Frequently Asked Questions (FAQs)

Most of our glass items are made by hand. This enables us to easily customize items in small batches if required.

Some examples of common required custom modifications are:

Nonstandard volumes or graduation lines:  for example a 21.8ml bulb pipette

Nonstandard colours for better visibility: We keep white, blue, black, green, yellow and red inks in stock, and can obtain other custom colours on request.

Colour Patches for labelling. We also apply permanent colour patches to items without the risk of accidental detachment. These patches use the same permanent inks as all our glassware and can be autoclaved and washed multiple times in an industrial dishwasher without fear of contamination or loss.

Calibrated necks on flask to allow for a range of readings.

Variations in neck sizes to allow for more accurate readings.

Items can be calibrated to contain a volume or deliver a volume in a set time.

Yes, see the FAQ’s at the end of this page and our amberising service page.

Yes, contact our glassware repair service

Yes, contact us with the type and/or functionality of the glass required, and we will tell you whether we can help.

Yes, see the FAQ’s at the end of this page and our plastic coating service page.

Scientific glassware is used in laboratories for various purposes such as measuring, mixing, heating, cooling, distilling, and storing chemicals and solutions.

Volumetric glassware is used for measuring liquids. The commonest types are measuring cylinders, volumetric flasks, burettes, bulb pipettes, and measuring pipettes. These pages also contain a general usage guide. More unusual ones can be found here. Graduated glassware, like standard beakers and Erlenmeyer flasks are not considered volumetric glassware even though they usually have a nominal volume scale on the side. This is because they are not measured or checked to be accurate and should not be used even for qualitative measurements.

Yes. Plastics (for example polypropylene and PTFE) are used when breakage risk or certain chemical compatibilities are an issue. However, they may not tolerate heat or solvents as well as glass. They also tend to be easier to scratch and more difficult to clean.

Volumetric glassware (like volumetric flasks and pipettes) is designed for precise single measurements for quantitative work. Graduated glassware which show a nominal volume allow for approximate volume estimation for qualitative work.

Jointed glassware features precisely machined connectors that fit together with other glass components. They are used for many basic reaction processes such as refluxing and distillation. Grease may be required for airtight seals.

It depends on what they are being used for. For distillation and refluxing they are best avoided as they can contaminate the sample. For vacuum work they are needed as the ungreased joints may leak air slowly, or jam together under the vacuum.

See our webpage on the use of volumetric flasks.

20°C All volumetric glass items in the UK are calibrated for use at 20°C and should be used as close to this temperature as possible.

27°C - Some volumetric items manufactured for use in warm climates are calibrated to this temperature instead of the more usual 20°C. The reference temperature should be clearly stated on the glassware.

It is always preferable to agitate a solution by inverting the flask several times, then making it up to the mark, rather than attempting to stir it mechanically. If it is required, then use a PTFE coated stirrer rather than a glass rod that might damage the inside of the flask.

No. All our items are calibrated using distilled water at a standard temperature of 20C. Other solvents have different densities, surface tension and viscosity which may affect the volume. We therefore do not recommend measuring non aqueous solvents in volumetric glassware for anything other than qualitative work.

Borosilicate glass is highly resistant to thermal shock, chemical corrosion, and mechanical stress, making it ideal for laboratory applications. It is also lightweight and has a low refractive index, improving handling and visibility of the contents.

Volumetric glassware can be made of borosilicate or soda glass, but the latter is increasingly rare, as borosilicate glass has better characteristics for laboratory work. It is harder, less likely to chip or crack, lighter, stronger, more chemically resistant and harder wearing than soda glass.

Each item in our catalogue and website has the type of glass used in its construction in the notes after the title name. There are three types of glass that we use in our standard products.

Borosilicate glass

Most of our glassware is made of borosilicate glass, type 3, the same type of glass as the brand name Pyrex. This type of glass is lighter, tougher, and withstands thermal shock better than soda glass. It also chips less easily. In practical terms this means that you can pour boiling water into a borosilicate glass container and it will not crack. Most volumetric glassware is made of this material.

