Photograph of preparation of a microscope slide using Cargille's Meltmount. Microscope slide preparation method
How to prepare slides of mold pollen bioaerosols - for indoor air quality analysis,Mold Testing Laboratory SOP

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Aerobiolgy & forensic microscopy lab procedures: how to prepare microscope slides for lab analysis. This is a collection of aerobiology and mold testing lab standard operating procedures - SOP's and slide preparation recipes useful for identification of mold, pollen, animal dander, skin cells, mite fecals, mouse dander, and other airborne allergens and bioaerosols. Comments and suggestions are invited.


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Slide Preparation Procedures & Guidelines

Air sampling cassette slide preparation (C) Daniel Friedman

Our photo (left) shows particle traces from two different air sampling cassettes prepared on microscope slides for further evaluation.

Our study comparing the performance of these cassettes is found at AIR TEST SAMPLING CASSETTE STUDY.

Article Series Contents:

Microscope Slide Stain and Media Recipes

How to Prepare Permanent Microscope Slide Mounts

Particle trace from an air plenum (C) Daniel Friedman Here is a list of some candidates. WARNING: some of these involve dangerous chemicals, possibly carcinogenic (cancer-causing) and should be used only with expert advice..

  • Canada Balsam - traditional, excellent slide mounting media, generally not available. See Cargille's "Meltmount" alternative.
  • Clear nail polish - experimental -DF
  • Damar Varnish - see Brinkworth and Smith article below
  • Fructose Larry Legg's recipe
  • Glycerin or glycerine jelly. DF note: we've been disappointed that even after adding phenol or other preservatives some of our glycerine jelly slides become cloudy or even opaque with age. We no longer recommend this mountant for permanent slide mounts.
  • Gum Arabic (Acacia) or similar water soluble gums
  • Hyrax / Dirax high refractive index mountants - Northern Biological Supplies
  • Lactic acid combined with phenol (carbolic acid), polyvinyl alcohol, glycerine, water. (Not for caliciferous materials - you'll find that materials like drywall dust, gypsum, some plaster contents, will dissolve and then recrystalize in this media)
  • Loctite glass bond - local auto supply stores, needs UV light to cure - experimental, Brinkworth and Smith [DF note: We have had good results using this slide preparation media for permanent mounts of certain particles; we need to research the refractive index but in general that's not been a problem with paint samples nor with fungal spores or other common indoor building dust particles. We use a halogen lamp to generate the UV needed to cure the mountant.
  • Meltmount - see below
  • Mowiol - available from Burkard as a replacement for Gelvatol - data to be added below
  • NBS Bioseal Two
  • Numount - from Brunel microscopes & Northern Biological Supplies
  • Turtox - no longer available, formula sought. See Howey's article
  • Water soluble gums - gum Arabic (Acacia)

How to Use Gelvatol to Prepare Microscope Slides - A Detailed Step by Step Procedure

Recipe for Gelvatol Slide Mount Medium

Gelvatol may be used as a permanent slide mounting medium for mold spore or pollen slides. Gelvatol has been replaced by Mowiol from Burkard - see Mowiol below.

  • 100 ml H2O (I would use distilled water)
  • 35g Gelvatol (or Mowiol from Burkard)
  • Polyvinyl alcohol (from Fisher Scientific, or other sources)

Heat to dissolve, not to much. Then add:

  • 50 ml Glycerine (Glycerol, Fisher Cat. No. ?)
  • 2g Phenol (as a preservative if needed)(Phenol smells a lot and it is no good for health, it gets yellow with time, I do not use it)


  • ACID fuchsin (as a colorant for SPORES if needed - Fisher Cat. No. AC22790-0250) Just use a few crystals, mix and wait. Add more if wanted, do not use too much as it will hide the structures.

OR BASIC fuchsin (as a colorant for POLLEN if needed - Fisher Cat. No. NC9653986)

OR no colorant

Keep closed tight because it gets harder as it gets in contact with air.

Source: Burkard company; I was told that they call the "polyvinyl alcohol" Gelvatol, available from Burkard.

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