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Cleaning Laboratory Glassware

How to Clean Research Lab Glassware for Microbiological Studies

Glassware for use in microbiological laboratory work should be not merely clean, but chemically clean. Test tubes, Petri dishes, flasks, etc., are the receptacles used in the microbiological laboratory for containing the different nutrient substances upon which microorganisms are to subsist.

 

Very frequently free alkali may be present on new glassware in sufficient quantity to prevent microbial growths in the nutrients contained therein. Prescott and Winslow in testing out different glassware say that, " The more soluble glassware yielded sufficient alkali to the medium to inhibit four-fifths of the bacteria present in certain cases."

Glassware which looks clean may have been used previously and should be given a thorough cleaning to rid it of possible traces of chemicals, or other substances having germicidal properties.

Follow directions carefully and clean all new and apparently clean glassware in the order given.

 

Cleaning New or Apparently Clean Glassware

All new glassware should first be treated with germicidal cleaning solutions before proceeding with the directions for cleaning glassware.

Return used cleaning solutions to the glass receptacle provided for the purpose. Do not throw it away.

Small amounts of organic matter adhering to glassware may be oxidized by these solutions, but will not disappear until removed by a suitable brush and cleaning powder. *

 

Test tubes that are not purchased sterile and reused may conveniently be placed in a large glass jar, covered with cleaning solution and allowed to stand over night. New test tubes that are sterile purchased do not need to be cleaned.

However, heavy glass jars may not stand heating in autoclave steam. New flasks may be partially filled with cleaning solution and placed in steam for fifteen minutes.

 

Cleaning Petri dishes

New Petri dishes are usually not cleaned as they are often purchased sterile.

 

Cleaning Test Tubes

New test tubes should be filled with cleaning solution, placed in a wire basket and heated for At least fifteen minutes in the autoclave with steam and pressure.

After removing test tubes from the cleaning solution:

1. Wash them in water with a test-tube brush, using cleaning powder if necessary.

2. Rinse with tap water till clean and free from cleaning powder.

3. Rinse with distilled water.

4. Drain.

5. Test tubes and other glassware, flasks, pipettes, etc., may be rinsed with alcohol to facilitate drying, then drained.

6. Autoclave if possible.

 

Cleaning Bacterial Culture Flasks

After treating flasks with cleaning solution:

1. Wash them as clean as possible with tap water and a flask brush ; use cleaning powder if necessary. (When using cleaning powder, empty all water out of the flask, wet the flask brush with tap water, dip it in the cleaning powder and then rub the soiled portions vigorously.)

2. Rinse with tap water till clear and free from cleaning powder.

3. Rinse with distilled water.

4. Drain.

5. Autoclave

 

Cleaning Petri Dishes

After removing Petri dishes from the cleaning solution:

1. Wash them in water, using cleaning powder if necessary.

2. Rinse with tap water. (It is not necessary to use alcohol or distilled water.)

3. Wipe immediately with a clean physician's cloth. Pipettes. 1. Place pipettes delivery end down, in a

glass cylinder (graduate) in cleaning solution and allow them to stand over night. (Steam may break the glass cylinder) .

2. Pipettes which have been used should be washed immediately. Grease which cannot be removed with water should be treated with 10% NaOH and then with cleaning solution.

3. Rinse with tap water, followed by distilled water.

4. Rinse with alcohol. (Alcohol may be used repeatedly.)

5. Drain.

6. Autoclave if possible

 

Fermentation Tubes Cleaning

1. Rinse with tap water/distilled water.

2. Fill with cleaning solution and heat fifteen minutes in steam or allow to stand over night if more convenient.

3. Wash thoroughly in tap water, using a test-tube brush if necessary.

4. Rinse in distilled water and drain.

5. Autoclave if possible.

 

Cleaning Cover-glasses and Slides

1. Immerse the cover-glasses

or slides, one by one in a 10% solution of sodium hydrate (NaOH) for thirty minutes only. This strength of NaOH will etch the glassware if left longer.

2. Wash separately in tap water, handling with ordinary forceps.*

3. Put, one at a time, in cleaning solution, and leave over night as convenient.

4. Wash separately in water.

5. Immerse in clean alcohol (95%).

6. Wipe with a clean physician's cloth.

7. Store in clean Esmarch and deep culture dishes respectively, to keep free from dust.

* Always handle cover-glasses and slides with forceps.

 

Cleaning Other Glassware

Some modification of these methods will be adaptable to nearly all glassware.

Note 1. Glassware containing liquefiable solid media is best cleaned by heating and pouring out the material while in liquid condition, then treating as above. (Solid media when liquefied by heat should never be thrown in the sink, as it will solidify when cold and clog up the traps and drains.)

Note 2. Flasks, test tubes, Petri dishes, etc., containing cultures, must be heated one hour in flowing steam before cleaning.

Cultures containing spores should be autoclaved previous to cleaning.

Note 3. If cultures or media have become dry, add water before heating.

Especial care must be used in cleaning glassware in which mer curic chloride or any other disinfectant has been used.