Soda Glass

This is “ordinary” glass, with a similar basic formula to that used in bottles, jars and drinking glasses. It is still used for some basic volumetric glassware like measuring pipettes. We use type 3 soda glass in our factory.

Neutral Glass

This is a “halfway house” with properties between those of soda glass and borosilicate glass. It is usually used for consumable items such as bottle droppers and not for volumetric glassware.

Specialty Glasses

There are many different types of glass developed for specific applications. For example, glasses with a specific expansion coefficient suitable to bonding to sapphire windows, or amberised glasses to protect the contents from light.

Avoid strong exothermic reactions, high-pressure reactions, and reactions involving hydrofluoric acid or alkali metals in standard glassware. Specialized containers or materials may be required.

Generally, glass is very chemically stable, but it is susceptible to slow attack from strong alkalis, and rapid attack by some fluorine containing compounds.

Exposure of volumetric glassware to strongly alkaline solutions like NaOH and KOH, or cleaning fluids such as Decon should be minimised to maximise the life of the glassware. Alkaline solutions should be decanted out of the glassware after being prepared and cleaning fluids should be used for an hour or two. The glassware should not be left in cleaning fluid overnight. If the alkali does attack the surface it will become cloudy and the volumetric item should then be discarded as its accuracy may be compromised.

Solutions containing fluoride or HF should never be used in volumetric glassware as they will attack the surface of the glass, compromise the accuracy of the glassware, and will contaminate the solution with silicates. In this case use of a plastic volumetric equivalent is indicated.

Borosilicate glass is microwave safe. Metal parts should be removed before placing the item in the microwave. Generally plastic parts used in scientific equipment for connectors or adaptors are made of polypropylene or PTFE which are also microwave safe. Make sure they are not forming an airtight vessel as the rise in temperature will increase the internal pressure, with the risk of explosion. Overtight plastic screw threads may also crack with high temperature.

Borosilicate beakers can be used on a hot plate, but with care. Do not place a cold beaker on a preheated hot plate as the thermal shock may break it. Consider using a silicone bath, or other more indirect method of heating.

Borosilicate glass can be heated with a flame by an experienced operator by starting with a soft flame gradually applied, and increasing the heat slowly. This is not something that should be attempted without experience and guidance as it is very easy to crack the glass. The thicker the glass the harder and slower this process is. Naked flames are best avoided in labs in any case as they present multiple hazards. Burns, gas explosions, igniting of solvents and violent glass cracking are some of them. Also heating liquids with flames can cause the liquid to “bump” due to superheating, and can easily throw the liquid out of the glass container at speed and without warning.

Fritted glass filters are porous glass discs used for filtration and gas dispersion. They must be cleaned thoroughly and are fragile: avoid poking or scraping them.

Yes. Amber glassware protects light-sensitive chemicals (like silver nitrate or some vitamins) from UV degradation. Use it when storing or working with such substances.

Glassware should be rinsed immediately after use. Use appropriate detergents, solvents, or acid baths depending on the residue. Rinse thoroughly with distilled water.

Yes, our glassware is dishwasher safe, and the graduations will not come off, even after repeated washings.

First try

• Soaking in detergent
• Using brushes designed for lab glassware
• Putting in an appropriate laboratory glass washer
• Using decanter cleaning balls

If these methods don’t work there are more hazardous and stronger methods:

• Using appropriate organic solvents.
• Use a base bath (with caution and proper PPE)
• Applying chromic acid (with caution and proper PPE)

These methods should only be used by trained operatives, as there are multiple serious hazards to be aware of. For example Chromic acid can produce carcinogenic compounds, and strong bases can blind on contact with eyes.

