Glass Bulb Pipette - Everythig You Need to Know

Glass Bulb Pipette is a glass laboratory instrument used for measuring and transferring a definite volume of liquid. It is also known as volumetric pipette or belly pipette. It is used where accurate measurement of liquid is required.

It has a bulb like part at the middle. This bulb holds the liquid inside it. The upper part is narrow stem and the lower part is also narrow with a tapering end.

The upper stem contains one calibration mark. This mark is used for adjusting the meniscus of liquid. It helps to take the exact volume and reduce error during measurement.

Glass bulb pipette is calibrated to deliver (TD). It means the pipette delivers its fixed volume of liquid. A small amount of liquid remains at the tip after delivery and it should not be blown out.

It is generally made up of borosilicate glass or soda-lime glass. These glasses are resistant to chemicals and heat. So, it can be used in different laboratory works.

It is mainly used in analytical chemistry and clinical diagnostic works. It is used for preparing standard solution and for accurate titration. It is not used for different volumes because it measures only one fixed volume.

History of Glass Bulb Pipettes

Glass bulb pipette has been used in analytical chemistry for more than 100 years. During this long period its design was improved many times. It was improved for getting more accurate manual measurement of liquid.

In early time, pipettes were made from ordinary soda-lime glass. Later borosilicate glass was used for making pipettes. Borosilicate 3.3 glass is more durable to chemicals, has low thermal expansion and also resist sudden heat change.
The marking system of glass bulb pipette was also improved with time. The calibration mark became more accurate and permanent. In modern pipettes, the mark is made by etching with pigment filling, fired chemical stain or enamel marking.
These marking methods help the calibration ring to remain clear for long time. It also resist removal by laboratory solvents. So, the exact volume mark can be used again and again without easy fading.

In old laboratory practice, liquid was taken into the pipette by mouth suction. This method was not safe because harmful chemicals may enter into mouth. Later mouth pipetting was stopped due to laboratory safety rules.
After this, pipetting aids were introduced. Three-valve rubber bulbs, wheeled pumps and electronic pipette controllers are used for safe suction of liquids. These devices protect the worker from contact with dangerous chemicals.
Although mechanical micropipettes and automatic instruments are now used in many laboratories, glass bulb pipette still has its own importance. It is still used for large volume preparation and for calibration of other laboratory instruments.

So, glass bulb pipette remains an important reference instrument in the laboratory. It has a simple structure but gives high accuracy in fixed volume measurement.

What are the different types of glass bulb pipettes?

The following are the different types of glass bulb pipettes-

1. One-mark bulb pipette

One-mark bulb pipette is the most common type of glass bulb pipette. It has only one graduation mark on the upper stem. It is used for total delivery of the fixed volume.
In this pipette, the liquid is filled up to the single mark. Then the liquid is allowed to drain completely through the tip. It delivers its exact nominal volume after proper draining.

2. Two-mark bulb pipette

Two-mark bulb pipette is less common type of glass bulb pipette. It has two marks on the stem. It is used for partial delivery of liquid.
In this pipette, the liquid is delivered from the upper mark to the lower mark. The volume between these two marks is measured. So, complete draining to the tip is not required.

3. Class A / AS pipette

Class A or AS pipettes are high accuracy bulb pipettes. These are used where very accurate measurement is required. They have very small error limit.
Class AS pipette is made for swift delivery. It needs a fixed waiting time, generally 5 seconds, so that the remaining liquid can drain properly. It is used in sensitive analytical works.

4. Class B pipette

Class B pipette is a general purpose bulb pipette. It has lower accuracy than Class A or AS pipette. The error limit is usually higher than Class A pipette.
It is used for ordinary laboratory work where very high precision is not required. It does not need any special waiting time after delivery.

5. Borosilicate glass pipette

Borosilicate glass pipette is made up of borosilicate glass. Borosilicate 3.3 glass is commonly used for this type. It has good resistance to chemicals and sudden temperature change.
This type of pipette is more durable in laboratory use. It is used with different chemical solutions because it does not get damaged easily.

6. Soda-lime glass pipette

Soda-lime glass pipette is made up of soda-lime glass. It is a common and economical glass material. It is used for making many general purpose bulb pipettes.
This pipette is useful for normal laboratory work. But it has lower resistance to heat and harsh chemicals than borosilicate glass pipette.

