Caring and Cleaning Lab Glassware

Laboratory Glassware Cleaning Basics

If the lab glassware is cleaned immediately after use then the problems associated with dirt can be controlled to a great extent. If detergent is used for laboratory glassware washing, it should be the one that is specially designed for lab glassware cleaning. These detergents are always to be used in place of the normal dish washing detergents used in homes.

It has been seen that for cleaning lab glasswares most of the times there is no requirement of detergents or tap water. What is needed is rinsing by the appropriate solvent and a couple of rinses with distilled water. This is enough for cleaning laboratory glassware.

However removing grease while cleaning laboratory glassware is not that easy. Grease can be removed by boiling the lab glassware in a very weak solution of sodium carbonate. Alternately acetone or any other fat solvent can also be applied. Strong alkalis are not preferred and should be avoided. For removal of Silicone, grease soaking the glassware in decahydronaphthalene for at least for 2 hours is the only solution. A word of caution here- in case the lab glasswares are cleaned using hands then to prevent cuts heavy gloves should be worn. Glassware cuts are very common and can be serious. Glasswares used in the lab can be cleaned by hand washing or by using washing equipment of various types. In this section washing by hand is described.

Laboratory Glassware Hand Washing

Hand washing involves acid or base wash, rinse or soak that is performed in plastic tubs. Washing laboratory glassware by hands require suitable disposal of both acids and bases after completion of washing. Hot, soapy water also proves an effective solution for cleaning soiled lab glassware. Finally it is rinsing in purified water or tap water that normally completes the laboratory glassware cleaning procedure.

In most instances, hand-washing water reaches 120ºF maximum. This requires an autoclave for sanitization or sterilization. For drying, there are many options available. The laboratory glassware can be dried manually, hung on a drying rack or even placed in an oven. This process is quite time taking and often needs a skilled lab personnel to hand wash the glassware.

Cleaning Agents for Lab Glassware

Chromic acid is the traditional cleaning solution used for lab glassware. Chromic acid cleaning solution works best for clouded glassware or for those containing coagulated organic material. For preparation of chromic acid generally Sodium dichromate dihydrate is used. However as chromic acid is not very good for the environment their use is declining day by day. Recently other glassware cleaners which are more environment and user friendly have evolved. These days aqueous-based soaking solutions with low toxicity and ease of disposal are used for cleaning laboratory glassware. These are basically commercial formulations of chelating agents, alkalis and/or surfactants. These new cleaning agents can be used either at ambient temperature, or even temperatures up to boiling, with ventilation. These cleaning agents can take care of routine grime, all labels and numerous common chemical residues.

Cleaning of Common Lab Glassware

Some of the ways to clean popular laboratory glassware is given in this section.
Glass Joints :  Clean apparatus is an essential requirement for lab work. Grease is often used to lubricate the glass joints. The glass joints should first be wiped clean with tissue paper and then it should be removed with cotton and wool containing chloroform or ether. After it the glassware should be washed properly with detergent. Washing immediately after an experiment possibly removes organic compounds from glass apparatus. If a brush is used inside the flask, avoid scratching the glass with the metal parts. You should take every precaution to avoid scratches on the surface of glassware because these will reduce the mechanical strength of the glass joints and make it more susceptible to breakage through thermal shock. Proper cleaning and storage of glass joints significantly lengthen their life.

Here are given some important points, which should be followed while cleaning the glass joints

• Dust in glass joints may cause leakage. So all types of glass joints should be kept completely free from dirt.
• The glass joints should be kept free from grit because they may cause breakage.
• Glass joints should be wiped before use to make it free from foreign matter.
• Glass joints should be separated after use as soon as possible, preferably while still warm to prevent seizure

Slides and Cover Glass :  Nothing can be more crucial than having microscope slides and cover glass for the preparation of blood films or bacteriologic smears that are perfectly clean and scratch free. Slides should first be washed, and then placed in solution containing glacial acetic acid for around 10 minutes. Afterwards the slides and cover glass are thoroughly rinsed with distilled water and then wiped perfectly dry using paper towels or clean cloth. As soon as this is done they should be placed in a wide jar containing alcohol. Whenever the slides are needed they are to be removed from the jar and then wiped dry. In case the slides are stored dry then they should be washed with alcohol prior to use.

Burettes :  First there is a need to remove the stopcock or rubber tip of the buret. After this the burette should be washed with water and detergent. Keep on rinsing with tap water till all dirt gets removed. Then there should be rinsing with distilled water and a proper drying up. The stopcock or rubber tip should be washed separately. It is always advised to lubricate the joint with small amount of stopcock lubricant before a glass stopcock is positioned in the buret. Also the burettes need to be covered always when not in use.

Culture Tubes :  Used culture tubes need to be sterilized prior to cleaning. The most dependable technique for sterilizing culture tubes is to autoclave it for half an hour at around 121°C (15 p.s.i. pressure). As media gets solidified on cooling, it should be poured out at the time the tubes are still hot. The tubes when emptied, must be brushed with water and detergent and then rinsed with running tap water. After this it should be rinsed with distilled water, and placed properly for drying. When tubes are filled with media that is sterilized by autoclaving, there is no need to plug until the addition of the media. Thu media and tubes are both sterilized with one step autoclaving.

Pipettes :  After the pipet is used they should be placed tips down, in a cylinder or a tall jar. The cylinder or the jar should be filled with water. Care should be taken as not to abruptly drop the pipettes into the jar. This action may result in breaking or chipping away of the tips and make the pipettes useless for anything. There is a way For preventing the break up of the tips. A pad of cotton or glass wool can be placed at the jar's bottom. The water level should be sufficient to immerse the pipettes completely or at least ¾ th portion. The pipettes are then afterwards drained and subsequently placed in a cylinder or jar. The jar consist of dissolved detergent. If the pipette is exceptionally dirty, then in place of detergent, chromic acid cleaning solution is used.

After soaking overnight or for considerable time the pipettes are drained. Then under running tap water they are throughly washed till all dirt gets removed. Lastly the pipettes are soaked in distilled water for not less than 60 minutes. The pipettes are then removed, rinsed and wiped dry.

Test Tubes :  Test tubes if new should be filed up with the cleaning solution and put up in a wire basket. It should then be heated up for approximately 15 minutes in an autoclave. After removing from the autoclave they should be thoroughly rinsed using a brush under running water. Then the test tubes are also rinsed using distilled water and then drained. Sometimes alcohols are also used to facilitate drying before draining is done.

New Glassware :  Laboratory Glassware that is newly manufactured is slightly alkaline. This becomes a worrying factor in tests where high precision is required such as in trace analysis. To get rid of this problem, new glassware is first soaked for considerable hours in acid water prior to washing.