Residual moisture can dilute solutions, interfere with chemical reactions, or cause dangerous splattering, especially with water-reactive substances. It also affects the volumetric accuracy.

Rinse with distilled water—if water forms a continuous film without beading or spots, it’s probably clean. Small quantities of grease or other residues on the glass will cause the meniscus to break up into droplets on the surface.

Inspect before each use for cracks, chips, or stress marks, especially if used under vacuum or heat. Holding an item up to the light and looking for any issues before use can prevent accidents, and is quick and easy to do.

Tap water may contain impurities, both mineral and trace organic. Always finish rinsing with deionized or distilled water, especially before analytical or quantitative work.

Yes, pipetting by mouth is strictly forbidden in all labs, even if you think the solution is safe.

No. Damaged glassware is structurally compromised and may break during use, posing a safety risk.

Yes, most borosilicate glassware can be autoclaved. However, lids or plastic parts attached to glassware may not be suitable for high heat.

Only glassware rated and designed for vacuum or pressure use should be used. Always inspect glassware before applying positive or negative pressure. Items with thin walls, flat bottoms, or cracked, chipped or severely scratched should not be put under pressure. Pressure should be applied or reduced gradually. Use appropriate shielding like a safety screen or protective cage. Other precautions can be taken such as nets or plastic coating on the glass to reduce the amount of flying glass. We can undertake plastic coating of most items if required. See our plastic coating service page.

Most glassware is not designed to work under pressure but can be made to do so if needed. There are no safe rules of thumb, so please ask us if you want to design something specifically.

Positive Pressure

Glass apparatus should not be put under any positive pressure unless it is specifically designed to withstand a designated pressure. Even a relatively low positive pressure will cause ground glass joints to blow out with dangerous force, and moderate pressure could cause a vessel to explode. Please send us an enquiry if you require an item for use under positive pressure stating the pressure it must withstand.

Negative Pressure – Vacuum glassware

Standard volumetric glassware is not designed to work under negative pressure. However, we can adapt most items to work under these conditions. Please send us an enquiry for items of this type.

This is usually due to thermal shock—rapid temperature changes cause stress in the glass, especially if it has defects or uneven heating. Borosilicate has better resistance to most other glasses, but it is good practice to use a slow and even heat source like an autoclave or silicone bath, rather than flames or hot plates if possible.

Stop all activity immediately. Use forceps or a brush and dustpan to collect glass shards—never use your hands. Make sure you dispose of glassware in a clearly labelled puncture resistant designated glass disposal bin. Shards of glass will go right through a plastic bag and can be a hazard to anyone picking it up. Do not dispose of borosilicate glass into a glass recycling or bottle bank scheme. Borosilicate glass has a higher melting temperature than domestic soda glass and may render the whole batch unusable.

Use heat-resistant gloves or tongs. Remember, hot glass looks the same as room-temperature glass, so treat all recently heated items with caution.

100°C – At this temperature and above soda glass becomes vulnerable to thermal shock, if the glass temperature is changed rapidly. Placing hot glass on a cold surface or pouring boiling water into cold glass can cause it to crack. Always heat and cool glass items slowly.

160°C - All glass types can be safely dried in a drying oven at up to 160°C. They won’t crack in the oven but may do so when placed in the oven or removed from it due to thermal shock.  Avoid placing items directly onto a hot metal surface in the oven otherwise they may crack. A fine metal wire rack in the oven will be safe for borosilicate items. Similarly, when removing them from the oven, avoid placing them on a cold metal surface. A wooden surface should be safe for both borosilicate and soda glass, but may scorch the wood a little, and will damage polished wood. Items with ground glass joints should be disassembled before placing in the oven to avoid jamming or cracking of the joint.

300°C - Avoid subjecting volumetric glass items to repeated cycles of heating and cooling over 300°C as this could affect the volume, even though it is well below the melting point of the glass.