How to Use a Glass Bulb Pipette: Step-by-Step Instructions

The following are the steps for using glass bulb pipette-

Conditioning of pipette

If the pipette is clean but wet with water, then it is first rinsed with the same solution which is to be measured. A small amount of solution is taken inside the pipette. Then the pipette is rotated horizontally so that the inner wall is coated with the solution.
The liquid is then discarded. This step is repeated at least once. It helps to make the inner surface suitable for the solution.

Filling above the mark

A pipette bulb or filler is attached gently at the upper end of the pipette. The bulb is squeezed and the tip of pipette is dipped into the liquid. The pressure is slowly released so that liquid enters into the pipette.
The liquid is taken slightly above the calibration mark. It is generally taken about 5 mm above the mark. This extra liquid is needed for final adjustment of meniscus.

Sealing and wiping

The bulb is removed from the top of the pipette. The upper opening is immediately closed with index finger. It should be closed tightly so that liquid does not come down.
The outer side of the pipette tip is then wiped with clean lint-free tissue. This removes the drops of liquid attached outside the tip. Care should be taken that liquid inside the pipette is not removed.

Adjustment of meniscus

The pipette is held in vertical position. The calibration mark is kept at eye level. This is done to avoid parallax error during reading.
The pressure of index finger is released slowly. The liquid is allowed to come down until the lower part of meniscus just touches the calibration line. If any drop is hanging at the tip, it is touched with the wall of waste beaker.

Delivery of liquid

The pipette is taken to the receiving vessel. The pipette is held vertically and its tip is touched with the inner wall of the slightly tilted vessel. Then the finger is removed from the top.
The liquid is allowed to drain by gravity. It should not be forced during delivery. The liquid comes out slowly from the pipette into the receiving vessel.

Waiting and finishing

After the liquid has drained, the meniscus comes to rest in the tip. Then it is kept for about 5 seconds. This waiting time is important mainly for Class AS pipette.
After waiting, the tip is drawn upward along the inner wall of the vessel for about 10 mm. This removes any hanging liquid from the outside of tip. It also completes the delivery.

Leaving the final drop

A very small amount of liquid remains inside the tip. This drop should not be blown out. It should not be forced out by shaking or blowing.
Glass bulb pipette is calibrated to deliver (TD). So, this retained drop is already considered in calibration. Forcing it out may give wrong volume.

What are the advantages of using a glass bulb pipette?

The following are the advantages of using glass bulb pipette-

High accuracy- It is used to measure one fixed volume of liquid very accurately. It gives more accurate result than graduated pipette.

Less reading error- It has a narrow upper stem with one calibration mark. Small change in liquid level is clearly seen, so error is reduced.
Constant delivery- It delivers liquid by gravity. It gives more uniform delivery under proper laboratory condition.
Chemical resistance- Borosilicate glass pipette can resist many organic solvents, acids and bases.

Thermal resistance- It can tolerate temperature change and sterilization better than ordinary glass.
Long term stability- Glass pipette does not change its volume and shape easily after repeated use.
Fixed sizes- It is available in different fixed volumes such as 1 mL to 100 mL. So, required size can be selected according to the work.

What are the disadvantages of using a glass bulb pipette?

The following are the disadvantages of using glass bulb pipette-

Fixed volume- Glass bulb pipette is used for measuring only one fixed volume. It cannot be used for taking different volumes in the same pipette.
Need many pipettes- If different volumes are required, then separate pipettes are needed. So, more number of pipettes are required in laboratory.

Higher cost- Due to fixed volume system, many sizes are needed for different works. This can increase the total cost.
Strict technique required- Correct reading and delivery depends on proper handling. Meniscus should be adjusted at eye level and liquid should be drained by gravity.
Human error- Wrong meniscus reading, tilting of pipette or blowing out the last drop can give wrong volume. So, trained handling is needed.

Fragile nature- It is made up of glass. So, it can break easily by dropping, mishandling or sudden temperature change.
Temperature effect- It is calibrated at a fixed temperature, usually 20°C. If liquid or room temperature is too high or too low, then the measured volume may become inaccurate.
Damage by strong alkali- Strong alkaline solution can slowly etch the inner glass surface. This changes the internal volume and affects the calibration of pipette.

What safety precautions should be taken when using a glass bulb pipette?

The following are the alternatives to glass bulb pipette-

Graduated pipette- It is also called measuring pipette. It has many volume markings on a straight tube and is used to measure different volumes of liquid.
Mohr pipette- It is a type of graduated pipette. Its graduation marks stop before the tip and liquid is delivered by gravity.
Serological pipette- It is also a type of graduated pipette. Its graduation marks continue up to the tip and the last drop is usually blown out.

