft 8, 1989 (https://www.tmg-tuebingen.de/wp-content/uploads/2022/08/Polyvinylalkohol-als-Einschlussmittel-Dr.-F.-Schumm.pdf)

**concentration depends on the concentration of the cotton blue solution, can also be added to the prepared PVA solution

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Polyvinyl alcohol PVA

  • Polyvinyl alcohol (PVA) is a synthetic polymer, non-toxic �� used in biocompatible hydrogels which have been used for a variety of applications such as vascular stents, cartilages, contact lenses (Wikipedia)

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🡪 Water soluble embroidery backing

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  • Is not Polyvinyl acetate (White glue/ Wood glue)�

Sorry Art Attack!��

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Mouting procedure

  • Add a drop of sample
  • (Spread it on the slide)
  • Let it dry
  • Air dry or �dry or on a hot plate
  • Add a drop of mouting medium
  • Lower a coverglass from the side and press
  • Keep some amount of excess – the medium shrinks considerably when drying
  • You can repeat steps 1 and 2 to concentrate samples

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Demo video

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Benefits

  • Samples
    • can be prepared as batch
    • can be observed multiple times over days (and weeks)
    • stop moving (after some time)
    • are flattend (after some time)

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  • Stain can be included

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  • Contrast methods (DIC, phase contrast) still work.

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Alternatives

Lactophenol Cotton Blue (LCB) is commonly used in mycology.

- Prolongs slide life

- Fixes sample

- Does not solidify

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Hydromatrix (LM-Scope)� https://www.lmscope.com/de/HYDRO_MATRIX.html

not tested, expensive

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Seal with nail varnish (suggestion by Magnus)

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Other mounting mediums for aqueous media (Malinol, Incudal A), not tested.