500°C – Volumetric glassware should not be exposed to these temperatures as the volume may change significantly, even though it may look unaffected. This is the maximum temperature that any borosilicate glass item should be subjected to and then only for a short period of no longer than a few minutes. At this temperature borosilicate glass is very susceptible to thermal shock, even from a cold draft. Soda glass will melt before reaching this temperature.

Naked flames like Bunsen burners should never be used with volumetric glassware.

Ensure you are using the right size. Do not use excessive force when fitting the bung into the neck of a flask.

This operation must always be done with care, as excessive force can result in the glass olive breaking with a high risk of giving the operator a very unpleasant incised wound. Ensure the tubing is of the correct size. Warm the end of the rubber tubing gently and use a thin film of silicone oil on the olive. If oil is not available or inappropriate, wet the tube by dipping it in water. If this is done correctly minimal force is needed to fit the tube onto the olive. When removing the tubing from the olive warming will also help. If the tube has become firmly stuck it is safer to cut it off rather than pulling hard.

Always support the glassware from underneath and do not lift by the neck or rim alone.

Sometimes you may need to ship an item to us for repairs or calibration. Broken glassware is particularly vulnerable to further damage in transit and must be packed with care to protect it and avoid injury to both the packer and whoever unpacks it at the other end. It should be clearly labelled as containing broken glass and the broken glass must be clean. One of the best materials for packing glass is a roll of corrugated cardboard. Wrap the item in multiple layers secured by tape. Make sure the ends of the item are well covered. Then pack into a normal outer carton filled with standard packaging material. The cardboard is rigid enough to resist compression during handling and provides both support and cushioning from sharp impacts. Bubble wrap is also good if it is used in multiple layers to provide a thick cushion.

No, as long as the temperature does not exceed 300 degrees centigrade, which is well above normal autoclaving temperatures.

Volumetric glassware is calibrated in two ways, either to deliver, which measures the volume they deliver, or to contain which measures the volume they contain. For example, a volumetric flask, which is used to make up a specific volume of solution is calibrated to contain and is marked IN or TC. A burette, which is used to measure how much solution has been run out of it, is calibrated to deliver and is marked EX or TD. Glassware designed to deliver accounts for the small amount of solution left on the glass. For example, a 100ml pipette contains a little more than 100ml of liquid but delivers exactly that amount.

A good rule of thumb is that Class A items are usually accurate to 1% of the total volume and class B items are accurate to 2% of the volume. However, this is not always the case as the accuracy of volumetric glassware varies depending on the diameter of the glass at the calibration point and the standard to which the item has been manufactured. The narrower the glass at the calibration point the greater the accuracy achievable. For standard items we list out the tolerances in our catalogue. For customised items we try to stay as close to these as possible by interpolation or extrapolation.

Class A glassware tends to be calibrated to a tighter tolerance than Class B, and Class A is traceable by a unique serial number. We therefore recommend the use of Class A glassware for quantitative work or use in controlled environments and Class B glassware for qualitative work. Calibration Certificates are available on request at the time of purchase for Class A items. We can also issue certificates of accuracy for items sent to our works for checking. Please enquire.

This depends on the diameter of the glass at the calibration mark. There is also a practical limit on the reproducibility of results made by estimates of the position of the meniscus by the human eye. As a rule of thumb 0.5% is the maximum practical accuracy for most items, and this would be beyond what is required for most applications. We would recommend having a conversation with us about accuracy for any tolerance below this.

Always wash glassware before you use it for the first time, or if it has been unused for a while. This will ensure any traces of grease are removed which may interfere with the formation of a good meniscus. Distilled water on the glass should form a smooth layer rather than many discrete droplets.

In controlled environments Class A volumetric glassware should be used and a certificate of accuracy obtained initially and kept for each item of glassware.

We recommend that in a controlled environment the quality manager carry out a simple visual check of glassware in the cabinet every 6 months to­ 1 year depending on the intensity of use. Any items that are chipped, cracked, or severely scratched or cloudy should be discarded. A cloudy item indicates that the surface is being attacked and if this continues for a long time the accuracy may be compromised.