Micropipette- It is a mechanical piston type pipette. It is used to measure and transfer very small volume of liquid in microliter range.
Transfer pipette- It is a simple glass or plastic pipette with tapering tip. It is used for quick transfer of drops or approximate volume.
Pasteur pipette- Pasteur pipette is an uncalibrated pipette. It is used where exact measurement is not required.

Electronic pipette- It works by battery powered motor. It is used for automatic aspiration and dispensing of liquid.
Positive displacement pipette- In this pipette, piston directly touches the liquid. It is used for viscous, volatile or foaming liquids.
Plastic volumetric pipette- It is used for fixed volume measurement like glass bulb pipette. It is made up of plastic such as PMP, PP or PFA and does not break easily.

Repetitive pipette- It is also called dispenser. It takes liquid once and then delivers it in many equal portions. It is useful for repeated pipetting work.

How do you calibrate a glass bulb pipette?

The following are the steps for calibration of glass bulb pipette-

Gravimetric method- Glass bulb pipette is generally calibrated by gravimetric method. In this method, the volume delivered by pipette is calculated by weighing the liquid.

Requirements- Glass bulb pipette, distilled water or deionized water, analytical balance, receiving vessel and thermometer are required.
Temperature checking- The temperature of water is measured before calibration. Pipette is usually calibrated at 20°C. So, any change in room temperature or water temperature is noted.
Conditioning of pipette- A small amount of distilled water is taken inside the pipette. The pipette is rotated to wet the inner glass surface and then the water is discarded.

Taring of vessel- The receiving vessel is placed on analytical balance. The balance is made zero before adding the water.
Filling of pipette- The pipette is filled exactly up to the calibration mark. The lower meniscus is adjusted on the mark at eye level.
Delivery of water- The water is delivered into the receiving vessel by proper TD method. It is allowed to drain freely by gravity and the last drop in the tip is not blown out.

Weighing- The mass of delivered water is recorded from the analytical balance. This mass is used for calculation of delivered volume.
Repetition- The filling, delivery and weighing process is repeated several times. Usually 10 readings are taken for getting reliable result.
Mean mass- The average mass of water delivered is calculated from all readings. This gives the mean mass of delivered water.

Correction factor- The mean mass is multiplied with Z-factor. This factor corrects the effect of water temperature and air pressure and converts mass into true volume.
Accuracy checking- The true volume is compared with the nominal volume written on the pipette. If the error is more than acceptable limit, the pipette should not be used for accurate work.

What is the difference between a glass bulb pipette and a graduated pipette?

The following are the differences between glass bulb pipette and graduated pipette-

Volume measurement- Glass bulb pipette is used to measure and deliver only one fixed volume of liquid. Graduated pipette is used to measure and deliver different volumes of liquid.
Shape- Glass bulb pipette has a large bulb at the middle with narrow upper and lower stem. Graduated pipette has a simple straight tube like structure.
Graduation mark- Glass bulb pipette has only one calibration ring mark on its narrow stem. Graduated pipette has many graduation marks along the tube.

Accuracy- Glass bulb pipette gives more accurate and precise measurement. Graduated pipette is less accurate than glass bulb pipette.
Meniscus reading- In glass bulb pipette, the narrow stem helps to adjust meniscus more clearly. In graduated pipette, reading error is more because many marks are present.
Flexibility- Glass bulb pipette is not flexible for different volume measurement. Graduated pipette is more flexible because different volumes can be taken from same pipette.

Use- Glass bulb pipette is used for standard solution preparation and accurate titration. Graduated pipette is used for general laboratory liquid transfer and routine work.
Types- Glass bulb pipette is generally single-mark and gravity drained type. Graduated pipette has types like Mohr pipette and serological pipette.
Last drop- In glass bulb pipette, the last drop remaining in the tip is not blown out. In some graduated pipettes like serological pipette, the last drop is blown out.

Selection- Glass bulb pipette is selected when high accuracy is required. Graduated pipette is selected when different volumes are needed with less strict accuracy.

How do you clean a glass bulb pipette?

The following are the steps for cleaning glass bulb pipette-

Soaking after use- After use, the pipette is kept immediately in a tall jar or cylinder containing water or mild detergent solution. The pipette is placed tip down so that the liquid residue does not dry inside it.

