In "The World of the Microscope," Oxlade and Stockley explain that stains help differentiate parts of organisms, such as cell walls and nuclei, by increasing contrast and detail. Transparent organisms such as bacteria and plankton may be easily seen under a microscope when they or their backgrounds are stained. Several inexpensive, readily available household chemicals can be effectively used as amateur microscopy stains for plant and animal tissues, blood, fungi, and microbes. In "Some Stains for Amateur Microscopy," Walling finds that slides created using simple semipermanent mounts and noncommercial stains may last for years.
- Skill level:
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Things you need
- Glass slides
- Food colouring
- White vinegar (5 per cent acetic acid)
- Rubbing alcohol
- Red and blue ink
- Blotting paper or paper towels
- Methylene blue
- Gentian violet
- Watercolour paints
- Boiled red cabbage, or red or yellow onion skins
- Sodium hydroxide
- Candle and matches
- Utility knife
- Clear fingernail polish
- Small paintbrush
- 10 mg (1/2 lb) weight
Dilute one drop red or blue food colouring in 29.6ml (1 oz) water. For greater detail and contrast, mix one or two drops each of red and blue food colouring, five drops water, two to three drops white vinegar, and three to five drops rubbing alcohol. Follow step 1 in the Simple staining procedure detailed below. Change stain colour, intensity or pH by varying the number of drops of vinegar or food colouring.
Apply one drop blue ink to sample or touch blue pen tip to sample edge. Add coverslip. After four minutes, apply red ink drop or touch red pen tip to coverslip edge. Allow ink to absorb. Blot. Examine under microscope.
Place sample in water drop on clean slide. Place coverslip on edge beside sample, lower diagonally. Blot excess liquid. Tap gently with pencil to remove air bubbles. Wet mounting allows study of live specimens most stains kill.
Using tweezers or eyedropper, place sample in water drop on clean slide. Smear by dragging another slide held at 45 degrees lengthwise across sample. Holding smear high over candle flame, gradually evaporate water. Avoid boiling, which destroys samples. When dry, "fix" smear to slide by passing slide rapidly through flame four times. Once slide cools, add one or two drops stain. Wait five minutes to an hour. Optimal staining times and amounts vary based on stain and sample type. Wash stain off slide with slow-running water. Carefully blot dry. Rubbing destroys samples. Cover with coverslip. Examine under microscope.
Dip larger tissue samples in small bowl of stain for three minutes. Rinse by dipping quickly in water. Wet mount stained sample.
"Pull" delicate wet-mounted samples by applying a drop of stain to slide beside coverslip. Place blotting paper against opposite coverslip edge. Stain will pull under coverslip through specimen, with blotting paper absorbing excess liquid. Repeat process on same slide using different coloured stains to produce multicoloured specimens.
Use glycerine and gelatin for semipermanent mounting. Place 10 g (8 oz) gelatin, 25ml (1 oz) water and 25ml (1 oz) glycerine into jar and immerse in hot water until gelatin melts. Place one or two drops warm, melted gelatin onto stained specimen. Cover with coverslip. After gelatin sets, cut excess from around coverslip edges with utility knife. Seal your slide by painting one or two coats of clear fingernail polish over coverslip with a small paintbrush, overlapping coverslip edges approximately 1mm (1/32 inch). Apply a flat 10 mg (1/2 lb) weight, such as a hardcover book, to your slide overnight.
Tips and warnings
- Slow wet-mount evaporation by adding a drop of 10 per cent glycerine or rubbing petroleum jelly around coverslip edges.
- View unstained wet mounts using top lighting and stained slides using bottom lighting.
- Staining solutions: methylene blue for aquariums red eosin (sold as a disinfectant), iodine from first-aid kits, gentian violet (a yeast infection remedy), watercolour paints, boiled red cabbage, red or yellow onion skins, ammonia and sodium hydroxide.
- Many chemicals are toxic or irritating if inhaled or exposed to skin. Wash your hands thoroughly after handling any chemical.
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