We always recommend that the operator look at the condition of the glassware before using, and any that are chipped or cracked should be disposed of safely.

There is no need to calibrate standard volumetric glassware regularly. A volumetric glass item will still be accurate after many years of proper use. If the glass looks clear and unscratched the volume will not have changed unless the item has been exposed to temperatures of more than 300°C. If they must be rechecked for quality assurance, a 5- or 10-year period between checks is appropriate.

Use laboratory-safe labels or markers that can withstand solvents and heat. Avoid masking tape or paper that can fall off or degrade.

Some high-value glassware can be repaired by a professional glassblower. However, in most cases, replacement is safer and more cost-effective. We can undertake this work, see our breakage service page.

Wear safety goggles, lab coat, and gloves as needed. Use tongs or heat-resistant mitts for hot glassware and inspect all items before use.

Clean thoroughly between uses, especially when switching chemicals. For sensitive work, use dedicated glassware for specific reagents or processes.

Include:

• Chemical name and concentration
• Date prepared
• Initials of preparer
• Hazard information (if applicable)

Use solvent-resistant markers or labels. Some glassware will have a white patch for this purpose and a pencil can be used on this for temporary labels.

In controlled environments Class A volumetric glassware should be used and a certificate of accuracy obtained initially and kept for each item of glassware.

We recommend that in a controlled environment the quality manager carry out a visual check of glassware in the cabinet every 6 months to­ 1 year depending on the intensity of use. Any that are chipped, cracked, or severely scratched or cloudy should be discarded. A cloudy item indicates that the surface is being attacked and if this continues for a long time the accuracy may be compromised.

We always recommend that the operator look at the condition of the glassware before using, and any that are chipped or cracked should be disposed of safely.

There is no need to calibrate standard volumetric glassware regularly. A volumetric glass item will still be accurate after many years of proper use. If the glass looks clear and unscratched the volume will not have changed unless the item has been exposed to temperatures of more than 300°C. If glassware must be rechecked for quality assurance, a 5- or 10-year period between checks is appropriate.

Trading standards are responsible for enforcement of fair trading, and each area has its own office. While we can make some appropriate suggestions, ultimately you will need to check with your local trading standards that what you are proposing is acceptable. You can find your local office here:

https://www.gov.uk/find-local-trading-standards-office

Generally, we would recommend an optic measure for selling alcohol, and an average system measure for selling non-alcoholic liquids. A government stamped conical measure or government stamped cylinder measure may also be acceptable, and of a more practical shape for some applications.

The biggest reason for stuck taps is that the used item is left for days and weeks assembled, and particularly if they have been used with a basic solution, or one with nonpolar solvents that dissolve the grease away in places. Silica then dissolves in the alkali and reforms in the joint, welding the surfaces together. Once this has happened it is very difficult, or impossible to get them apart. Removing them immediately after use normally avoids this problem.

The joint should be disassembled as soon as possible after use, and the grease cleaned off with a paper towel then the item washed. They should be either kept disassembled or reassembled with a small piece of paper as a spacer between the barrel and the key to prevent the two surfaces sticking together.

Make sure the tap is clean. Apply a thin layer directly from the tube to the glass of the key by angling the nozzle. Draw 2 lines of grease diametrically opposite each other from close to the thinnest end of the taper to close to the thickest end of the taper. Avoid the holes in the key. Place the key into the barrel and gently rock it backwards and forwards with gentle pressure. You should see a clear film spreading out until the whole barrel is clear and there are no lines or air bubbles in the joint. If excess grease spills out of the ends of the barrel, wipe it off and use less grease next time. Ground glass joints can be treated in the same way, but avoid using too much grease near the narrow end of the taper as this will potentially contaminate the inside of the apparatus you are assembling.