Protection of tip- A small cotton pad or glass wool is kept at the bottom of the jar. It protects the narrow tip from breaking or chipping.
Cleaning of outer surface- The outside surface of the pipette is rinsed with warm water. It is gently rubbed with soft sponge, cloth or brush with mild laboratory detergent.
Cleaning of inner surface- The pipette is soaked in detergent solution for several hours or overnight. Detergent solution may also be passed through the pipette many times to remove inside contamination.

Rinsing with tap water- The pipette is washed with cool tap water. Water is passed through inside and outside until dirt and soap are removed.
Rinsing with distilled water- The pipette is then rinsed with distilled water or deionized water. It may also be soaked in distilled water for about one hour to remove minerals.
Checking of cleanliness- If the pipette is clean, water drains on the inner wall as a smooth continuous film. If water drops remain attached to the wall, grease or residue is still present.

Ethanol washing- Ethanol may be used after water washing. 70% to 95% ethanol is drawn into the pipette and then expelled out. It helps in faster drying.
Drying- The outer surface is wiped with clean lint-free cloth. The remaining drops inside are removed gently and the pipette is allowed to air dry completely.
Storage- After drying, the pipette is stored in a clean rack, drawer or canister. It should be kept dust free and safe from breaking.

Decontamination- If hazardous, infectious or biological material is used, the pipette is sterilized before reuse. Autoclave or proper chemical decontaminant is used according to the material handled.

What are some common mistakes made when using a glass bulb pipette?

The following are the common mistakes when using glass bulb pipette-

Blowing out final drop- The final small drop present in the tip should not be blown out. Glass bulb pipette is calibrated to deliver, so forcing this drop gives more volume than required.

Wrong meniscus reading- Meniscus should be read at eye level. If it is seen from above or below, parallax error occurs and wrong volume is taken.
Not conditioning the pipette- The pipette should be rinsed with the same liquid before use. If this step is skipped, water or previous liquid may dilute the sample.
Wrong delivery position- During delivery, pipette should be held vertical. The tip should touch the inner wall of the slightly tilted receiving vessel.

Air bubble formation- The tip should remain dipped inside the liquid during filling. If the tip comes above the liquid surface, air bubbles enter and volume becomes wrong.
Excess force with bulb- The pipette should not be pushed strongly into rubber bulb or filler. Too much force can break the glass and cause injury.
Mouth pipetting- Liquid should not be sucked by mouth. It is unsafe and may cause chemical exposure or infection.

Fast draining by force- The liquid should drain by gravity only. Shaking or forcing the liquid changes the delivered volume.
Touching dirty surface- The tip should not touch dirty bench or outside surface. It may contaminate the solution.
Using cracked pipette- Broken or chipped pipette should not be used. It may give inaccurate volume and may also cut the hand.

What is the difference between a glass bulb pipette and a volumetric pipette?

The following are the differences between glass bulb pipette and volumetric pipette-

Main difference- There is no difference between glass bulb pipette and volumetric pipette. Both names are used for the same laboratory instrument.
Glass bulb pipette- This name is given because the pipette has a bulb like part at the middle. This bulb holds the liquid during measurement.

Volumetric pipette- This name is given because the pipette is used to measure and deliver one exact fixed volume of liquid.
Belly pipette- It is another common name of the same pipette. This name is also based on its wide middle part or belly like shape.
Single volume pipette- It is also called single volume pipette because it measures only one specific volume. It is different from graduated pipette which can measure different volumes.

Use- All these names refer to the same pipette. It is used for accurate measurement and transfer of fixed volume of liquid.

Applications of Glass Bulb Pipettes

The following are the applications of glass bulb pipettes-

Preparation of standard solution- Glass bulb pipette is used for preparing standard solution. It helps to take exact volume of liquid for making accurate concentration.
High precision titration- It is used in volumetric analysis and titration work. It delivers fixed and accurate volume of reagent.

Calibration of instruments- It is used as a reference instrument for checking other volumetric tools. Other secondary instruments can be calibrated by using it.
Gravimetric analysis- It is used in quantitative chemistry work where exact fixed volume is needed. It helps in sensitive analytical measurement.
Large volume preparation- It is used for measuring and dispensing large fixed volume of liquid. It gives reliable volume during solution preparation.

Quantitative chemistry- It is used in chemical and biological research. It is used when one exact volume is important for getting correct result.

References

Lemon, K. (n.d.). A quick guide to classifications of laboratory glassware. Camlab.
BRAND GMBH + CO KG. (n.d.). BLAUBRAND® volumetric instruments.
Science Equip. (n.d.). Benefits of choosing borosilicate glass over soda-lime glass.