Getting a ground glass key apart once it has been stuck together is not easy and there is no guarantee of success. It is also very easy to injure yourself, so if someone is going to try, they need to have heavy gloves, eye protection and some practical experience. This is not a job for a beginner! Please make sure that they take care as applying pressure and/or heat to glass can cause it to break unexpectedly and give nasty cuts, burns or worse.

Unfortunately, penetrating solvents like WD40 or oil rarely work here, though you can try using standard penetrating oil rather than silicone-based products. Over time WD40 may make the problem worse as it contains silicone which can decompose and cause further adherence.

First, try applying pressure from the end of the barrel if it is exposed. Remove the plastic keeper and firmly push the narrow end of the glass key directly down onto a wooden block keeping the key vertical. This occasionally will remove the key, but not often. Wood is a good material for working with glass, as it won’t apply thermal shock, or be so hard as to shatter the exposed end of the tap. The next step is to try to apply rapid heat to the barrel, so it expands before the key does. Hot water will rarely do the trick, but it is the first thing to try. Run under the hottest tap for a few seconds, then quickly try the key. Sometimes lightly tapping the key on the wooden block may loosen it at this stage. The next step is to try the same trick but with a paint stripping torch. Same technique. Heat the barrel as quickly as possible then try rapidly to turn and remove the key while wearing a glove. Finally, you can try using a gas torch or Bunsen burner. There is a great risk that the funnel will crack, but by this stage you don’t have much to lose. There is a balance between rapid heating, so the barrel expands, and too rapid heating so the whole thing cracks. Remember to try and remove the key as quickly as possible before the key absorbs the heat and the differential expansion advantage is lost.

A silver preparation is applied to the outside of glass vessels. The vessels are heated and the silver ions diffuse into the glass producing a permanent brown colouration in the glass. There is no residue left on the surface.

All borosilicate and soda glass items can be amberised, though soda glass produces a darker colour, and complex glassware may not amberise evenly. The application process involves moderately high temperatures, so volumetric glassware will need to be checked after amberising to ensure it has remained within the stated tolerances.

Amberised glass reduces the light exposure of the contents of the glassware. Some chemicals are sensitive to light and break down when exposed to it. Amberising helps reduce the rate of this decomposition.

Amberising coating costs depend on the size and shape of the glassware, so please email us at enquiries@jaytecglass.co.uk and we will send you a quote. The silver preparation is expensive, and the process is labour intensive, so the costs rise markedly with the size of the item. You can send us glassware to be amberised, or for more routine items we can source and treat them.

Yes, the amber stain is absorbed into the glass, and will not affect its other physical properties. Amber stained glassware can be washed in a laboratory dishwasher or autoclaved in the same way as ordinary laboratory glassware can.

The actual process takes around 48 hours, but please allow at least 2 weeks for delivery from the order date. If you need a quick turnaround, please contact us. See our Amberising service page for more information.

A non-toxic clear plastic coating applied to the outside of glass vessels.

All glass items can be coated, including borosilicate and soda glass. The application process involves moderately high temperatures, but not enough to distort or melt the glass.

The main reason is for safety. The plastic coating contains the glass in the event of a breakage, making it less likely to scatter broken glass or the contents of the glassware. If the glassware fails, the plastic coating prevents the resulting implosion from scattering glass around the laboratory. A secondary benefit is that the coating gives some protection from impacts, making it less likely to be broken if dropped or knocked. Finally, if the glassware contains a valuable compound, it is more likely to be contained and be retrievable.

No, the glassware should not be autoclaved, microwaved or frozen.

Plastic coating costs depend on the glassware being coated, so please email us at enquiries@jaytecglass.co.uk and we will send you a quote. The costs are quite variable depending on the complexity of the item. You can send us glassware to be coated, or for more routine items we can source them and coat them.

The actual process takes around 24 hours, but please allow at least 2 weeks for delivery. If you need a quick turnaround, please contact us.