Yelimeshyn, S. (2025, December 24). Best pipette controllers & fillers: Manual, electronic & serological options compared. Boston Med Supply.
ChemScience. (n.d.). Borosilicate vs soda lime glass – Best choice for heat resistance.
Valencia College. (n.d.). Chemistry lab technique 5: Using a volumetric pipet.

BRANDTECH Scientific. (2025, October 22). Class A vs. Class B volumetrics – When to spend vs. save.
Sigma-Aldrich. (n.d.). Cleaning laboratory glassware.
Sartorius. (2024, September). Cleaning and decontamination guide for Sartorius pipettes.
Dicedpeppertsunami. (n.d.). Comprehensive guide to good pipetting technique with a volumetric (bulb) pipette? Reddit.

Simple Business Help LLC. (2021, March 16). Differences between volumetric pipettes and graduated pipettes: Pros, cons and limitations. Lab Pro Inc.
Integra Biosciences. (n.d.). Everything you need to know about the different types of pipettes.
Glassco Laboratory Equipments. (n.d.). Glassco-volumetric-glassware.pdf. Smith Scientific.
Wikipedia contributors. (2024, June 16). Graduated pipette. Wikipedia.
AHN Biotechnologie. (n.d.). How to measure accuracy and precision of a micropipette?

Sigma-Aldrich. (n.d.). How to use BRAND® pipettes.
Borosil Scientific. (n.d.). How to use the different types of pipettes.
Anamol Laboratories Pvt. Ltd. (2023, August 17). How to clean glass pipettes?
Integra Biosciences. (n.d.). Just a moment…
Zhejiang Peky Biotech Co., Ltd. (2026, January 27). Micropipettes vs. volumetric pipettes: Which is more accurate in life science laboratories? Pekybio.

Craftnexgen Infotech. (2025, August 1). Pipet vs pipette vs micropipette: Key differences explained. Uma Scientific.
Thermo Fisher Scientific. (n.d.). Pipette accuracy vs. precision.
Guinan, A. (2024, September 27). Pipette basics: An overview of pipettes and their functionality. Mason Technology.
Yelimeshyn, S. (2025, August 4). Pipette types explained: Lab uses, names & accuracy guide. Boston Med Supply.

Thermo Fisher Scientific. (n.d.). Pipette decontamination.
Keane, P. (2025, November 10). Soda lime glass vs. borosilicate glass – What’s the difference? Thomasnet.
Thomas Scientific. (n.d.). Soda lime vs. borosilicate glass in the laboratory: What scientists need to know.
The technical and metrological evolution of the glass bulb pipette: A comprehensive analysis of volumetric precision in the analytical laboratory. (n.d.).

National Institute of Standards and Technology. (2014, June). The use of volumetric pipets with NIST handbook 133, checking the net contents of packaged goods.
Luoyang Fudau Biotech Co., Ltd. (n.d.). Tips for proper pipette maintenance. FDCELL.
Riviera. (n.d.). Tolerances for graduated measuring pipettes calibrated to deliver…

University of York. (n.d.). Types of pipettes – Chemistry teaching labs.
Schurz, C. (n.d.). USP requirements for volumetric instruments. StedaLab.
DURAN. (n.d.). Volumetric glassware.
LabChoice Australia. (n.d.). Volumetric flasks in analytical chemistry: Accuracy standards explained.
DWK Life Sciences. (n.d.). Volumetric glassware.
WebAssign. (n.d.). Volumetric glassware.
BRAND GMBH + CO KG. (n.d.). Volumetric measurement.
Fisher Scientific. (n.d.). Volumetric pipets.
Heathrow Scientific. (n.d.). Volumetric pipettes.
GMP Plastic. (2025, February 20). Volumetric pipettes vs transfer pipettes.

Thomas Scientific. (n.d.). Volumetric pipettes.
Vanderbilt University. (n.d.). Volumetric and graduated glassware.
Scicluna, L. (n.d.). What are the differences between glass types commonly used for laboratory glassware? Camlab.
Cole-Parmer Blog. (n.d.). What are the different types of pipettes?
Pobel. (2024, October 3). What types of laboratory pipettes are there?

Ignacio. (2016, August 10). What’s the difference between pipettes calibrated “TD”, “TC”, “Blow-out” and related terms? Chemistry Stack Exchange.
DLAB Scientific. (2025, February 18). Why every chemist needs a serological pipette filler in their lab.
BRAND GMBH + CO KG. (n.d.). Working with volumetric instruments.

Glass Bulb Pipette – Everythig You Need to Know